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1
Sanson, Alessandra. "Modified bismuth titanate piezoelectric ceramics." Thesis, Cranfield University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401625.
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Duan, Runrun. "High Curie Temperature Bismuth- and Indium- Substituted Lead Titanate." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06082004-124159/unrestricted/Duan%5FRunrun%5F200407%5Fmast.pdf.
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Thesis (M.S.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2005. Directed by Robert Snyder.Shrout, Thomas, Committee Member ; Snyder, Robert, Committee Member ; Speyer, Robert, Committee Chair. Includes bibliographical references.
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Turner, Stuart Lee. "The structure of bismuth ferrite - lead titanate (BiFeO3 - PbTiO3)." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507885.
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Palan, Rohit Chandulal. "Pyroelectric Properties of Ferroelectric Lanthanum Bismuth Titanate Thin Films." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1000746504.
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Burnett, Timothy Laurence. "Growth and charaterisation of bismuth ferrite lead titanate single crystals." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487709.
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Bismuth ferrite lead titanate (BFPT) shows potential in high temperature piezoelectric and ferroelectric applications as well in the emerging field of multiferroic research. Single crystals of (BFPT) have been grown for the first time using the flux growth method.
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Soares-Carvalho, Fernanda. "Elaboration de couches minces ferroélectriques de titanate de bismuth Bi4Ti3O12." Limoges, 1996. http://www.theses.fr/1996LIMOA001.
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Stevenson, Timothy James. "Magnetic and electric properties of bismuth ferrite lead titanate ceramics." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/1371/.
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Solid solutions of multiferroic BiFeO3 doped with ferroelectric PbTiO3 (BFPT) can be prepared by conventional mixed oxide processing to produce a range of polycrystalline ceramics ranging throughout the xBiFeO3 - (1-x)PbTiO3 series. Sintered ceramics are shown to exhibit mixed tetragonal (P4mm) and rhombohedral (R3c) phase perovskite distortions from 0.4 ≤ x < 0.75, where at x ~ 0.75 a morphotropic phase boundary exists and compositions x > 0.75 are entirely rhombohedral. From extensive use of neutron diffraction experiments, the phase coexistence is attributed to compensation for the internal strain induced upon cooling through the ferroelectric Curie point from cubic, to the distorted tetragonal perovskite phase (ܿ/ܽ = 1.17). This drives a further partial transformation to the (~4 %) lower volume rhombohedral phase as a relief mechanism. Increasing the sinter temperature and fast cooling (> 900 °C/hr) sees the monolithic samples x ≤ 0.7 disintegrate to various levels of particulate size, when a critical grain size is exceeded (7 μm), which in turn is inversely proportional to the grain boundary fracture energy. The magnetic properties studied using high resolution powder diffractometry of these two states present G-type antiferromagnetism (AFM) in both the rhombohedral and tetragonal phases; but with Tn above ambient temperature for R3c, and below for P4mm for all compositions except x = 0.3. Compositions below this PbTiO3 rich solution are never observed to support antiferromagnetic order, as the dilution of magnetic iron ions exceeds the percolation threshold via substitution with titanium ions. The rhombohedral phase is shown to exhibit an incommensurate, modulated magnetic order, with a propagation vector perpendicular to the magnetization vector, which decreases in periodicity with increasing bismuth ferrite, from 840 Å for x = 0.75. At room temperature, transforming the paramagnetic tetragonally distorted powder to a G-type AFM rhombohedral phase, is observed with the application of hydrostatic pressure. Evident from neutron experiments, using the Pearl instrument at ISIS, full transformation can be achieved with moderate pressures of 0.77 GPa, effectively ‘switching’ on the magnetic order. The monolithic samples were used at 250 K to observe the changes in simultaneous structural and G-type antiferromagnetic properties as a function of applied electric field (0 to 10 MVm-1) for the most piezoelectrically active samples, around the MPB composition (x = 0.7), using neutron diffraction at the Berlin neutron scattering centre; instrument E2. An observed increase in rhombohedral phase occurs with the application of electric field from peak analysis, which relates to a proportional increase in observed antiferromagnetic intensity (5 %). These two behaviours are proposed to be linked by the internal strain developed within the system, from increased polarisation forcing a partial phase transformation from the tetragonal to the rhombohedral phase which can support the antiferromagnetic order at room temperature.
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Wang, Naigang. "Multiferroic Bismuth Ferrite-Lead Titanate and Iron-Gallium Crystalline Solutions: Structure-Property Investigations." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33854.
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Recently, multiferroics-defined as materials with coexistence of at least two of the ferroelectric, ferroelastic and ferromagnetic effects-have attracted enormous research activities. In this thesis, the structure and properties of multiferrioic BiFeO3-x%PbTiO3 and Fe-x%Ga crystalline solutions were investigated.
First, the results show that modified BiFeO3-PbTiO3 based ceramics have significantly enhanced multiferroic properties, relative to BiFeO3 single crystals. The data reveal: (i) a dramatic increase in the induced polarization; and (ii) the establishment of a remnant magnetization by a breaking of the translational invariance of a long-period cycloidal spin structure, via substituent effects. In addition, temperature dependent magnetic permeability investigations of BiFeO3-xPbTiO3 crystalline solutions have shown that aliovalent La substitution results in a significant increase in the permeability.
Second, room temperature high-resolution neutron and x-ray diffraction studies have been performed on Fe-x%Ga crystals for 12
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Merka, Oliver [Verfasser]. "Yttrium bismuth titanate pyrochlore mixed oxides for photocatalytic hydrogen production / Oliver Merka." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2012. http://d-nb.info/1029589895/34.
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Nahime, Bacus de Oliveira [UNESP]. "Síntese e caracterização estrutural de filmes finos Bi4Ti3O12." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/92018.
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nahime_bo_me_ilha.pdf: 1294512 bytes, checksum: ffc3048caf6b741e23555fbf3b2fbd5e (MD5)Na última década, cresceu consideravelmente o interesse pela produção de filmes finos ferroelétricos, em virtude do grande potencial que estes materiais apresentam para a produção de dispositivos de memória ferroelétrica não-voláteis. O titanato de bismuto, Bi4Ti3O12 (BIT) é um ferroelétrico com estruturas de camadas de bismuto, conhecido por apresentar elevada temperatura de Curie (Tc), próxima de 650ºC, e excelentes propriedades de fadiga ferroelétrica. Este trabalho teve como objetivo a síntese de filmes finos de BIT e o estudo das suas propriedades estruturais. Os filmes estudados foram preparados a partir de um método químico, similar ao método Pechini, e depositados sobre substratos de Si(100). Os filmes foram cristalizados em forno convencional entre 500°C e 700°C, por períodos entre 1 e 12 horas. As técnicas de difração de raios-X (DRX) e Espectroscopia no Infravermelho por Transformada Fourier (FT-IR), foram usadas como ferramentas de investigação. Para os filmes tratados termicamente entre 400°C e 700°C, observouse a presença das fases cristalinas Bi4Ti3O12 e Bi2Ti2O7 (paraelétrica). Para os filmes tratados termicamente a temperaturas mais elevadas (700°C) e tempos mais prolongados (10 horas), observou-se uma tendência de desaparecer a fase Bi2Ti2O17. Aliados a estes resultados, o aumento da intensidade do pico (117) do BIT e o decréscimo da sua respectiva largura a meia altura, para os filmes cristalizados a 700°C, sugerem que nestas condições são obtidos filmes mais bem cristalizados. Um estudo usando a técnica FT-IR demonstrou a presença de uma banda de absorção claramente evidenciada em torno de 700 cm-1. Esta banda está associada ao modo stretching da ligação Ti-O e torna-se consideravelmente mais estreita quando a resina polimérica precursora foi tratada termicamente a temperaturas mais elevadas. Este fato também comprovou que temperaturas em torno de 700°C são favoráveis para a...
In the last decade the interest for the production of ferroelectric thin films increased considerably because of the great potential that these materials present for the production of devices of no-volatile ferroelectric memory. The bismuth titanate, Bi4Ti3O12 (BIT), is a ferroelectric with structures of bismuth layers, known by presenting high temperature of Curie (Tc), close of 650ºC, and excellent properties of ferroelectric fatigue. This work had as objectives the synthesis of thin films of BIT and the study of their structural properties. The studied films were prepared starting from a chemical method, similar to the Pechini method, and deposited on substrata of Si(100). The films were crystallized in conventional oven between 500°C and 700°C for periods between 1 and 12 hours. The techniques of X-ray diffraction (DRX) and Fourier Transform Infrared (FT-IR) Spectroscopy were used as investigation tools. It was observed the presence of the crystalline phases Bi4Ti3O12 and Bi2Ti2O7 (paraelectric) for the films termically treated between 400°C and 700°C. To the films termically treated to higher temperatures (700°C) and more lingering times (10 hours) a tendency of the phase Bi2Ti2O7 to disappear was observed. Allied to these results, the increase of the intensity of the pick (117) of the BIT and the decrease of its respective width to half height, for the crystallized films to 700°C suggests that, in these conditions, better crystallized films are obtained. A study using the FT-IR technique demonstrated the presence of an absorption band clearly evidenced around 700 cm-1. This band is associated to the stretching way of the Ti-O connection and becomes considerably narrower when the precursory polimeric resin was termically treated to higher temperatures. This fact also proved that temperatures around 700°C are favorable for obtaining a mono-crystalline phase of Bi4Ti3O12.
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Spears, Marlene Ann. "Defect chemistry and electrical properties of ruthenium- and bismuth-substituted gadolinium titanate pyrochlore." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11443.
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Sheets, Sossity A. (Sossity Amber) 1973. "Dielectric and electromechanical properties of barium and zirconium co-doped sodium bismuth titanate." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/28621.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000.Includes bibliographical references (p. 175-179).
Compositional exploration was conducted within the alkaline bismuth titanate system by doping on the A- and B- sites with Ba⁺² and Zr⁺⁴, respectively. Results on the phase, dielectric and electromechanical properties of single crystals and polycrystals for this new family of relaxor perovskite ferroelectrics are presented. The actuation and polarization characteristics in this system were found to be highly sensitive (within 2 mol%) to cation doping levels, and tailored compositions successfully isolated predominantly electrostrictive actuation at room temperature. Ultra-high room temperature electrostriction was observed in co-doped (Ba + Zr) NBT polycrystals (NBT-14BT-4NBZ) and <100> single crystals (NBT-12BT-4NBZ), up to 0.24% and 0.45% strain, respectively, with negligible hysteresis at 0.05 Hz. Polycrystals with d₃₃ of up to 780 pC/N and single crystals with d₃₃ up to 2000 pC/N were measured. The low frequency actuation properties in the NBT-BT-NBZ compositions surpass highest reported values of strain and d₃₃ for polycrystalline PMN and PLZT and single crystal PMN conventional lead electrostrictors. Predominantly ferroelectric room temperature unipolar actuation in polycrystalline NBT-14BT-3NBZ at 0.05 Hz was observed to be linear and non-hysteretic, reaching up to 0.14% strain and d₃₃ of 310 pC/N at 60 kV/cm. These low frequency properties match the reported strain and d₃₃ values for conventional PZT-8, PMNT, and PZT-5a hard ferroelectrics and are more than double the reported values for polycrystalline NBT-BT (d₃₃ = 125 pC/N). Electrostrictive and ferroelectric compositions in the NBT-BT-NBZ system show the highest actuation strain and d₃₃ reported to date in any polycrystalline, lead-free composition.
by Sossity A. Sheets.
S.M.
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Matichyn, Serhiy. "Fabrication and characterisation of ferroelectric lead zirconate titanate and strontium bismuth tantalate thin films." [S.l.] : [s.n.], 2006. http://diglib.uni-magdeburg.de/Dissertationen/2006/sermatichyn.htm.
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Qaisar, Sayyed Adam. "Fatigue and high temperature behaviour of the La-doped bismuth-ferrite lead-titanate system." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5556/.
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For the past fifty years, lead zirconate titanate (PZT) has been the material of choice for the piezoelectric industry with piezoelectric materials showing promise in their applicability to smart devices and structures, from adaptive optics to ultrasonics and sonar. The longevity and reliability of PZT is, as with any commercial material, a topic that is well documented with reported operating lifetimes as large as 109 cycles. However PZT is severely limited in the type of thermal environment it can sustainably operate in, with maximum operating temperatures conservatively set around 150°C for commercial materials a new material is required for use in thermally hostile environments. The basic aim of this research was to investigate the performance of 3% La-doped BFPT as a device at high temperatures, fields and stresses in comparison to equivalent PZT materials and further understanding of fatigue in both materials - essential for use of either as a commercially viable device. As no such, readily accessible, apparatus for testing ferroelectric ceramics existed it was essential to first develop the capability before experimentation could begin. Upon development of a suitable apparatus, BFLPT and PZT fatigue studies were conducted and the fatigue as a function of domain contributions investigated using weak-signal measurements in bulk materials. Furthermore, using weak-signal measurements a study of domain behaviour at temperature was sought to give insight into the fundamental behaviour of ferroelectric materials at elevated temperatures - something previously only investigated using the likes of synchrotron facilities, and highlighted previously unobserved contribution changes occurring during material ageing.
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Khan, Mikael Ali. "Preparation and properties of bismuth ferrite-lead titanate thin films prepared by pulsed laser deposition." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485633.
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Development of ferroelectric thin films has been a subject of intensive investigation in recent years due to their promise in next· generation electronic devices. This report encompasses an· initial investigation into the pulsed laser deposition of thin films of bismuth ferrite-lead titanate (l-x)BiFe03-xPbTi03 (BFPT) on platinized silicon (Pt/Si) substrates. The work presented lays down optimised processing conditions for the preparation of BFPT thin films on Pt/Si substrates and presents an understanding of structure-property relationships of this material system thereby providing a firm platform to go forward and exploit this material in various thin film applications, particularly those requiring large remanent polarizations. The growth conditions were optimized by changing a range of process .parameters such as background oxygen pressure, substrate temperature and target to substrate distance which have a critical influence on the film structure and properties. The film structure was studied using X-ray diffraction and scanning electron microscopy. The ferroelectric properties have been presented in terms of typical polarization-field P-E hysteresis behaviour, in conjunction with leakage current measurements and impedance spectroscopy. Investigation into the electrical properties indicates a large increase in the remanent polarization close to the morphotropic phase boundary, making these compositions very attractive for commercial thin film applications e.g. ferroelectric memories.
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Nahime, Bacus de Oliveira. "Síntese e caracterização estrutural de filmes finos Bi4Ti3O12 /." Ilha Solteira : [s.n.], 2007. http://hdl.handle.net/11449/92018.
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Orientador: Eudes Borges de AraújoBanca: Marco Antonio Utrera Martines
Banca: José de los Santos Guerra
Resumo: Na última década, cresceu consideravelmente o interesse pela produção de filmes finos ferroelétricos, em virtude do grande potencial que estes materiais apresentam para a produção de dispositivos de memória ferroelétrica não-voláteis. O titanato de bismuto, Bi4Ti3O12 (BIT) é um ferroelétrico com estruturas de camadas de bismuto, conhecido por apresentar elevada temperatura de Curie (Tc), próxima de 650ºC, e excelentes propriedades de fadiga ferroelétrica. Este trabalho teve como objetivo a síntese de filmes finos de BIT e o estudo das suas propriedades estruturais. Os filmes estudados foram preparados a partir de um método químico, similar ao método Pechini, e depositados sobre substratos de Si(100). Os filmes foram cristalizados em forno convencional entre 500°C e 700°C, por períodos entre 1 e 12 horas. As técnicas de difração de raios-X (DRX) e Espectroscopia no Infravermelho por Transformada Fourier (FT-IR), foram usadas como ferramentas de investigação. Para os filmes tratados termicamente entre 400°C e 700°C, observouse a presença das fases cristalinas Bi4Ti3O12 e Bi2Ti2O7 (paraelétrica). Para os filmes tratados termicamente a temperaturas mais elevadas (700°C) e tempos mais prolongados (10 horas), observou-se uma tendência de desaparecer a fase Bi2Ti2O17. Aliados a estes resultados, o aumento da intensidade do pico (117) do BIT e o decréscimo da sua respectiva largura a meia altura, para os filmes cristalizados a 700°C, sugerem que nestas condições são obtidos filmes mais bem cristalizados. Um estudo usando a técnica FT-IR demonstrou a presença de uma banda de absorção claramente evidenciada em torno de 700 cm-1. Esta banda está associada ao modo "stretching" da ligação Ti-O e torna-se consideravelmente mais estreita quando a resina polimérica precursora foi tratada termicamente a temperaturas mais elevadas. Este fato também comprovou que temperaturas em torno de 700°C são favoráveis para a ...
Abstract: In the last decade the interest for the production of ferroelectric thin films increased considerably because of the great potential that these materials present for the production of devices of no-volatile ferroelectric memory. The bismuth titanate, Bi4Ti3O12 (BIT), is a ferroelectric with structures of bismuth layers, known by presenting high temperature of Curie (Tc), close of 650ºC, and excellent properties of ferroelectric fatigue. This work had as objectives the synthesis of thin films of BIT and the study of their structural properties. The studied films were prepared starting from a chemical method, similar to the Pechini method, and deposited on substrata of Si(100). The films were crystallized in conventional oven between 500°C and 700°C for periods between 1 and 12 hours. The techniques of X-ray diffraction (DRX) and Fourier Transform Infrared (FT-IR) Spectroscopy were used as investigation tools. It was observed the presence of the crystalline phases Bi4Ti3O12 and Bi2Ti2O7 (paraelectric) for the films termically treated between 400°C and 700°C. To the films termically treated to higher temperatures (700°C) and more lingering times (10 hours) a tendency of the phase Bi2Ti2O7 to disappear was observed. Allied to these results, the increase of the intensity of the pick (117) of the BIT and the decrease of its respective width to half height, for the crystallized films to 700°C suggests that, in these conditions, better crystallized films are obtained. A study using the FT-IR technique demonstrated the presence of an absorption band clearly evidenced around 700 cm-1. This band is associated to the stretching way of the Ti-O connection and becomes considerably narrower when the precursory polimeric resin was termically treated to higher temperatures. This fact also proved that temperatures around 700°C are favorable for obtaining a mono-crystalline phase of Bi4Ti3O12.
Mestre
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Steiner, Sebastian [Verfasser], Till [Akademischer Betreuer] Frömling, and Kyle G. [Akademischer Betreuer] Webber. "Defect Chemistry of Sodium Bismuth Titanate and its Solid Solutions / Sebastian Steiner ; Till Frömling, Kyle G. Webber." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1207999822/34.
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Steiner, Sebastian [Verfasser], Till [Akademischer Betreuer] Frömling, and Kyle [Akademischer Betreuer] Webber. "Defect Chemistry of Sodium Bismuth Titanate and its Solid Solutions / Sebastian Steiner ; Till Frömling, Kyle G. Webber." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1207999822/34.
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AMARAL, Thiago Martins. "Estudos da sinterização de Bi12TiO20 (BTO) visando obter cerâmicas transparentes." Universidade Federal de Goiás, 2011. http://repositorio.bc.ufg.br/tede/handle/tde/804.
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Previous issue date: 2011-02-16This work presents the systematic results of studies concerning the sintering of the Bi12TiO20 (BTO) aiming the production of transparent ceramic samples. All that because the BTO is a material that has great scientific and technologic visibility due to its optical, electro and electro-optical properties, but still little explored as ceramic. The sintering starting material was obtained by solid state reaction between Bi2O3 e TiO2; the synthesized BTO was grinded in ball milling until sub micrometric sizes. The conditions for preparing green samples were also investigated, allowing samples with green relative density between 58% and 62%, with uniaxial and isostatic pressing techniques. The study of the sintering process involved different sintering programs, under different atmospheres conditions and additive utilization. Optimized conditions were established and the limiting factors discussed. The quality of the obtained ceramics was assessed by their final relative density, phase homogeneity, microstructure and optical properties (transmission, optical activity and electro-optical performance). Samples with relative density above 99,9% and 50% of the monocrystal´s optical transmission in the 633 nm wavelength and equal optical activity were obtained. Nevertheless, the ceramics still show scattering centers and none liquid electro-optical effect was observed.
Neste trabalho são apresentados resultados de estudos sistemáticos referentes à sinterização do Bi12TiO20 (BTO) visando a obtenção de amostras cerâmicas transparentes. Isso porque o BTO é um material de grande interesse científico e tecnológico devido às suas propriedades ópticas, elétricas e eletroópticas, mas ainda pouco explorado como cerâmica. O material de partida para sinterização foi obtido por reação no estado sólido entre Bi2O3 e TiO2; o BTO assim sintetizado foi moído em moinho de bolas até tamanhos submicrométricos. As condições de preparação de pastilhas a verde foram investigadas, permitindo a obtenção de corpos com densidade relativa a verde, entre 58% e 62%, com uso de prensagem uniaxial e isostática. O estudo do processo de sinterização envolveu avaliar diferentes rampas de aquecimento, atmosfera de sinterização e utilização de aditivos. Condições otimizadas foram estabelecidas e os fatores limitantes discutidos. As cerâmicas foram avaliadas com respeito à densidade relativa final, homogeneidade de fase, microestrutura e propriedades ópticas (transmissividade, atividade óptica e modulação eletro-óptica). Amostras com densidade relativa maior que 99,9%, transmitância óptica de até 50% daquela do monocristal em 633 nm e atividade óptica idêntica foram obtidas. No entanto, as cerâmicas ainda apresentam centros espalhadores e nenhum efeito líquido de modulação eletro-óptica foi observado.
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Lee, Sung-Kyun. "Growth, microstructure and ferroelectric properties of non-c-axis-oriented rare earth substituted bismuth titanate thin films and nanostructures." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=980161304.
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Coathup, David James. "The effect of interface layers and doping on the multiferroic properties of bismuth titanate oxide thin films on silicon." Thesis, Aston University, 2017. http://publications.aston.ac.uk/38210/.
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For the development of magnetoelectric memory devices, the development of artificial magnetoelectric materials is necessary. Previous work in the field had focused on the multiferroic properties of this material in bulk form, however, for a practical device, a thin film investigation is needed. This thesis details the author's investigation into the multiferroic properties of bismuth titanate oxide, Bi4Th012, (BTO) thin films doped with lanthanum, niobium, iron and cobalt, to form the novel material Bi3.2slao.7sLTb.sNbo.2sFeo.mCoo.m012 (BTFC), and how different interface layers influence their structural and electronic properties when they are deposited on silicon substrates. The aim of this research is to achieve a multiferroic BTO thin film with strong ferroelectric and ferromagnetic properties by utilising a novel combination of dopants. Chapter 1is the introduction, providing insight into the layout and structure of the thesis making it easier for the reader to follow. Chapter 2 is the background literature review, which discusses the real life industrial demands of this work, and is followed by a discussion of the physics and material science principles behind this investigation. Chapter 3 is the experimental literature review, in which the material synthesis, device fabrication and characterisation techniques utilised in this work are discussed. The experimental chapters begins with Chapter 4, in which the effect of a zinc oxide (ZnO) interface layer on crystalline properties of BTFC on silicon is investigated. Chapter 5 follows this investigation up by investigating ferroelectric propertied of BTFC thin films on silicon with ZnO interface layers. Finally chapter 6 looks at BTFC thin films on silicon substrates with platinum interface layers, and both simultaneous ferroelectric and ferromagnetic properties were present, confirming multiferroic behaviour. Initial investigations into the deposition onto silicon were unsuccessful, but were overcome by utilising ZnO interface layers. The ZnO interface layer eliminated some critical difficulties; however high resolution transmission electron microscopy (HRTEM) analysis showed zinc atoms from inside the interface layer diffusing into the BTFC thin film. The investigation into the ferroelectric properties of thin films using the triangular voltage waveform method confirmed ferroelectric domain switching, but were inhibited by the need for a vacuum annealing environment to prevent the oxidation of the silicon substrate. This resulted in the generation of oxygen vacancies within the BTFC thin film, which limited driving voltage during the measurement, presenting ferroelectric saturation. The final investigation was focused on BTFC deposited on platinised-silicon substrates. Platinum is proved to be the superior interface layer, due to its chemical and thermal stability. The investigation found high quality crystalline BTFC, with a high dielectric constant and leakage current, which can be attributed to the doping effect. The ferroelectric measurements demonstrated a fully saturated ferroelectric loop, and a remnant polarisation and coercivity of 2Pr = 11.03!lC/cm 2, and 2Ec = 196.5kV/em on the optimised thin films. Ferromagnetic measurements of the sample were challenging, due to the small total magnetisation of the thin film resulting from its low volume and mass. Using a Superconducting Quantum User Interface Device {SQUID) vibrating sample microscopy {VSM), Ferromagnetisum was presented in the bulk and thin film form, however, the remnant magnetisation of the thin film could not be determined, due to its noise level value. This discovery proves the existence of simultaneous ferroelectric and ferromagnetic phases in BTFC thin film, confirming muitiferroic behaviour of the deposited thin films had been achieved with the chosen dopants.
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Schmitt, Veronika [Verfasser], and Josef [Akademischer Betreuer] Breu. "Effect of Dopants on the Local Atomic Structure and Sintering Behavior of Bismuth Sodium Titanate / Veronika Schmitt. Betreuer: Josef Breu." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1059352346/34.
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Dittmer, Robert [Verfasser], Jürgen [Akademischer Betreuer] Rödel, and Karsten [Akademischer Betreuer] Albe. "Lead-Free Piezoceramics – Ergodic and Nonergodic Relaxor Ferroelectrics Based on Bismuth Sodium Titanate / Robert Dittmer. Betreuer: Jürgen Rödel ; Karsten Albe." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2013. http://d-nb.info/1107771757/34.
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Pacher, Fernandes Rodrigo [Verfasser]. "Piezoresponse Force Microscopy study of potassium sodium niobate and bismuth sodium titanate based lead-free ferroelectric materials / Rodrigo Pacher Fernandes." München : Verlag Dr. Hut, 2014. http://d-nb.info/1049362829/34.
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Gatsa, Oleksandr. "Development of acoustic sensors for the extension of measurements to high temperature in the experimental reactors." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS092/document.
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Ce travail de thèse porte sur l’étude et la réalisation d'une nouvelle génération de capteurs ultrasonore dédiés à la caractérisation des gaz de fission. Plus généralement, ces études concernent le développement de l’instrumentation du réacteur d’essai des matériaux Jules Horowitz (RJH), visant entre autre à effectuer le contrôle in situ de la composition du gaz libéré afin d’optimiser la durée de vie du combustible et le taux de combustion. La température de fonctionnement de ce nouveau réacteur devant se situer dans la plage entre 200 °C à 400 °C, la principale problématique concerne donc le développement d’un matériau piézoélectrique, capable de fonctionner dans la plage de température requise, et son intégration à un dispositif de détection.Nous proposons l’utilisation du sodium titanate de bismuth (NBT) développé par la méthode de la sérigraphie. Dans le but d'optimiser les conditions de fabrication des matériaux, plusieurs versions de matériaux piézoélectriques ont été produites au cours de cette thèse. Chacun des matériaux a été caractérisé (paramètres morphologiques, chimiques, électriques, diélectriques, piézoélectriques et électromécaniques) et des tests en fonction de la température ont été conduits. Après avoir démontré une bonne répétabilité dans la production du matériau, le protocole de fabrication des capteurs a été déterminé et un prototype de capteur ultrasonore a été réalisé.Ces capteurs ont été fabriqués par dépôt du matériau actif sur un substrat d'alumine. Après caractérisation des propriétés des capteurs, des essais ont montré une sensibilité acoustique importante à température ambiante. De plus, la possibilité d'une détection de gaz sur une gamme de pression de 50 à 70 bars a été démontrée par l'intégration d’un capteur dans une enceinte. Pour vérifier la possibilité d'application du capteur à la détection de gaz dans des environnements hostiles (haute température), un modèle théorique basé sur les propriétés électromécaniques et les équations d’adaptation d’impédance a été introduit. Il a été démontré théoriquement que le capteur est capable d'effectuer des mesures de gaz de la température ambiante jusqu’à 350 °CThis Ph.D. thesis is dedicated to the development of a new generation of ultrasonic sensors devoted to fission gas characterization. More generally, these studies concern the development of instrumentation for the Jules Horowitz material testing reactor (JHR) aiming to perform in-situ control of the released gas composition for optimization of burn-up rate and fuel rod lifetime. The operation temperature of this new reactor will be in the range of 200 °C - 400 °C. Hence, the main problem concerns the development of piezoelectric material, able to operate in the required temperature range, and its integration with a sensor device.To resolve this problem, we propose to use the sodium bismuth titanate (NBT) ceramic material developed by the screen-printing technique. Several versions of piezoelectric materials were produced during this research, with the purpose of optimizing material manufacturing conditions Each material was characterized (morphological, chemical, electric, dielectric, piezoelectric and electromechanical parameters) and “tests as a function of temperature” were carried out. After demonstrating repeatability in material fabrication, the protocol for NBT sensor production was determined and a prototype of the ultrasonic sensor was fabricated.The sensor was fabricated by deposition of an active material onto an alumina substrate. After characterization of sensor properties, acoustic tests showed a high sensitivity of measurements at ambient temperature (25 °C). Furthermore, by integration of sensors into a pressurized enclosure the possibility of gas detection in the range from 50 to 70 bars was demonstrated. To verify the sensor’s applicability to gas detection under harsh temperature environment, a theoretical model based on electromechanical properties and impedance matching equations was introduced. It was theoretically demonstrated that the sensor is able to perform gas measurements from ambient temperature up to 350 °C
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Schuisky, Mikael. "CVD and ALD in the Bi-Ti-O system." Doctoral thesis, Uppsala University, Department of Chemistry, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-552.
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Bismuth titanate Bi4Ti3O12, is one of the bismuth based layered ferroelectric materials that is a candidate for replacing the lead based ferroelectric materials in for instance non-volatile ferroelectric random access memories (FRAM). This is due to the fact that the bismuth based ferroelectrics consists of pseudo perovskite units sandwiched in between bismuth oxide layers, which gives them a better fatigue nature.
In this thesis thin films of Bi4Ti3O12 have been deposited by chemical vapour deposition (CVD) using the metal iodides, BiI3 and TiI4 as precursors. Films grown on MgO(001) substrates were found to grow epitaxially. The electrical properties were determined for films grown on Pt-coated silicon and good properties such as a high dielectric constant (ε) of 200, low tan δ of 0.018, a remnant polarisation (Pr) of 5.3 μC/cm2 and coercive field (Ec) as high as 150 kV/cm were obtained. Thin films in the Bi-Ti-O system were also deposited by atomic layer deposition (ALD) using metalorganic precursors.
In addition to the ternary bismuth titanates, films in the binary oxide systems i.e. bismuth oxides and titanium oxides were deposited. Epitaxial TiO2 films were deposited both by CVD and ALD using TiI4 as precursor. The rutile films deposited by ALD were found to grow epitaxially down to a temperature of at least 375 ¢ªC on α-A12O3(0 1 2) substrates. The TiO2 ALD process was also studied in-situ by QCM. Different bismuth oxides were deposited by halide-CVD using BiI3 as precursor on MgO(0 0 1) and SrTiO3(0 0 1) substrates and the results were summarised in an experimental CVD stability diagram. The Bi2O2.33 phase was found to grow epitaxially on both substrates.
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Vijay, Dilip P. "Reliability and processing of ferroelectric thin film capacitors with emphasis on fatigue and etching." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-162341/.
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Bousquet, Marie. "Croissance, caractérisations et étude des propriétés physiques de films minces du matériau ferroélectrique Na0,5Bi0,5TiO3." Limoges, 2010. http://aurore.unilim.fr/theses/nxfile/default/43e4e73f-32af-463d-9709-401209acea22/blobholder:0/2010LIMO4062.pdf.
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Ce travail est consacré à l'élaboration par ablation laser et à la caractérisation de couches minces épitaxiées du matériau ferroélectrique sans plomb Na0,5Bi0,5TiO3 (NBT). Dans un premier temps, nous avons déterminé les conditions de synthèse de couches minces monophasées de NBT, étape délicate où un contrôle rigoureux de la composition chimique est nécessaire afin d'éviter l'apparition de phases secondaires (pyrochlore, phases d'Aurivillius. . . ). Les premières mesures électriques macroscopiques et à l'échelle locale ont permis d'attester du comportement ferroélectrique des films préparés, validant ainsi nos conditions de synthèse. Dans un second temps, la recherche systématique d'une croissance épitaxiale a été visée. Pour atteindre cet objectif, divers substrats monocristallins (Al2O3, MgO. . . ) ont été utilisés, dans une logique de compatibilité avec des applications futures dans le domaine de l'optique et des hyperfréquences. En particulier, les propriétés physiques (optiques et hyperfréquences) d'une couche mince de NBT épitaxiée sur MgO ont été déterminées. En outre, l'utilisation d'électrodes de platine présentant différentes orientations (i. E. , (100), (110), et (111)) ont permis de moduler l'orientation de NBT et d'accéder partiellement à l'anisotropie des propriétés (principalement électriques) du matériau élaboré. En d'autres termes, cette étude a permis de mettre en exergue des relations orientation/microstructure/propriétés électriques locales et macroscopiques, particulièrement intéressantes pour ces films de NBTThe present work is devoted to the growth and the characterizations of epitaxial lead-free ferroelectric Na0. 5Bi0. 5TiO3 (NBT) thin films obtained by Pulsed Laser Deposition (PLD). In a first step, the growth deposition parameters were determined in order to obtain single-phased NBT thin films. Thus, a careful control of the chemical composition is required to elaborate single-phased NBT thin films to avoid the formation of many secondary phases (pyrochlore, Aurivillius phases…). The preliminary room temperature macroscopical hysteresis loops and piezoforce microscopy study testify to the ferroelectric activity of the elaborated material. In a second step, an epitaxial growth of NBT thin films was systematically encountered. For such purpose, various single crystals (Al2O3, MgO. . . ) consistent with the field of optical and microwave measurements were used. In particular, the physical properties (optical and microwave) of an epitaxial NBT thin films deposited on MgO were determined. Moreover some platinum bottom electrodes presenting various orientations (i. E. , (100), (110), and (111)) were employed in order to partially access the anisotropy of the properties (mainly electrical). In other words, this study permits to underline some relationships between the orientation, the microstructure and the macroscopical and local properties, particularly interesting for these NBT thin films
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Wollmann, Philipp. "Synthese und Funktion nanoskaliger Oxide auf Basis der Elemente Bismut und Niob." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-85784.
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Am Beispiel von ferroelektrischen Systemen auf Bismut-Basis (Bismutmolybdat, Bismutwolframat und Bismuttitanat) und von Strontiumbariumniobat werden neue Möglichkeiten zur Synthese solcher Nanopartikel aufgezeigt. Die Integration der Nanopartikel in
transparente Nanokompositmaterialien und die Entwicklung neuer Precursoren für die Herstellung von Dünnschichtproben gehen den Untersuchungen zur Anwendung als elektrooptische aktive Materialien voraus.
Durch weitere Anwendungsmöglichkeiten in der Photokatalyse, dem Test dampfadsorptiver Eigenschaften mit Hilfe eines neuartigen Adsorptionstesters (Infrasorb) und auch mit Hilfe der Ergebnisse der ferroelektrischen Charakterisierung von gesinterten Probenkörpern aus einem Spark-Plasma-Prozess wird ein gesamtheitlicher Überblick über die vielfältigen Aspekte in der Arbeit mit nanoskaligen, ferroelektrischen Materialien gegeben.
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Mathey, Pierre. "Développement d'une nouvelle méthode d'amplification et optimisation des amplificateurs photo réfractifs d'images : application a la déflexion de faisceaux." Phd thesis, Université Paris Sud - Paris XI, 1992. http://pastel.archives-ouvertes.fr/pastel-00714198.
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Cette étude s'attache a l'optimisation de faisceaux par mélange a deux ondes dans des cristaux photorefractifs et a leur emploi dans des dispositifs d'amplification d'images et dans un système de déflexion. Dans un premier temps, nous démontrons que l'application au cristal d'un champ électrique pulse périodique renforce le transfert d'énergie dans le mélange a deux ondes. L'étude analytique du phénomène montre que la technique des champs pulses permet de dépasser la limite d'amplification commune aux autres méthodes d'amplification. Cette technique ne permet pas cependant d'amplifier simultanément toutes les fréquences spatiales d'une image de haute résolution. Pour étudier l'amplification d'images, nous avons employé la technique classique du mélange a deux ondes sous champ alternatif carre. L'examen théorique et expérimental de l'amplification nous permet d'optimiser la forme du champ électrique a appliquer et la nature du dopage du cristal a employer pour obtenir une image amplifiée de haute résolution. Ensuite, nous concevons un système de déflexion de faisceaux s'intégrant dans un dispositif de commutation holographique. Les principaux éléments du système (cristal amplificateur de titanate de baryum et matrice de microlentilles) sont étudiés. On s'intéresse aux aberrations optiques, aux mécanismes physiques responsables du bruit dans le cristal photorefractif et on montre comment réduire ces sources de bruit. Enfin, nous présentons des amplifications d'images dans différents cristaux photorefractifs. Nous comparons les amplifications, les résolutions et les rapports signal a bruit obtenus dans différents échantillons de bi12geo20 et un échantillon de batio3.
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Aguiar, Ederson Carlos de [UNESP]. "Desenvolvimento de cerâmicas texturizadas de titanato de bismuto puro e dopado com nióbio." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/102560.
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No presente trabalho foram preparados pós cerâmicos de Bi4Ti3O12 estequiométrico, com excesso de bismuto e com excesso dopados com nióbio pelo método dos precursores poliméricos. As fases cristalinas foram obtidas por calcinação a 700 °C-4h com 10% excesso Bi nas composições Bi4Ti3-xNbxO12 (x = 0; 0,1; 0,2 e 0,4 mol% Nb). Os pós obtidos foram caracterizados quanto ao tamanho das partículas, difratometria de raios X, espectroscopias Raman, no infravermelho e UV-vis indicando pós nanométricos com fase ortorrômbica predominante, ordenados a curta e longa distância e com alta cristalinidade. As cerâmicas foram compactadas e sinterizadas em forno convencional e microondas a 800 °C, além de caracterizadas por medidas de condutividade elétrica, constante e perda dielétricas, histerese e microscopia eletrônica de varredura. A condutividade elétrica sofreu decréscimo nas cerâmicas dopadas com nióbio, apresentando constante dielétrica de 170 na temperatura ambiente, baixos valores de polarização remanescente e densidade relativa máxima de 93% para cerâmicas sinterizadas em microondas. Cerâmicas funcionais texturizadas foram obtidas empregando-se a técnica de tape casting (colagem de folhas), onde partículas templates do BIT sintetizadas via método dos sais fundidos e com alta orientação na direção do eixo c foram adicionados as barbotinas aquosas do titanato de bismuto. As medidas de caracterização indicaram grau de texturização das cerâmicas de até 80% na direção do eixo c, com aumento da densidade relativa (97%) , da polarização remanescente (3,4 µC/cm2 ) além de menor condutividade elétrica, boa resposta dielétrica e microestrutura com grãos orientados, em comparação às cerâmicas policristalinas
In the present study were prepared stoichiometric Bi4Ti3O12 ceramic powders, with excess bismuth and niobium doped from polymeric precursor method. The crystalline phases were obtained by calcination at 700 °C for 4h with 10% excess Bi in the compositions Bi4Ti3- xNbxO12 (x = 0, 0.1, 0.2 and 0.4 mol% Nb). The powders were characterized for particle size, X-ray diffraction, Raman, IR and UV-vis spectroscopy indicating a predominant nanosized orthorhombic phase ordered at short and long distances, with high crystallinity. The ceramics were compacted and sintered in a conventional and microwave oven at 800 °C, and characterized by measurements of electrical conductivity, dielectric constant and loss, hysteresis, and scanning electron microscopy. The electrical conductivity decreased in the niobium-doped ceramics, with dielectric constant of 170 at room temperature, low remanent polarization and relative density of up to 93% for ceramics sintered in the microwave oven. Functional textured ceramics were obtained using the tape casting methodology where particles of the BIT templates synthesized from the molten salts method presented high orientation in the c-axis direction were added to the aqueous slurry of bismuth titanate. Characterization measures indicated texturing degree of ceramics up to 80% along the c- axis, with increasing in relative density (97%), in the remanent polarization (3.4 µC/cm2) and lower electrical conductivity, good dielectric response and microstructure with grain oriented compared to polycrystalline ceramics
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Aguiar, Ederson Carlos de. "Desenvolvimento de cerâmicas texturizadas de titanato de bismuto puro e dopado com nióbio /." Araraquara : [s.n.], 2009. http://hdl.handle.net/11449/102560.
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Orientador: José Arana VarelaBanca: Mário Cilense
Banca: Valmor Roberto Mastelaro
Banca: Daniel Zanetti de Flório
Banca: Eliana Navarro dos Santos Muccillo
Resumo: No presente trabalho foram preparados pós cerâmicos de Bi4Ti3O12 estequiométrico, com excesso de bismuto e com excesso dopados com nióbio pelo método dos precursores poliméricos. As fases cristalinas foram obtidas por calcinação a 700 °C-4h com 10% excesso Bi nas composições Bi4Ti3-xNbxO12 (x = 0; 0,1; 0,2 e 0,4 mol% Nb). Os pós obtidos foram caracterizados quanto ao tamanho das partículas, difratometria de raios X, espectroscopias Raman, no infravermelho e UV-vis indicando pós nanométricos com fase ortorrômbica predominante, ordenados a curta e longa distância e com alta cristalinidade. As cerâmicas foram compactadas e sinterizadas em forno convencional e microondas a 800 °C, além de caracterizadas por medidas de condutividade elétrica, constante e perda dielétricas, histerese e microscopia eletrônica de varredura. A condutividade elétrica sofreu decréscimo nas cerâmicas dopadas com nióbio, apresentando constante dielétrica de 170 na temperatura ambiente, baixos valores de polarização remanescente e densidade relativa máxima de 93% para cerâmicas sinterizadas em microondas. Cerâmicas funcionais texturizadas foram obtidas empregando-se a técnica de tape casting (colagem de folhas), onde partículas templates do BIT sintetizadas via método dos sais fundidos e com alta orientação na direção do eixo c foram adicionados as barbotinas aquosas do titanato de bismuto. As medidas de caracterização indicaram grau de texturização das cerâmicas de até 80% na direção do eixo c, com aumento da densidade relativa (97%) , da polarização remanescente (3,4 µC/cm2 ) além de menor condutividade elétrica, boa resposta dielétrica e microestrutura com grãos orientados, em comparação às cerâmicas policristalinas
Abstract: In the present study were prepared stoichiometric Bi4Ti3O12 ceramic powders, with excess bismuth and niobium doped from polymeric precursor method. The crystalline phases were obtained by calcination at 700 °C for 4h with 10% excess Bi in the compositions Bi4Ti3- xNbxO12 (x = 0, 0.1, 0.2 and 0.4 mol% Nb). The powders were characterized for particle size, X-ray diffraction, Raman, IR and UV-vis spectroscopy indicating a predominant nanosized orthorhombic phase ordered at short and long distances, with high crystallinity. The ceramics were compacted and sintered in a conventional and microwave oven at 800 °C, and characterized by measurements of electrical conductivity, dielectric constant and loss, hysteresis, and scanning electron microscopy. The electrical conductivity decreased in the niobium-doped ceramics, with dielectric constant of 170 at room temperature, low remanent polarization and relative density of up to 93% for ceramics sintered in the microwave oven. Functional textured ceramics were obtained using the tape casting methodology where particles of the BIT templates synthesized from the molten salts method presented high orientation in the c-axis direction were added to the aqueous slurry of bismuth titanate. Characterization measures indicated texturing degree of ceramics up to 80% along the c- axis, with increasing in relative density (97%), in the remanent polarization (3.4 µC/cm2) and lower electrical conductivity, good dielectric response and microstructure with grain oriented compared to polycrystalline ceramics
Doutor
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Vögler, Malte [Verfasser], Jürgen [Akademischer Betreuer] Rödel, and Bai-Xiang [Akademischer Betreuer] Xu. "Mechanisches Verhalten von Natrium-Bismut-Titanat Piezokeramiken / Malte Vögler ; Jürgen Rödel, Bai-Xiang Xu." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/1162621699/34.
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Nogueira, André Esteves. "Síntese e propriedades fotocatalíticas do titanato de bismuto obtido pela rota dos complexos oxidantes de peróxido." Universidade Federal de São Carlos, 2014. https://repositorio.ufscar.br/handle/ufscar/6321.
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Previous issue date: 2014-08-14Universidade Federal de Minas Gerais
The welfare of the population and technological progress of our society largely depend on the development and the intensive use of synthetic materials, generating a large amount of residual chemicals and high energy consumption. Therefore, the need for development of synthesis routes that are more efficient, economic and environmentally sustainable, both for obtaining new materials as well as for improvement of those traditionally used by the productive sector, has grown in importance. Therefore, the study aimed to understand and extend the use of the oxidant peroxide method (OPM), as a new synthesis route for obtaining bismuth titanate with the sillenite (Bi12TiO20) and perovskite (Bi4Ti3O12) phase. In addition, we studied the influence of defects formed in the structure by the introduction of dopants such as niobium, lanthanum, and lead. These changes were made to obtain materials with improved structural and optical properties for use in the photodegradation process of the organic dye rhodamine B (RhB) under ultraviolet and visible radiation. Through obtaining the amorphous precipitate by the OPM route we observed the formation of spheres of bismuth oxide (Bi2O3) with titanium dioxide (TiO2) nanoparticles with surface peroxo groups that were identified as mainly responsible for the high reactivity of the powders obtained by this synthesis method. The photocatalytic properties of all materials were evaluated by the discoloration of RhB solution under UV and visible irradiation, where the bismuth titanate obtained by the OPM route showed higher photocatalytic activity than the commercial TiO2. Obtaining bismuth titanate calcined at different temperatures allowed the understanding of the effects of crystallinity on the photocatalytic activity. Furthermore, it was observed that the insertion of different ions in the bismuth titanate (Bi12TiO20) structure modified the band gap energy in different ways, which consequently altered the photocatalytic activities of the materials, showing the dependence of the redox potential of the conduction and valence band in the photocatalysis process.
O bem estar da população e o progresso tecnológico de nossa sociedade dependem, em grande parte, do desenvolvimento e do intensivo uso de materiais sintéticos, o que gera um grande volume de resíduos químicos e um elevado consumo de energia. Portanto, a necessidade do desenvolvimento de rotas de síntese que sejam mais eficientes, econômicas e ambientalmente sustentáveis, tanto para a obtenção de novos materiais, quanto para o aperfeiçoamento daqueles tradicionalmente utilizados pelo setor produtivo, tem crescido em importância. Desta forma, o trabalho visou compreender e ampliar o uso do método dos complexos oxidantes de peróxido (OPM), como uma nova rota de síntese para a obtenção do titanato de bismuto com a fase selenita (Bi12TiO20) e perovskita (Bi4Ti3O12). Além disso, avaliou-se a influência dos defeitos formados na estrutura dos materiais pela adição de diferentes dopantes como: nióbio, lantânio e chumbo. Essas modificações foram realizadas a fim de obter materiais com melhores propriedades estruturais e ópticas para aplicação no processo de fotodegradação do corante orgânico rodamina B (RhB) sob radiação ultravioleta (UV) e visível. Através da obtenção dos precipitados amorfos pela rota OPM observou-se a formação de esferas de óxido de bismuto (Bi2O3) juntamente com nanopartículas de dióxido de titânio (TiO2) com grupos peroxos superficiais que foram identificados como os grandes responsáveis pela elevada reatividade dos pós obtidos por este método de síntese. As propriedades fotocatalíticas de todos os materiais foram avaliadas através da descoloração da solução de RhB sob irradiação de luz UV e visível, no qual os titanatos de bismuto obtidos pela rota OPM apresentaram atividades fotocatalíticas superiores ao TiO2 comercial. A obtenção do titanato de bismuto tratado termicamente em diferentes temperaturas permitiu o entendimento dos efeitos da cristalinidade sobre a atividade fotocatalítica. Além disso, observou-se que a inserção de diferentes íons na estrutura do titanato de bismuto (Bi12TiO20) alterou de maneiras diferentes a energia do band gap, que consequentemente alterou as atividades fotocatalíticas dos materiais, deixando clara a dependência dos potenciais redoxes da banda de condução e de valência no processo de fotocatálise.
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Elkechai, Omar. "Céramiques ferroélectriques dans les systèmes NaBiTiO3 - KBiTiO3,NaBiTiO3 - PbTiO3 et KBiTiO3 - PbTiO3." Limoges, 1995. http://www.theses.fr/1995LIMO0018.
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Ce travail concerne l'elaboration et les caracterisations structurales, electriques et piezoelectriques des compositions ceramiques appartenant aux systemes: (nbt - kbt) na#(#0#. #5#)k#xbi#0#. #5tio#3 (0 x 0. 08 ; 0. 3 x 0. 5) (nbt - pt) (na#0#. #5bi#0#. #5)#(#1#-#x#)pb#xtio#3 (0 x 0. 1 ; 0. 18 x 1) (kbt - pt) (k#0#. #5bi#0#. #5)#(#1#-#x#)pb#xtio#3 (0 x 1) la synthese des solutions solides est realisee sous forme de poudre polycristalline par reaction a l'etat solide. L'etude par diffraction x a permis d'etablir l'evolution structurale de ces compositions ainsi que les domaines d'existence des diverses solutions solides. La densification des ceramiques a ete realisee par frittage naturel et par forgeage a chaud. L'etude dielectrique a mis en evidence le caractere ferroelectrique des compositions etudiees, la presence a haute temperature d'une conductivite non negligeable dont les variations sont thermiquement activees et pour certaines solutions solides, une forte dispersion de la permittivite dans le domaine paraelectrique suggerant un phenomene de relaxation dipolaire qui disparait progressivement lors de recuits successifs. L'etude de la transition ferroelectrique-paraelectrique a ete conduite par diffraction x en fonction de la temperature, par calorimetrie differentielle a balayage et par mesure des variations thermiques de la permittivite dielectrique. Les resultats obtenus sont en bon accord et ont permis de proposer un diagramme de phase des systemes etudies. L'etude des caracteristiques piezoelectriques par piezometrie et spectroscopie d'impedance montre que, comme pour les pzt, les meilleures valeurs des constantes piezoelectriques sont obtenues pour les compositions situees a l'extremite du domaine monophase rhomboedrique des systemes (nbt-kbt) et (nbt-pt)
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BONTURIM, EVERTON. "Controle de propriedades multiferroicas em filmes finos óxidos dopados com íons terras raras para aplicação como dispositivos lógicos e de memória." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28033.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Nas últimas décadas, o consumo de dispositivos eletrônicos e a alta demanda por armazenamento de dados tem mostrado grandes oportunidades para a criação de novas tecnologias que garantam as necessidades mundiais na área de computação e desenvolvimento. Alguns materiais multiferroicos tem sido amplamente estudados e o BiFeO3, considerado o único material multiferroico em temperatura ambiente, ganhou destaque como candidato para produção de dispositivos lógicos e de memória. O uso de técnicas de crescimento como a deposição por laser pulsado permitiu a produção de filmes finos de BiFeO3 com elevado controle de qualidade. Heteroestruturas de filmes multiferroicos de BiFeO3 e LaBiFeO3 foram crescidas com diferentes espessuras sobre substratos de SrTiO3(100), DyScO3(110) e SrTiO3/Si(100) para avaliação e teste de suas propriedades elétricas e magnéticas. Filmes ferromagnéticos de Co0,9Fe0,1 foram depositados por sputtering sobre os filmes multiferroicos para avaliação da interação interfacial entre ordenamentos magnéticos. Técnicas como fotolitografia foram utilizadas para padronização de microdispositivos gravados sobre as amostras. Tanto os filmes finos de BiFeO3 como os de LaBiFeO3 foram crescidos epitaxialmente sobre os substratos já cobertos com uma camada buffer de SrRuO3 usado como contato elétrico inferior. A estrutura cristalina romboédrica das ferritas de bismuto foi confirmada pelos dados de difração de raios X, bem como a manutenção de tensão estrutural causada pela rede cristalina do substrato para amostras de 20 nm. Os valores de coeficiente do tensor piezelétrico d33 foram da ordem de 0,15 V (∼ 60 kV.cm-2) para amostras com 20 nm de espessura enquanto que os valores de voltagem coerciva para as análises de histerese elétrica foram da ordem de 0,5 V para as mesmas amostras. A relação de coercividade elétrica com a espessura corresponde ao perfil encontrado na literatura pela relação E≈d-2/3. As amostras de CoFe/BFO e CoFe/LBFO depositadas em diferentes substratos apresentam acoplamento interfacial entre ordenamento ferromagnético e antiferromagnético com momento ferromagnético de rede.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
CAPES:99999.009511/2014-08
CNPq:146622/2013-2
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Ferreira, Rudson da Conceição. "Produção de BI4TI3O12 via rota sol-gel modificada." Pós-Graduação em Física, 2013. https://ri.ufs.br/handle/riufs/5308.
Full textAbstract:
The main goal of this study was to develop a methodology for the production of Bismuth Titanate ceramics in the phase Bi4Ti3O12, based on sol-gel route and using polyvinyl alcohol (PVA) as polymerizing agent. Bi4Ti3O12 is a ferroelectric material with great technological appeal due to its potential application in capacitors and memory devices. Moreover, the sol-gel route with PVA, besides enabling particle size control and low contamination during the synthesis, has the advantage of using less expensive reagents than those used in conventional route. The results indicated that ceramic bodies with single phase and relative density of 70% can be obtained after calcination at 800º C and sintering at 1000º C for 2h. These ceramic bodies had microstructure with sub-micrometric rounded grains that assume platelet morphology when reach micrometric dimensions. The impedance diagram of sintered ceramics presented two characteristic semicircles, thermally activated conductivity and dielectric permittivity
characterized by a dispersion at low frequencies due to charge carriers movement in the material. The activation energy for the conductive processes was determined by the low frequency dependence of electric conductivity and modulus on the temperature. In both cases, it was
observed an Arrhenius-type behavior with energies around 0.7 eV. Similar values were obtained for the conductive processes in intra-grain region, at high frequencies. In this case, the energies were obtained only by analyzing the electrical module. The results obtained point out to the
success of the technique to obtain material with good crystallographic quality through a route that is simplified and cost reduced. In the specific case of the material being studied in this work, additional efforts will be required to achieve ceramics with relative density higher than 90%.O principal objetivo deste trabalho foi o desenvolvimento de uma metodologia para a produção de cerâmicas de Titanado de Bismuto na fase Bi4Ti3O12, baseada na rota de sol-gel e utilizando polivinil álcool (PVA) como agente polimerizante. O Bi4Ti3O12 é um material ferroelétrico com grande apelo tecnológico devido ao seu potencial de aplicação em capacitores e elementos de memória. Por outro lado, a rota de sol-gel com PVA, além de possibilitar o controle de tamanhos de partícula e reduzir riscos de contaminação durante a síntese, apresenta a vantagem de utilizar reagentes de custo menor do que os que são utilizados na rota convencional. Os resultados obtidos indicaram que corpos cerâmicos com fase cristalina única e densidade relativa de 70 % podem ser obtidos após calcinação em 800º C e sinterização a 1000º C por 2h. Estes corpos cerâmicos apresentaram microestrutura com grãos sub-micrométricos arredondados, evoluindo para grãos em forma de plaquetas ao atingir dimensões micrométricas. O diagrama de impedância das cerâmicas sinterizadas apresentou dois semicírculos característicos, condutividade termicamente ativada e permissividade marcada por dispersão a baixas frequências devido ao movimento de portadores de carga no material. A energia de ativação para os processos condutivos foi determinada a baixas frequências através da dependência da condutividade e do módulo elétrico com a temperatura. Em ambos os casos, observou-se um comportamento do tipo Arrhenius, com energias em torno de 0.7 eV. Valores semelhantes foram obtidas para os processos condutivos na região intra-grão, em altas frequências. Neste caso, as energias foram obtidas somente pela análise do módulo elétrico. O conjunto de resultados obtidos aponta para o sucesso da técnica para obter materiais de boa qualidade cristalográfica através de uma metologia simplificada e com custo reduzido. No caso específico do material em estudo no presente trabalho, esforços adicionais serão necessários para se obter cerâmicas com densidade relativa superior a 90 %.
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Santos, Denise de Jesus. "Produção e estudo dos defeitos de materiais fotossensíveis com estrutura cristalina do tipo silenita." Pós-Graduação em Física, 2014. https://ri.ufs.br/handle/riufs/5317.
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Photorefractive BTO presents useful properties for applications such as real-time holography, coherent light amplification and optical information processing, among others. The performance strongly depends on the defects induced by impurities, which can act as charge donors or acceptors. Defects can also be created by doping so that the properties can be adjusted to the desired application. Since ceramic reproduce well the single crystal properties and have advantages such as the simplicity and low cost of
processing, they become suitable for the study of the relationship between properties and defects in this material. The subject of this work was the production and characterization of bismuth titanate ceramics ( Bi12TiO20 - BTO) pure and doped with transition metals and rare earths. The study was focused on the point defects related to the site occupancy of the dopant in the BTO matrix, as well as on the valence of the dopant and possible charge compensation mechanisms associated with the defects. In this work, BTO ceramics were produced by solid state synthesis with calcination at 700º C/6h and sintering at 800º C/3h. The characterization techniques employed were Xray Diffraction (XRD), X-ray absorption spectroscopy (XAS), Scanning Electron Microscopy (SEM) and Impedance Spectroscopy (IS). Undoped and Dy , Er , Eu, Cr and Mn-doped BTO ceramic powders were produced, as well as ceramic bodies
undoped and doped with Dy, Cr and Mn. All samples presented single phase Bi12TiO20. The XAS analysis revealed the presence of T4+ and metallic Ti in BTO, a result that adds detail to the model for the formation of intrinsic defects in this material. Transition metals Cr and Mn presented oxidation states 6+ and 4+, respectively, when inserted into the BTO matrix, while the other elements present valence 3+. Concerning the site occupancy, it was determined that the Dy tends to occupy the Bi3+ site, while Er, Eu, Mn and Cr tend to occupy the Ti4+ site. Impedance measurements showed that none of
the doped samples had higher dark conductivity than pure sample. For the samples doped with Mn and Dy, which tend to occupy the Ti and Bi sites, respectively, the charge transport mechanisms are exactly the same as those verified in pure sample. For the Cr-doped sample, the Ti substitution occurs with a charge compensation mechanism that possibly give rise to new defects in the material.O BTO possui propriedades fotorrefrativas de interesse para aplicações como a holografia em tempo real, a amplificação de luz coerente e processamento de informação óptica, entre outras. O desempenho dos cristais fotorrefrativos depende fortemente dos defeitos criados por impurezas, os quais podem atuar como doadores ou aceitadores de carga. Os defeitos também podem ser inseridos por dopagem a fim de que as propriedades sejam adaptadas ao objetivo desejado. Uma vez que cerâmicas reproduzem bem as características do monocristal e apresentam vantagens de produção em relação aos materiais monocristalinos, como facilidade e baixo custo de processamento, elas se tornam adequadas ao estudo da relação entre defeitos e propriedades neste material. O objetivo deste trabalho foi a produção e caracterização de cerâmicas de Titanato de Bismuto (Bi12TiO20 - BTO) puro e dopado com metais de transição e terras raras, visando o estudo dos defeitos pontuais relacionados com e sitio de ocupação do dopante na matriz do BTO, valência do íon dopante incorporado na matriz cristalina e possíveis mecanismos de compensação de carga associados aos defeitos. Neste trabalho, cerâmicas de BTO foram produzidas por síntese de estado sólido, com calcinação a 700º C/6h, seguida de sinterização a 800º C/3h. Utilizamos como principais técnicas de caracterização a Difratometria de Raios X (DRX), Espectroscopia de Absorção de Raios X (XAS), Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Impedância (IS). Foram produzidos pós cerâmicos puros e dopados com Dy, Er, Eu, Cr e Mn e corpos cerâmicos de BTO puros e dopados com Dy, Cr e Mn. Todas as amostras apresentaram a fase Bi12TiO20. As análises de XAS mostraram a presença de Ti4+ e Ti metálico no BTO, resultado que acrescenta detalhes ao modelo de formação do defeito intrínseco neste material. Os metais de transição Cr e Mn apresentaram estados de oxidação 6+ e 4+, respectivamente, quando inseridos na matriz de BTO, enquanto os outros elementos apresentaram valência 3+. Em relação ao sítio ocupado pelos íons dopantes, determinou-se que o Dy tende a ocupar o sítio do Bi3+, enquanto o Er, Eu, Cr e Mn tendem a ocupar o sítio do Ti4+. As medidas de impedância mostraram que nenhuma das amostras dopadas apresentou maior condutividade no escuro do que a amostra pura. Nas amostras dopadas com Mn e Dy que ocupam o sitio do Ti e Bi, espectivamente os mecanismos de transporte de carga são exatamente iguais ao da amostra pura. Na amostra dopada com Cr, ao substituir o sitio do Ti ocorrem mecanismos de compensação de carga que dão origem a novos defeitos no material.
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Niu, Feng. "Development of novel catalysts for selective amination of alcohols." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R068.
Full textAbstract:
Les amines sont des intermédiaires très importants pour l’industrie chimique et la science de la vie, qui peuvent être synthétisés par différentes voies traditionnelles. L’amination catalytique d’alcools à base de métaux via le mécanisme dit “d'emprunt d'hydrogène” est un moyen relativement efficace et respectueux de l’environnement pour la synthèse de différentes amines primaires. Toutefois, certains problèmes subsistent, tels que le coût élevé des métaux nobles, la faible sélectivité en amines primaires, ainsi que la faible stabilité et la recyclabilité des catalyseurs. Pour résoudre ce problème, différentes stratégies ont été appliquées. Les dépôts de carbone produits lors du prétraitement des catalyseurs avec des alcools dans les conditions optimales ont été utilisés pour améliorer de manière importante la sélectivité de l’amination d’alcools en amines primaires (de 30-50 à 80-90%). Cette amélioration provient de l’empêchement stérique de l’hydrogénation des imines secondaires sur des nanoparticules de cobalt partiellement décorées au carbone. Une approche efficace pour protéger le catalyseur au cobalt de la désactivation par la promotion avec du bismuth liquide a été décrite pour l’amination sélective du 1-octanol. La N-alkylation d’amines par des alcools sur un catalyseur hétérogène, peu coûteux et efficace, à base d’hydroxyde de titane a également été proposée. Le catalyseur à faible acidité de Brönsted fournit une sélectivité supérieure à 90% en amines secondaires lors la réaction des alcools aromatiques et aliphatiques fonctionnalisés avec les aminesAmines are very important intermediates for chemical industry and life science, which can be synthesized through different traditional routes. Metals based catalytic amination of alcohols via the so-called “hydrogen borrowing” mechanism is a relative efficient and environmental benign way for synthesis of different primary amines. However, there are still some challenges exist, such as high cost of noble metals, low selectivity of primary amine products, and poor stability and recyclability for industrial applications. To solve these problems, different strategies have been applied in this thesis. Carbon deposition produced by catalyst pre-treatment with alcohols under the optimized conditions has been employed for major enhancement of the selectivity of alcohol amination to primary amines (from 30-50 to 80-90%), which arises from steric hindrance in hydrogenation of bulky secondary imines as intermediate products over partially carbon-decorated cobalt nanoparticles. An efficient approach to protect cobalt catalyst from catalytic deactivation by liquid bismuth promotion with different loading content was disclosed for selectively amination of 1-octanol. The N-alkylation of amines by alcohols over a cheap and efficient heterogeneous catalyst-titanium hydroxide was also proposed. The catalyst with mild Brönsted acidity provides the selectivity higher than 90% to secondary amines for functionalized aromatic and aliphatic alcohols and amines at high catalytic activity and stability
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Yu, Xiang. "Photocatalytic conversion of methane and reduction of CO2 with H2O." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R022/document.
Full textAbstract:
La photocatalyse est l'une des technologies clés pour les applications liées à l'énergie propre et à l'environnement. Le nombre d'applications basées sur la photocatalyse a considérablement augmenté au cours des deux dernières décennies.L'activation photocatalytique des liaisons C-H est un domaine émergent. Cependant, en raison de sa grande stabilité, une grande quantité d’énergie est habituellement consommée pour sa conversion, ce qui reste un problème à résoudre. La conversion du méthane et le mécanisme réactionnel qui se produisent sur les nanocomposites métal-hétéropolyacide-oxyde de titane ont été étudiés aux chapitres 3 et 4. L'oxydation du méthane est effectuée depuis plus d'un siècle. Étant donné que l'oxygène est une molécule très réactive, le méthane peut réagir très rapidement avec l'oxygène moléculaire en produisant le CO2. Par conséquent, il est difficile d'obtenir un produit souhaité avec un rendement élevé et une sélectivité importante. Nous avons observé l'oxydation photocatalytique directe et très sélective du méthane en monoxyde de carbone dans les conditions ambiantes. Les catalyseurs composites à base de zinc, d'acide tungstophosphorique et d'oxyde de titane présentent des performances exceptionnelles dans cette réaction, une sélectivité élevée en monoxyde de carbone et un rendement quantique de 7.1% à 362 nm. La réaction se réalise selon le mécanisme de type Mars-Van Krevelen et implique la formation de méthoxy-carbonates de surface en tant qu'intermédiaires et un cycle d'oxydation et de réduction du zinc. Au cours des dernières décennies, des recherches approfondies ont été dédiées à la conversion directe du méthane en alcools ou en hydrocarbures supérieurs. Bien que la conversion directe du méthane en produits à haute valeur ajoutée ait un potentiel environnemental et commercial important, il n’existe aucun procédé à l’échelle commerciale. Nous avons découvert une conversion photochimique directe quantitative hautement sélective (>90%) du méthane en éthane à température ambiante sur un nanocomposite argent-hétéropolyacide-oxyde de titane. Le rendement en éthane atteint 9% sur les matériaux optimisés. Une efficacité quantique élevée, une sélectivité élevée et un rendement significatif en éthane, associés à une excellente stabilité, sont les principaux avantages de la synthèse quantitative de méthane à partir de méthane en utilisant l'approche de boucle photochimique. L'augmentation du taux de dioxyde de carbone dans l’atmosphère et l'épuisement des réserves de combustibles fossiles ont suscité de vives inquiétudes quant à l'impact ultérieur sur le climat mondial et l'approvisionnement futur en énergie. Le chapitre 5 porte sur l’efficacité du nouveau catalyseur pour la conversion sélective de CO2 en CO. Les nanocomposites acide de phosphotungstique-oxyde de titane contenant du zinc ont présenté une activité exceptionnelle atteignant 50 µmol CO/g·h et une sélectivité (73%) dans la réduction photocatalytique du CO2 en CO en présence d'eau. Les expériences infrarouges in situ suggèrent que la réaction implique des bicarbonates de zinc contenant des groupes hydroxyle. La décomposition sous irradiation de ces espèces de bicarbonate de zinc conduit à la production sélective de monoxyde de carbone et d'oxygène. Lors des réactions photocatalytiques, la différence de morphologie du catalyseur a généralement un effet significatif sur les performances photocatalytiques. Le chapitre 6 a étudié l'effet des cristaux monocliniques de vanadate de bismuth (BiVO4) avec un rapport contrôlé de facettes {010} et {110} sur la réduction photocatalytique de CO2 par H2O. La réaction sous irradiation est considérablement améliorée par la photodéposition sélective de co-catalyseurs de Cu et Co sur différentes facettes, fournissant un flux de charge selon le Z-schémaPhotocatalysis is one of the key technologies for clean energy and environmental applications. The number of applications based on photocatalysis has increased dramatically for the past two decades. Photocatalytic activation of C-H bonds is an emerging field. Methane is a promising source of energy with a huge reserve and is considered to be one of the alternatives to non-renewable petroleum resources because it can be converted to valuable hydrocarbon feedstocks and hydrogen through appropriate reactions. However, due to its high stability, high energy is usually consumed for its conversion, which remains a problem to be solved. Methane conversion and reaction mechanism occurring on metal-heteropolyacid-titania nanocomposites were investigated in Chapters 3 and 4. Oxidation of methane has been carried out for more than a century. Since oxygen is a very reactive molecule, methane can react very rapidly with molecular oxygen and is prone to total oxidation till CO2. Therefore, it is difficult to obtain a desired product with high yield and high selectivity. We report here direct and selective photocatalytic highly-selective oxidation of methane to carbon monoxide under ambient conditions. The composite catalysts on the basis of zinc, tungstophosphoric acid and titania exhibit exceptional performance in this reaction, high carbon monoxide selectivity and quantum efficiency of 7.1% at 362 nm. The reaction is consistent with the Mars-Van Krevelen type sequence and involves formation of the surface methoxy-carbonates as intermediates and zinc oxidation-reduction cycling. In the past few decades, extensive research has focused on the direct conversion of methane to alcohols or higher hydrocarbons. The current processes of converting methane to alcohols or olefins are complex and expensive, because they require an intermediate step of reforming methane to syngas. Although the direct conversion of methane to more valuable products has significant environmental and potential commercial value, there is no commercial scale process available. We uncovered highly selective (>90%) quantitative photochemical direct conversion of methane to ethane at ambient temperature over silver-heteropolyacid-titania nanocomposites. The ethane yield from methane reaches 9 % on the optimized materials. High quantum efficiency, high selectivity and significant yield of ethane combined with excellent stability are major advantages of methane quantitative synthesis from methane using the photochemical looping approach. The rise in atmospheric carbon dioxide and the depletion of fossil fuel reserves have raised serious concerns about the subsequent impact of CO2 on the global climate and future energy supply. The use of abundant solar energy to convert carbon dioxide into fuel, such as carbon monoxide, methane or methanol, solves both problems simultaneously and provides a convenient method of energy storage. Chapter 5 addresses a new efficient catalyst for selective CO2 to CO conversion. The zinc containing phosphotungstic acid-titania nanocomposites exhibited exceptional high activity reaching 50 µmol CO/g·h and selectivity (73%) in the CO2 photocatalytic reduction to CO in the presence of water. The in-situ IR experiments suggest that reaction involves zinc bicarbonates containing hydroxyl groups. The decomposition of these zinc bicarbonate species under irradiation leads to the selective production of carbon monoxide and oxygen. In photocatalytic reactions, the difference in catalyst morphology usually has a significant effect on the photocatalytic performance. Chapter 6 studied the effect of monoclinic bismuth vanadate (BiVO4) crystals with controlled ratio of {010} and {110} facets for photocatalytic reduction of CO2 by H2O. The reaction under irradiation is significantly enhanced by selective photo-deposition of Cu and Co co-catalysts over different facets providing Z-scheme charge flow
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Jean, Florian. "Elaboration et caractérisation de couches minces et d'objets nanométriques de pérovskite sans plomb Na0,5Bi0,5TiO3." Limoges, 2013. https://aurore.unilim.fr/theses/nxfile/default/db1bf760-c4fb-4369-87a9-39d5b07e7dbb/blobholder:0/2013LIMO4053.pdf.
Full textAbstract:
Ce travail est consacré à la synthèse et la caractérisation du matériau sans plomb Na0,5Bi0,5TiO3 (NBT) par différentes techniques, sous formes de films minces et de nano-objets supportés ou non. Dans un premier temps, des films minces de NBT ont été déposés par ablation laser pulsée sur différents substrats monocristallins de nature oxyde avec pour but l’obtention d’une croissance épitaxiale. L’effet de l’insertion d’une couche tampon de CeO2 sur la croissance des films a été étudié. Les propriétés électriques (ferroélectriques, diélectriques, agilité dans le domaine des micro-ondes) ont été mesurées sur des films minces de NBT épitaxiés, dopés ou non par le manganèse, et déposés sur substrats de LaAlO3 nus et SrTiO3 recouverts d’une électrode oxyde de LaNiO3. Dans un deuxième temps, des nano-objets de NBT ont été élaborés par différentes voies chimiques. Les voies de synthèses sol-gel, hydrothermale et hybrides ont permis l’obtention de la phase pérovskite de NBT. Pour chaque voie de synthèse, différents paramètres influençant la structure ou la forme des nano-objets ont été étudiés. Une voie physique, l’ablation laser en milieu liquide, a également été explorée. Enfin, des nano-objets de NBT ont été déposés par ablation laser pulsée et par dépôt chimique en solution sur des substrats monocristallins recouverts ou non d’une électrode de platine. L’utilisation de substrats de saphir-c vicinaux nus combinée à un dépôt par voie physique permet l’auto-arrangement des objets à la surface du substrat. Les propriétés électriques locales ont été mesurées par PFM pour des grains isolés mettant en avant le caractère polaire de ces derniersThe present work is devoted to the synthesis and the characterization of the lead-free Na0. 5Bi0. 5TiO3 (NBT) material by different techniques in the form of thin films and nano-objects supported or not. In a first step, NBT thin films were elaborated by pulsed laser deposition on different single crystal oxide substrates in order to reach the epitaxial growth. The effect of the insertion of a CeO2 buffer layer on the growth of the films was studied. The electrical properties (ferroelectric, dielectric, tunability in the microwave regime) were measured on epitaxial NBT thin films doped or not and deposited on LaAlO3 bare substrate and SrTiO3 substrate coated with an oxide electrode of LaNiO3. In a second step, NBT nano-objects were elaborated by different chemical routes. The sol-gel, hydrothermal and hybrid synthesis allowed the formation of the perovskite phase of NBT. For each route, different parameters influencing the structure or the form of the nano-objects were studied. A physical route, the laser ablation in a liquid media, has also been explored. Finally, NBT nano-objects were fabricated by pulsed laser deposition and by chemical solution deposition on single crystal substrates coated or not with a platinum electrode. The use of bare vicinal c-sapphire substrates combined with the physical route allows the self-organization of the objects at the surface of the substrate. The local electrical properties were measured by PFM for isolated grains, highlighting their polar nature
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Nader, Adel. "Supraconductivité des composés lamellaires incommensurables." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0013.
Full textAbstract:
Les composes lamellaires incommensurables sont construits par l'alternance d'une ou deux couches imxi et d'un, deux ou trois feuillets itx#2i ou m : pb, sn, bi, sb ou terre rare, t : nb, ta, ti, v et x : s ou se. La commensurablite entre les deux sous structures des deux types couches est parfaite selon les axes b et c, or selon l'axe a les parametres de maille ont un rapport qui s'approche de 3 d'ou le nom incommensurables. Certains de ces composes sont supraconducteurs avec des temperatures critiques entre 0,4 k et 5,5 k. Nous avons etudie le comportement du champ magnetique critique de ces composes par des mesures de magnetoresistance entre t#c et 0,05 k et d'apres cette etude on peut les classer en trois groupes : 1) les composes a base de plomb ou d'etain se comportent comme des intercalaires des composes peres nbs#2 et nbse#2 avec une anisotropie qui augmente au fur et a mesure que les plans supraconducteurs sont eloignes. 2) les composes a base de bismuth ont une anisotropie plus faible que les composes peres nbs#2 et nbse#2 3) les composes a base de la qui sont (lase)#1#,#1#4(nbse#2)#m (m : 1 ou 2) ont une anisotropie tres forte de l'ordre de 30 et un champ critique resistif de courbure positive qui diverge a basse temperature, comme dans les supraconducteurs de haute temperature critique. Ce comportement est, probablement, du a des fortes fluctations thermiques qui causent la fusion du solide de vortex en un liquide de vortex. Le champ critique h#c#2 calcule par la loi d'echelle d'ullah et dorsay montre plutot un cmportement lineaire et une saturation a basse temperature. Un diagramme de phase a ete propose pour ces deux composes.
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Kundu, Animesh. "Hydrothermal synthesis of sodium bismuth titanate and titanate nanofibers." 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3341187.
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Wang, Yi-Chi, and 王藝琦. "Bismuth Titanate Compound: Synthesis, Characterization and Photocatalytic Applications." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/38177409062803661059.
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碩士國立中興大學
化學工程學系所
104
The preparetion of photocatalyst Bismuth Titanate compound has been synthesized by the combination of direct hydrolysis method and hydrothermal treatment. The investigated parameters include molar ratio of Bi:Ti, hydrothermal temperature, and hydrothermal time. The photocatalytic reaction efficiency and the adsorption of dark box were used to determine the best conditions for the preparation of bismuth titanate photocatalyst. The structural information and morphology of the nanoparticles Bismuth Titanate compound were characterized by BET、XRD、TGA、FTIR、SEM/TEM、EDS、ICP、ESCA and UV-visble spectroscopy. In this study, the bismuth titanate photocatalyst was investigated by the photodegradation of methyl orange under the irradiation of UV light, and no light adsorption experiments (dark box adsorption). The degradation results of the methyl orange and dark box adsorption indicate that the best conditions of the preparation of bismuth titanate are the Bi : Ti molar ratio of 1:1, the hydrothermal temperature of 200°C, and the hydrothermal time for 12h, and can reach the best photocatalytic activity and the degradation rate of 48 %.
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Lu, Yen-Ting, and 呂燕婷. "Synthesis and electrical properties of sol-gel bismuth titanate." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/56306353725852980205.
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碩士國立臺灣大學
材料科學與工程學研究所
87
We have synthesized sol-gel bismuth titanate. Bismuth methoxyethoxide and titanium methoxyethoxide precursors were used. They were mixed by a molar ratio of 1.23:1 (Ti:Bi), and followed by a hydrolysis process ( [H2O]=1.135M, [H2O]/[M(OR)n]=1.305M ) to prepare bismuth titanium oxide powder. The Bi2Ti2O7 (B2T2) phase appeared when the powder was calcined at 550oC. That phase remained stable at 700oC/2hr. At the higher temperature, the B2T2 phase was transformed into Bi4Ti3O12 (B4T3) and Bi2Ti4O11(B2T4) phases. When the green body was sintered at 1150oC/90min, a mixed phase of B4T3 and B2T4 were obtained. They showed a remanent polarization of 3.77mC/cm2, and coercive force of 24kV/cm, a dielectric constant of 101.3(1MHz) and a loss tangent of 0.0193(1MHz). When the green body was sintered at 1200oC/45min, it exhibited B2T2 phase without ferroelectricity. Sol-Gel derived bismuth titanates in our system has shown better dielectric and ferroelectric properties than the other methods reported in the literature. They have potential to be applied to transistors, capacitors, and nonvolatile memory devices, etc.
46
Jackson, Dennis L. "An Ising-like model to predict dielectric properties of the relaxor ferroelectric solid solution BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃." Thesis, 2011. http://hdl.handle.net/1957/26334.
Full textAbstract:
We developed a model to investigate the dielectric properties of the
BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods
to determine all polarization states for every atomic configuration of 2 x 2 x 2
supercells of BT-BZT. Each supercell is placed on a lattice with an Ising-like
interaction between neighboring cell polarizations. This method allows us to
consider long range disorder, which is not possible with ab initio methods
alone, and is required to properly understand relaxor ferroelectric materials.
We analyze the Monte Carlo data for a single lattice configuration using the
multiple histogram method, and develop a modified histogram technique to
combine data from multiple lattice configurations. Our calculated values of
dielectric constant, specific heat, and polarization agree reasonably well with
experiment.Graduation date: 2012
47
Steiner, Sebastian. "Defect Chemistry of Sodium Bismuth Titanate and its Solid Solutions." Phd thesis, 2020. https://tuprints.ulb.tu-darmstadt.de/11552/8/Defect%20Chemistry%20of%20Sodium%20Bismuth%20Titanate%20and%20its%20Solid%20Solutions_Thesis%20Sebastian%20Steiner.pdf.
Full textAbstract:
In this work, the perovskite structured system Na0.5Bi0.5TiO3 (NBT) and its solid solutions (1-x)(Na0.5Bi0.5TiO3)-xBaTiO3 (NBT-BT), (1-x)(Na0.5Bi0.5TiO3)-xSrTiO3 (NBT-ST) and [(1-x)(1-y)(Na0.5Bi0.5TiO3)-yBaTiO3)]-xCaZrO3 (NBT-BT-CZ) have been investigated. In detail, the impact of A-site non-stoichiometry and B-site doping on the electrical, dielectric, ferroelectric and piezoelectric properties was discussed. The main aim was to reveal the defect chemical origin of extremely high oxygen ionic conductivity in NBT and to apply the gained knowledge to control and enhance the properties of NBT-based solid solutions. This could result in a large application range of NBT and its solid solutions from excellent solid ionic conductors to high-temperature dielectric materials.
High levels of oxygen ionic conductivity were rather unexpected in NBT and highlight that the already established defect chemical models for lead- or barium-based systems do not hold for this system. It was assumed that defect complexes form in NBT between a B-site defect and a generated oxygen vacancy, resulting in a non-linear increase of the effective oxygen vacancy concentration.
By performing temperature dependent impedance spectroscopy, the electrical properties of NBT have been investigated in more detail. With the help of density functional theory (DFT) calculations, an analytical model was established with regards to a possible defect complex formation in acceptor doped NBT. Further, the conducted work delivers proof that the association energy of the defect complex is dependent on the doping element (in particular mechanical contributions from the differing ionic radii, Coulomb interactions with concerning the valence state and covalent contributions), doping concentration and crystal phase. With a precise adjustment of the A-site and B-site defect chemistry, controllability of the ionic conductivity in NBT could be reached in such a way, that either high ionic conducting NBT or low, semiconducting NBT can be processed.
Based on the gained knowledge, the solid solution NBT-6BT was investigated for A-site non-stoichiometry and B-site acceptor doping to reveal similar defect chemical mechanisms as observed in NBT. B-site acceptor doping leads to similar electrical properties. The induction of high levels of oxygen ionic conductivity is, therefore, following the same mechanism in NBT-6BT. Based on this finding, acceptor doping was revealed to be not a valid approach to enhance the ferroelectric properties in NBT and NBT-based solid solutions. A-site non-stoichiometry featured a significant impact on the non-ergodic/ergodic relaxor transition on NBT-6BT which led to considerably different ferroelectric and piezoelectric properties at room temperature. Additionally, the presence of increased oxygen vacancy concentration is directly related to chemical diffusion during the processing.
This circumstance was utilized in the core-shell structured NBT-based solid solution NBT-25ST. In detail, B-site doping and A-site non-stoichiometry were simultaneously applied on NBxT-25ST to elucidate the origin of forming this particular chemical inhomogeneity which could either be facilitated by the occurrence of A-site vacancies or oxygen vacancies. With the help of a detailed SEM analysis, it could be confirmed that the oxygen vacancy concentration is mainly responsible for the formation of core-shell structures. Low oxygen vacancy concentration stabilized fine-grained, core-shell structures, larger concentrations result in grain growth and homogeneous elemental distribution. A remarkable impact on the resulting piezo- and ferroelectric properties could be revealed. As the NBT-rich core was attributed to being responsible for non-ergodic relaxor behavior, a core-shell structured composition should provide non-ergodic behavior. This assumption holds for A-site non-stoichiometry in NBxT-25ST. Acceptor doping with Fe (high vacancy concentration), however, leads to non-ergodic relaxor behavior, Nb-donor doping (low vacancy concentration results in ergodic relaxor behavior at room temperature irrespective on additional A-site non-stoichiometry. This result confirms that, besides changing the occurrence of core-shell microstructures, the ferro- and piezoelectric responses of the NBT-rich cores themselves are affected by the doping. This results in ergodic behavior in the case of Nb-donor doping.
The feature of relaxor behavior was utilized to further enhance the application range of NBT. Therefore, the solid solution NBxT-6BT-yCZ was investigated for its temperature-dependent dielectric properties. It could be confirmed that the stoichiometric NBT-6BT-20CZ composition exhibits an exceptionally large application temperature range where the criterion of temperature stable permittivity and low dielectric loss are fulfilled simultaneously. The almost temperature-independent permittivity was attributed to the presence and coexistence of two different kinds of polar nano regions, in the respective low temperature (LT) and high temperature (HT) form. The dielectric losses, however, limited the application range. By the addition of BiAlO3 (BA), a further decrease of the dielectric losses could be achieved. This resulted in an excellent high-temperature dielectric material that can by far outperform commonly used high-temperature capacitors for the given operation temperature window in which the permittivity and loss criterion are fulfilled simultaneously.
The here presented results elucidate the defect chemical origin of oxygen ionic conductivity in NBT. By applying the gained defect chemical knowledge, oxygen vacancy formation can precisely be controlled and the application range of NBT and its solid solutions could be enlarged towards tunable piezo- and ferroelectric properties as well as excellent temperature stable dielectric properties.
48
Liao, Ying-Hsiu, and 廖英秀. "Synthesis, Characterization and Photocatalytic Applications of Ag-Modified on Bismuth Titanate." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/90497911825204078035.
Full textAbstract:
碩士國立中興大學
化學工程學系所
105
Nano-photocatalyst Bi4Ti3O12 were successfully synthesized via hydrothermal treatment method using bismuth nitrate and tetrabutyl titanate as precursors. The investigated parameter included different hydrothermal treatment time. The photocatalytic reaction efficiency and the adsorption of dark box were used to determine the best conditions for the preparation of bismuth titanate photocatalyst. The crystal structure, bond strength and surface morphology of nanometer photocatalyst were analyzed by BET, XRD, FTIR, SEM, TEM, EDS, ESCA and UV-visible spectrum. In the second part, sliver nitride is added into the photocatalyst by the precipitation method. The synthesized photocatalyst of Ag/Bi4Ti3O12 reveals the good responsive ability to visible light. The optimal synthesized parameters of catalyst in the process have been determined. The optimal amount of silver nitride is 3wt%, and the best calcined temperature is 300℃. The degradation of methyl orange can reach 95% was twice higher than the pure Bi4Ti3O12 under the visible light irradiation for 6 h.
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Chiang, Kuo-Chang, and 蔣國璋. "The study of the indium-containing bismuth titanate ceramics and thin films." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/41659741431125759721.
Full textAbstract:
碩士國立東華大學
材料科學與工程學系
94
This experiment is to investigate the indium-doped Bi4Ti3O12 (BTO) and (Bi,Nd)4Ti3O12 (BNT) ceramics, and the ferroelectricity of indium-modified Bi4Ti3O12 thin films. This research was divided into two parts. The first one was the Indium-doped BTO and BNT ceramics prepared by solid-state reaction. The structure, phase components, and microstructure of BTO and BNT changed with the incorporation of indium between the Bi site and Ti site. The chemical formulation for In-BTO is [(Bi3.6+xIn0.4-x)(Ti3-xInx)Oy] with x=0, 0.1, 0.2, and 0.3, while it is [(Bi3.15+xNd0.4In0.4-x)(Ti3-xInx)Oy] with x=0, 0.1, 0.2, and 0.3 for In-BNT. In the second part, the experiment was to investigate the indium-modified Bi4Ti3O12 (BTO) ferroelectric thin films prepared by radio-frequency magnetron sputtering. We firstly studied the effect of the variation of indium component on the ferroelectricity of indium-doped Bi4Ti3O12 thin films produced with target compositions of [Bi2.45In0.35+xTi2.9Oz] at x = 0, 0.1, and 0.2. After the best performance were displayed by the target with x= 0.2, the effect of the variation of bismuth content on the ferroelectricity of indium-doped Bi4Ti3O12 thin films was studied by using the targets with the composition of [Bi2.45+yIn0.55Ti2.9Oz] at y=-0.1, 0, and 0.1. The experimental results for the In-BTO and In-BNT ceramics showed that the Bi-less Bi2Ti2O7 phase disappeared and layered perovskite Bi4Ti3O12 phase became the major phase as the formulated In content increased at the B or Ti site or as the x value increased. With the increasing of the indium content or the higher x value, the In-BTO and In-BNT grains were gradually changed from the small granules to the slab with a flat shape. According to the results of EDS analysis, the incorporation of indium almost existed in Bi2Ti2O7 phase instead of Bi4Ti3O12. If the amount of incorporating indium was large, the solid solution of the In2O3 phase with some Bi and Ti appeared. The experimental results of indium-added Bi4Ti3O12 thin films showed that the annealing temperature for the sputter-prepared indium-doped thin films was 50oC higher than those produced by the sol-gel method. The films with the best ferroelectric results were prepared by the target with a composition at x=0.2 or the formulated Bi2.45In0.55Ti2.9O11.3 target. After annealed at 650oC for 10 min in air, these films performed best and had the remanent polarization and coercive field of 7.3 µC/cm2 and 208.7 kV/cm, respectively. However the experimental results of indium-doped BTO thin films were not as expected as those films prepared by the chemical solution route. These sputtered indium-added films displayed a degraded fatigue resistance, which could be attributed to the deviations in the film composition. Further improvements in the preparation of the In-added Bi4Ti3O12 films are necessary.
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Yeh, Teng-Hao, and 葉騰豪. "Fabrication and characterization of Neodymium-substituted Bismuth Titanate/Al2O3 for MFIS-FET." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/25605292807706873049.
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