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Journal articles on the topic "CaCu3Ti4O12"
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Konchus, Boris, Oleg Yanchevskiy, Anatolii Belous, and Oleg V'yunov. "SYNTHESIS, PROPERTIES CaCu3Ti4O12 WITH COLOSSAL VALUE OF THE DIELECTRIC PERMITTIVITY." Ukrainian Chemistry Journal 85, no. 6 (July 31, 2019): 77–86. http://dx.doi.org/10.33609/0041-6045.85.6.2019.77-86.
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Ceramic materials CaCu3Ti4O12 were synthesized by solid-phase reactions technique. The sequence of chemical reactions during the synthesis has been determined. Phase CaCu3Ti4O12 appears at 700 °C. At 800 – 900 °C, the intermediate phases CaTiO3, CuTiO3 and Ca3Ti2O7 are formed. Calcium and copper titanates, CaTiO3 and CuTiO3 interact to form CaCu3Ti4O12. Ca3Ti2O7 phase with pyrochlore structure is stable and prevent the formation of final product, CaCu3Ti4O12. A method for the synthesis of CaCu3Ti4O12 by solid-state reactions technique from previously synthesized CaTiO3 (at 1050 °С) and CuTiO3 (at 950 °С), taken in a molar ratio of 1:3, is proposed. This method give the possibility to avoid the appearance of an undesirable Ca3Ti2O7 phase with the pyrochlore structure and to reduce the content of free copper oxide to value less than 0.5 mol.%. In addition, instead of the copper oxide, which is usually used in solid-state reaction technique, the chemically more active form of the copper-containing reagent, CuCO3∙Cu(OН)2 were used. This reduce the synthesis time of the intermediate CuTiO3. The crystal structure, chemical composition, microstructure and electrophysical parameters of ceramics have been analyzed. The synthesized ceramics CaCu3Ti4O12 is cubic body-centered (space group Im-3) with the unit cell parameter a = 7.3932 Å, which agreed with the literature data. The calculated tolerance factor of CaCu3Ti4O12, t = 0.7626 is not sufficient for a stabilization of peroskite ABO3 structure; that is why the crystal structure of this compound contains 3 different cation sites: dodecahedral (Ca2+), octahedral (Ti4+), tetrahedral (Cu2+). At 1150 °C, the density of CaCu3Ti4O12 ceramic sintered has a maximum (90% of the theoretical density). At infra-low frequencies (10-3 Hz), the dielectric constant (e) reaches record values of 107, however, dielectric losses (tg d) up to 10 were observed. In the frequency range 10-3 - 105 Hz the value of ɛ exceeds 104; and at 105 Hz minimum of the dielectric losses (tg δ ~ 0.1) is observed. A comparative analysis of methods for the synthesis of CaCu3Ti4O12 shows that the synthesis conditions of material of the same chemical composition can be crucial in creating high dense ceramic with uniform grains, high dielectric constant and low dielectric losses in a wide frequency range.
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Masingboon, C., P. Thongbai, and S. Maensiri. "Giant Dielectric Response in Perovskite-Derivative CaCu3Ti4O12 Prepared by Polymerized Complex Method." Advances in Science and Technology 45 (October 2006): 2345–50. http://dx.doi.org/10.4028/www.scientific.net/ast.45.2345.
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Nano-sized powders of CaCu3Ti4O12 (crystallite size of 44, 58 and 71 nm) have been synthesized by a polymerized complex method, followed by calcination the synthesized precursor at 600, 700 and 800°C in air for 8h. The CaCu3Ti4O12 powders were then characterized by XRD, FTIR and SEM. Sintering of the powders was conducted in air at 1100°C for 16h. The XRD results confirmed a typical perovskite CaCu3Ti4O12 structure in all the sintered ceramics, although the presence of a second phase of CaTiO3 was observed in the sample sintered using the powders calcined at 600°C. Microstructure of the sintered CaCu3Ti4O12 ceramics was observed by SEM and the grain size of the materials evaluated with polished using the line intercept method were found to be ~ 10-20 μm. A giant frequency-dependent dielectric constant samples (ε ~10000-60000) with weakly temperature dependence and was observed in the all the samples. The highest dielectric constant of the material was found to be ~60000 (at 140-160°C, 100 Hz) in the sample sintered using the powders calcined at 700°C. The origin of the high permittivity observed in these CaCu3Ti4O12 ceramics is attributed to the Maxwell-Wagner polarization mechanism.
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Kurniawan, Widodo Budi. "PENGUKURAN NILAI DIELEKTRIK MATERIAL CALCIUM COPPER TITANAT ( CaCu3Ti4O12) MENGGUNAKAN SPEKTROSKOPI IMPEDANSI TERKOMPUTERISASI." Jurnal Sains Dasar 6, no. 1 (May 22, 2017): 26. http://dx.doi.org/10.21831/jsd.v6i1.13565.
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Telah dilakukan pengukuran tetapan dielektrik kompleks dan besarnya impedansi kapasitor pada material keramik Calcium Copper Titanate dengan struktur material CaCu3Ti4O12 (CCTO) dengan kemurnian 99 % menggunakan metode spektroskopi impedansi terkomputerisasi dalam rentang frekuensi 5 kHz – 120 kHz. Tetapan dielektrik maksimum terukur pada sampel yang disintering dengan suhu 7000C yaitu 745 pada frekuensi 5 kHz dan besarnya impedansi kapasitor maksimum terjadi pada sampel CCTO non sintering yaitu 150434 Ω. Hasil penelitian menunjukkan adanya pengaruh frekuensi terhadap tetapan dielektrik kompleks dan impedansi kapasitor dari material yang diteliti. Kata kunci : spektroskopi impedansi, CaCu3Ti4O12, tetapan dielektrik kompleks dan impedansi kapasitor. MEASUREMENT OF THE DIELECTRIC CONSTANT CALCIUM COPPER TITANATE (CaCu3Ti4O12) MATERIALS USING COMPUTERIZED IMPEDANCE SPECTROSCOPY ABSTRACT The measurement of the complex dielectric constant and the magnitude of the capacitor impedances of the ceramic materials Calcium Copper Titanate CaCu3Ti4O12 (CCTO) with purity of 99% has been done by using the method of computerized impedance spectroscopy in the frequency range 5 kHz - 120 kHz. The highest dielectric constant of the material was found to be 745 at 5 kHz in the sample sintered 7000C and the highest impedance of capacitor occured in CCTO sample non sintered that is 150434Ω. The results showed that complex dielectric constant and impedance of the capacitor of the material under study was frequency dependent. Keywords : impedance spectroscopy, CaCu3Ti4O12,complex dielectric constant and impedance of capacitor
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Ramírez, M. A., R. Parra, M. M. Reboredo, J. A. Varela, M. S. Castro, and L. Ramajo. "Elastic modulus and hardness of CaTiO3, CaCu3Ti4O12 and CaTiO3/CaCu3Ti4O12 mixture." Materials Letters 64, no. 10 (May 2010): 1226–28. http://dx.doi.org/10.1016/j.matlet.2010.02.058.
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Zhang, Yun Qiang, Li Qiu Su, Xiao Fei Wang, Hui Xian Wang, and Li Ben Li. "Study on the Dielectric Properties of CaCu3Ti4O12 Ceramics by the Brickwork Layer Model." Advanced Materials Research 418-420 (December 2011): 1056–59. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.1056.
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A brickwork layer model was used to investigate the dielectric properties of CaCu3Ti4O12 ceramics. It is equivalent to Debye model under the Maxwell- Wagner-type mechanism. Arrhenius relation could be obtained by the assumption that the grains in the CaCu3Ti4O12 ceramic are of semiconductivity. The dependence of the dielectric constant on the grain size and temperature were well fitted by the model.
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You, Jing Han, Qing Dong Chen, Wei Wei Ju, Li Ben Li, and Kai Chen. "Effects of the Replacement of Ti by Zr on the Dielectric Properties of CaCu3Ti4012 Ceramics." Key Engineering Materials 368-372 (February 2008): 118–20. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.118.
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CaCu3Ti4O12 and CaCu3Ti3.9Zr0.1O12 ceramics were prepared by the traditional solid-state reaction method and the dielectric properties were investigated. Comparison of the results of the two samples examined indicated that the partial replacement of titanium by zirconium in the system CaCu3Ti4O12 may result in different changes of the dielectric constant and dielectric loss. For these experimental phenomena possible explanations and predictions also have been presented.
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Fang, Liang, Mingrong Shen, Jing Yang, and Zhenya Li. "Reduced dielectric loss and leakage current in CaCu3Ti4O12/SiO2/CaCu3Ti4O12 multilayered films." Solid State Communications 137, no. 7 (February 2006): 381–86. http://dx.doi.org/10.1016/j.ssc.2005.12.004.
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Qin, Dake, Guozheng Liang, and Aijuan Gu. "CaCu3Ti4O12 electrospun fibre: A new form of CaCu3Ti4O12 and its dielectric property." Journal of Alloys and Compounds 549 (February 2013): 11–17. http://dx.doi.org/10.1016/j.jallcom.2012.09.083.
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You, Jing Han, Xiao Yang Gong, Tong Wei Li, Qing Dong Chen, and Li Ben Li. "Dielectric Properties of CaCu3Ti4O12 Ceramics." Key Engineering Materials 434-435 (March 2010): 253–55. http://dx.doi.org/10.4028/www.scientific.net/kem.434-435.253.
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CaCu3Ti4O12 ceramics were prepared by the traditional solid-state reaction method and the dielectric properties were investigated, the activation energy and relaxation time factor of the samples were calculated. Debye relaxation theory was attempted to analyze the experimental datum, the static and high-frequency dielectric constants were obtained according to Cole-Cole spectra. The temperature dependence of the dielectric constant of CaCu3Ti4O12 were fitted by computer and the theoretical results nearly agree with experimental results.
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Luo, Feng Chao, Jin Liang He, Jun Hu, and Yuan Hua Lin. "Influence of Slight Bismuth Additive on the Properties of Calcium Copper Titanate Ceramic." Advanced Materials Research 105-106 (April 2010): 274–77. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.274.
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The CaCu3Ti4O12 samples with slight amount of doped bismuth were prepared and tested in this research. No second phase with bismuth was found in the doped samples. It was inferred that the bismuth ions has entered the lattice and take the place of the calcium ions. The grain size was diminished with the increase of the bismuth content. The bismuth atoms can inhibit the grains from growing large, and it could be used to modify the microstructure of CaCu3Ti4O12 ceramic. The reduction of the grain size resulted in the decrease of the relative dielectric constant, according to the “internal barrier layer capacitance (IBLC)” theory. The impedance measurements showed that the doped samples have less conductivity and lower potential barrier at the grain boundaries, and the substitution of the bismuth ions on the calcium cites might be the reason for it. As a result of the lowered potential barrier, the non-ohmic I-V property of the CaCu3Ti4O12 ceramic almost disappears in the doped ones.
Dissertations / Theses on the topic "CaCu3Ti4O12"
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Costa, Sara Isabel Rodrigues. "Ceramic processing and microstructure/property relation in CaCu3Ti4O12." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11735.
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Mestrado em Ciência e Engenharia de MateriaisCaCu3Ti4O12 (CCTO) foi produzido a temperatura baixa por moagem de alta energia e o seu impacto nas propriedades eléctricas estudado. O CCTO desenvolve um mecanismo de condensador de interface interna resistiva (do inglês IBLC) devido a desvios de estequiometria da composição inicial, a temperaturas de processamento intermédias (900-1100 oC). Este projeto tem como objectivo diminuir a temperatura de calcinação e, consequentemente, a de sinterização, de forma a reter a composição estequiométrica durante o processamento do CCTO. A evolução da fase CCTO foi controlada por difração de raios-X e as amostras foram sinterizadas pelo método convencional no intervalo de temperaturas entre 700 e 1100 oC, e caraterizadas por espetroscopia de impedância em temperaturas criogénicas e acima de temperatura ambiente. As amostras sinterizadas a 1100 oC foram, em seguida, caraterizadas por SEM e EDS. Os resultados mostram que a técnica de moagem de alta energia permite produzir pós de CCTO a temperaturas mais baixas, 700 oC, quando comparada com a síntese convencional por reação no estado sólido (950.-.1100 oC). As medidas por espetroscopia de impedância mostram que as amostras sinterizadas a 700 oC são constituídas por grãos resistivos com resistividade > 1 MΩ cm a 523 K e, portanto, a composição estequiométrica permanece inalterada e o mecanismo de IBLC não está presente. A densidade relativa é, contudo, bastante baixa, 57 %. Com o aumento da temperatura de sinterização, os grãos começam a tornar-se semicondutores e o mecanismo IBLC começa a desenvolver-se, acompanhado por um decréscimo acentuado da resistividade do grão em pelo menos seis ordens de grandeza. Para temperaturas de sinterização intermédias, 800.-.900 oC, os grãos são constituídos por uma fase semicondutora rodeada por uma fase resistiva. Para temperaturas de sinterização de 1000 oC, os grãos são semicondutores com resistividade ~ 40 Ω cm e fronteiras de grão ~ 530 Ω cm a 523 K. As amostras sinterizadas a 1100 oC são constituídas por grãos semicondutores e fronteiras de grão resistivos com resistividade ~ 65 kΩ cm a 523 K. Esta diferença de resistividades parece estar na origem da elevada permitividade dielétrica no intervalo de radiofrequências. A análise por EDS revela que a amostra sinterizada a 1100 oC é deficiente em cobre, o que contribui para o aumento da condutividade do grão. A transformação do grão resistivo em semicondutor parece estar, portanto, associada à difusão e eventual volatilização de cobre a temperaturas de processamento elevadas
CaCu3Ti4O12 (CCTO) powders were produced at low temperatures by high-energy ball milling and its impact on the electrical properties of CCTO ceramics carried out. CCTO ceramics develop an internal barrier layer capacitance (IBLC) mechanism due to small changes in stoichiometry, which seems to start at intermediate processing temperatures (900.-.1100.oC). This project aims to decrease the calcination and sintering temperatures to retain the stoichiometric composition during processing of CCTO ceramics. The evolution of the CCTO phase was evaluated by X-ray diffraction and ceramics were prepared by conventional sintering at temperatures between 700 and 1100 oC. The samples were characterised by impedance spectroscopy at subambient and high temperatures. Ceramics sintered at 1100 oC were characterised by SEM and EDS. The results show that high-energy ball milling permits the production of CCTO powder at lower temperature, 700.oC, compared to conventional solid state reaction (950.-.1100.oC). Impedance spectroscopy measurements show that ceramics sintered at a temperature of 700.oC, the stoichiometric composition of CCTO is retained and consists of insulating grains with a resistivity > 1 MΩ cm at 523 K. The relative density is, however, rather low, 57 %, and the IBLC mechanism is not present in this sample as usually observed for CCTO ceramics. When the sintering temperature increases, the insulating grains start to transform into semiconducting and the IBLC mechanism starts to appear, accompanied by a significant drop on the resistivity by at least six orders of magnitude for ceramics sintered at 1000 oC. At intermediate sintering temperatures, 800 - 900.oC, the grains are electrically heterogeneous containing both insulating and semiconducting phases. When samples are sintered at 1000 oC, the grains are totally semiconducting with resistivity of ~ 40 Ω cm and grain boundary resistivity of ~ 530.Ω.cm at 523 K. Ceramics sintered at 1100 oC exhibit semiconducting grains surrounded by insulating grain boundary with resistivity of ~ 65 kΩ cm at 523 K, and this seems to be responsible for the high effective permittivity at radio frequencies for dense ceramics. The EDS analysis shows CCTO ceramics sintered at 1100 oC to be Cu-deficient and it contributes to the increase of the bulk conductivity. The transformation of the resistive into semiconducting grains and the evolution of the IBLC mechanism may be, therefore, linked to the diffusion and eventual volatilisation of copper at elevated processing temperatures.
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Porfirio, Tatiane Cristina. "Preparação e caracterização microestrutural e dielétrica da perovsquita CaCu3Ti4O12." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-17092015-090949/.
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Neste trabalho pós de CaCu3Ti4O12 foram preparados por reação em estado sólido e por técnicas de solução: complexação de cátions e coprecipitação dos oxalatos. Foram realizados estudos de formação de fase, densificação e propriedades dielétricas das cerâmicas sinterizadas. Para efeito comparativo, ta is propriedades foram determinadas em amostras puras e contendo dissilicato de lítio (LSO) e fluoreto de lítio (LiF) como aditivos de sinterização. O principal objetivo foi verificar o efeito do uso dos diferentes aditivos de sinterização na microestrutura, densificação e propriedades dielétricas do CCTO. Os principais resultados revelaram que pós preparados por técnicas de solução apresentam fase única após calcinação em condições selecionadas. Foi verificado que os aditivos influenciam na densificação, possibilitando obter cerâmicas com 95% da densidade teórica do CCTO a 1025°C. As amostras preparadas por diferentes técnicas apresentam propriedades similares, com exceção das características microestruturais. A permissividade elétrica determinada à temperatura ambiente é da ordem de 104 independentemente do método de síntese. As menores perdas dielétricas foram obtidas para amostras contendo LiF como aditivo de sinterização.In this work the effects of the method of synthesis and sintering additives on the microstructure and dielectric properties of CCTO were investigated. Powder mixtures were prepared by the cation complexation and coprecipitation methods, and by mixing of the starting oxides, for comparison purposes. Lithium dissilicate (LSO) and lithium fluoride (LiF) were used as sintering aids. The main results revealed that powders prepared by solution techniques have single phase after calcination at selected conditions. The additives were found to influence the densification allowing for obtaining high relative density (≥ 95%) at 1025ºC. Specimens prepared by different methods show similar properties except on microstructure features. The electric permittivity is of the order of 104 for all investigated specimens independent on the method of synthesis. The dielectric loss is found to be lower for specimens prepared with LiF as sintering aid.
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Kawrani, Sara. "Synthesis, Characterizations and applications of oxides materials based on CaCu3Ti4O12." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS085.
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Les oxydes de type pérovskites présentent différentes propriétés selon leur structure et leur composition chimique. Les principales pérovskites étudiées, BaTiO3 et YBa2Cu3O7, possèdent d’intéressantes propriétés ferroélectriques et supraconductrices. Une des limitations de ce type d’oxydes est la transition de phase à haute température qui peut modifier leurs propriétés. Le matériau CaCu3Ti4O12 (CCTO) est un oxyde connu comme double perovskite (ABO3) à structure cubique, qui a été étudié ces dernières années en tant que matériau diélectrique de permittivité élevée. De plus, CCTO subit une transition magnétique à antiferromagnétique au-dessous de la température de Néel (TN=25K). Les propriétés du matériau CCTO sont fortement dépendantes de sa structure et offrent des possibilités d’applications photoélectrochimiques. D'un autre côté, les nanofeuillets de nitrure de bore (h-BN) et d’oxyde de graphène (GO) sont des matériaux 2D présentant des propriétés très intéressantes.Dans le cadre de ce travail, des matériaux composites à base de CCTO et de nanofeuillets de nitrure de bore et d’oxyde de graphène ont été synthétisés et étudiés. Les céramiques composites CCTO/GO et CCTO/h-BN ont été synthétisées par réaction solide-solide. Les différentes propriétés photoélectrochimiques, diélectriques, et magnétiques ont été caractérisées. L’addition de 3% de h-BN aboutit à l’incorporation des atomes du bore et d’azote dans le réseau cristallin du CCTO et forme les liaisons Ti-B-O et Ti-N-O, et génère des lacunes d’oxygène à la surface, ce qui améliore la génération de porteurs de charges. La génération de porteurs de charges est augmentée en 50% par rapport au CCTO pur, après l’addition de 3% de GO, due à l’oxydation de GO à haute température qui réduit Ti4+ et Cu2+ en site actifs Ti3+ et Cu+ respectivement. Les propriétés magnétiques du CCTO avec 6% de nanofeuillets ont été étudiées, et ont montré que la température Néel n’était pas modifiée. Enfin, un polissage est effectué à la surface des céramiques pour étudier leurs propriétés diélectriques. Les résultats montrent des valeurs de permittivité plus basse que celles décrites dans la littérature. En conclusion, ces travaux ont démontré que l’incorporation des nanofeuillets 2D n’affecte pas les propriétés diélectriques et magnétiques, mais améliore considérablement les propriétés photoélectrochimiques du CCTOPerovskite oxides exhibit a large variety of properties because of their structures and chemical compositions. Well known properties of the perovskite oxides are Ferroelectricity in BaTiO3-based oxides and superconductivity in YBa2Cu3O7. The major limit of these compounds is their phase transitions at high temperature, which lead to modify the perovskite properties. CaCu3Ti4O12 (CCTO) exhibit a cubic structure stable at high temperature, it is a double-perovskite (ABO3). CCTO was known as high dielectric material, and can play a key role in photoelectrochemical activity due to its structure. In addition, CCTO can occur a phase transition into the antiferromagnetically ordered phase below Neel temperature TN = 25 K. On the other hand, 2D nanomaterials including graphene oxide (GO) and hexagonal boron nitrides (h-BN) were widely used due their exceptional properties.The aim of this thesis is to investigate the photoelectrochemical, dielectric, and magnetic properties of CCTO based composites. Composites made of CCTO/GO and CCTO/h-BN ceramics were fabricated by solid-state reaction. With the addition of 2D nanosheets materials, the photoelectrochemical performance is enhanced by increasing the generation of photocurrent. CCTO with 3%wt of h-BN showed the insertion of bore (B) and nitrogen (N) into CCTO lattice, leading to Ti-B-O, Ti-N-O bonds and oxygen vacancies on the surface which reduce the bang gap energy and increase the density of generated photocurrent. With 3% of GO, Ti4+ and Cu2+ were reduced to active species Ti3+ and Cu+ respectively and oxygen vacancies were generated at the surface for charge neutralization, leading to generate photocurrent density 50% higher than pure phase of CCTO. In order to investigate 2D nanomaterials effects on magnetic properties of composites, CCTO with 6%wt of nanosheets was prepared and have shown no significant changes in Neel temperature. Finally in the last section, all composites were surface polished to investigate their dielectric properties, measurements showed a low permittivity in comparison to the literature. In conclusion, this work has shown that 2D nanosheets materials incorporation does not affect dielectric and magnetic properties, but enhance strongly the photoelectrochemical behavior of CCTO
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Bartoletti, Andrea. "Sintesi e caratterizzazione di CaCu3Ti4O12 (CCTO) per applicazioni in fotoelettrocatalisi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20682/.
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A promising strategy to mitigate both the energy crisis and global warming is the development of solar fuels and chemicals using as feedstock CO2 in combination with simple molecules such as water. This process stores the solar energy into chemical bonds, leading to a carbon-neutral approach of fuels and chemicals production. Aim of this thesis was the synthesis and characterization of CaCu3Ti4O12 (CCTO)- based compounds to be used as visible light photocatalyst for CO2 to chemical conversion. Different compositions were produced doping CCTO with increasing concentration of iron into the perovskite’s A site in order to identify the materials with the highest photo- and photoelectrocatalytic properties. The most promising compositions were used to produce photoelectrodes by screen printing that were characterized by linear and cyclic voltammetry, impedance spectroscopy and Mott-Schottky analysis to evaluate the electrical conductivity and calculate the flat band potential and the number of charge carriers in the samples. The photoelectrodes were then tested in a photoelectrochemical (PEC) cell for the conversion of CO2 into fuel and chemicals. The results obtained confirm that CCTO-based materials can be considered promising materials for carbon dioxide photo-electrochemical reduction.
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Jesus, Lilian Menezes de. "Sinterização a laser e caracterização dielétrica de cerâmicas de CaCu3Ti4O12." Pós-Graduação em Física, 2013. https://ri.ufs.br/handle/riufs/5289.
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Structural studies with CaCu3Ti4O12 (CCTO) are made since the 1970s, however investigations about their electrical properties only started recently. At 2000, it was reported a high permittivity of ~ 12000 (at 1 KHz) in ceramics of this material which remained constant between the room temperature to ~ 200 °C, and whose physical explanations be still controversial in the scientific society. High dielectric constants allow smaller capacitive components, enabling the size reduction of the electronic devices. In this way, CCTO has attracted the interest of many researchers as technological as scientific point of view. One of the main problem that limit its immediate application as dielectric in ceramic capacitors is its high dielectric loss (~ 0,15) near at room temperature. On the other hand, this material has been prepared by several researchers mainly by the solid state reaction method, in the temperature range of 1000 °C to 1050 °C, with thermal treatment up to 48 h. As result, some secondary phases have be found as in the calcined powders as in the sintered ceramics. Thus, other synthesis methods have been proposed and tested in the last years. In this work, we have studied the CCTO synthesis by a route based on Pechini s method and its sintering using a new method, in which a CO2 laser is used as the main heating source. Besides, the dielectric properties of CCTO ceramics were investigated in order to verify the influence of this sintering process on the ceramic properties as well as onto the understanding of the involved physical mechanisms. The laser sintered ceramics presented high relative density (95 ± 1%), with homogeneous microstructure and dielectric constant at about 2000 with low dielectric loss (0,06) at 1 kHz, when sintered at 1,3 W/mm2. The dielectric loss value obtained in this work is among the lowest ever recorded. Based on our results was also proposed a mechanism to aid in the understanding of the giant dielectric constant in CCTO. Finally, we believe that laser sintering can be an important tool for the optimization of the dielectric properties of CCTO ceramics and consequently future applications in the capacitors and electronic devices industry, whose worldwide consumption is increasing.Estudos estruturais com o CaCu3Ti4O12 (CCTO) são feitos desde os anos 1970, contudo investigações acerca de suas propriedades elétricas somente se iniciaram recentemente. Em 2000, foi reportado uma alta permissividade de ~ 12000 (a 1 kHz) em cerâmicas deste material, que permanecia constante da temperatura ambiente a ~ 200 °C, cujas explicações físicas ainda são bem controversas na comunidade científica. Constantes dielétricas altas permitem menores componentes capacitivos, oferecendo assim a oportunidade de diminuir o tamanho de dispositivos eletrônicos. Desta forma, o CCTO tem atraído muito o interesse de pesquisadores, tanto do ponto de vista tecnológico quanto científico. Um dos principais problemas que limitam sua imediata aplicação como dielétrico em capacitores cerâmicos é a sua alta perda dielétrica (~ 0,15) próximo à temperatura ambiente. Por outro lado, este material tem sido preparado por diversos pesquisadores principalmente pelo método da reação de estado sólido, no intervalo de temperatura de 1000 °C a 1100 °C, com tratamentos térmicos de até 48 h. Como resultado, algumas fases secundárias têm sido encontradas tanto no pó calcinado quanto na cerâmica sinterizada. Dessa forma, outros métodos de síntese vêm sendo procurados e testados nos últimos anos. Neste trabalho, estudamos a síntese do CCTO por uma rota baseada no método Pechini e sua sinterização usando um novo método, no qual um laser de CO2 é usado como principal fonte de aquecimento. Além disso, estudamos as propriedades dielétricas das cerâmicas de CCTO, a fim de verificar a influência deste novo processo de sinterização em suas propriedades bem como no entendimento dos mecanismos físicos envolvidos. As cerâmicas sinterizadas a laser apresentaram alta densidade relativa (95 ± 1%), com microestrutura homogênea e constante dielétrica em torno de 2000 e baixa perda dielétrica (0,06) a 1 kHz, quando sinterizadas a 1,3 W/mm2. O valor de perda dielétrica obtida neste trabalho está entre os mais baixos já registrados. Baseando-se em nossos resultados também foi proposto um mecanismo para auxiliar no entendimento da constante dielétrica gigante no CCTO. Finalmente, acreditamos que a sinterização a laser pode ser uma importante ferramenta para a otimização das propriedades dielétricas de cerâmicas de CCTO e consequentemente futuras aplicações na indústria de capacitores e dispositivos eletrônicos, cujo consumo mundial é cada vez maior.
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Felix, Anderson André [UNESP]. "Propriedades multifuncionais do CaCu3Ti4O12: estudo dos mecanismos e suas aplicações." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/106661.
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felix_aa_dr_bauru.pdf: 2060011 bytes, checksum: 4a5c68d1fc6a532384cd2520a68edde4 (MD5)Neste trabalho pastilhas cerâmicas de CaCu3Ti4O12 (CCTO) foram produzidas pelo método de reação por estado sólido onde estudos por difração de raios-X mostraram que as amostras policristalinas são monofásicas dependendo da pressão parcial de oxigênio. Estudos por microscopia eletrônica de varredura e fotoluminiscência indicam que o processo de crescimento de grão e densificação das amostras e a formação de vacâncias de oxigênio estão diretamente relacionados a concentração de oxigênio durante o processo de sinterização. As amostras foram caracterizadas por medidas elétricas dc em função da temperatura, que associada a teoria de semicondutores, provaram que as barreiras de potencial no CCTO são mais influenciadas pela temperatura do que pelo campo elétrico, ou seja, são barreiras do tipo Schottky. Um modelo de barreira e os mecanismos de formação foram propostos para descrever a formação da barreira de potencial no CCTO. Medidas de corrente-tensão cíclicas mostraram que o efeito de comutação resistiva no CCTO está diretamente relacionado a efeitos de contorno de grão e efeito Joule. As propriedades de transporte elétrico em filmes finos de CCTO foram investigadas para os efeitos de comutação resistiva, retificação elétrica e aplicação em sensores de gás. Filmes monofásicos foram produzidos pelo Método dos Precursores Poliméricos (MPP) em diferentes tipos de substratos. Filmes produzidos em substratos de LNO/Si apresentam curvas de corrente-tensão simétricas, indicando contatos ôhmicos, enquanto os filmes depositados sobre substratos de Pt/Si têm um comportamento altamente assimétrico nestas curvas, o qual está relacionada com a formação de um junção metal-semicondutor na interface CCTO/Pt. Os resultados indicam que a formação deste tipo de contato reforça o efeito de comutação resistiva neste material...
CaCu3Ti4O12 (CCTO) pellets were produced by solid state reaction method and X-ray diffractograms showed that single phase polycrystalline samples were obtained. Studies by scanning electron microscopy and photoluminescence indicate that the process of growth and densification of the samples and formation of oxygen vacancies, respectively, are directly related to oxygen concentration during sinterization process. The samples were electrically characterized by dc measurements a function of temperature, which associated to semiconductor theory, showed that CCTO barriers are more influenced by temperature than by electric filed, i.e., Schottky barriers. A model and the mechanism for barrier formation have been proposed to describe the CCTO potential barrier. Electric transport properties of CaCu3Ti4O12 (CCTO) thin films were investigated for resistive switching, rectifying and gas sensor applications. Single phase CCTO thin films were produced by Polymeric Precursor Method (PPM) on different substrates. Cyclic current-voltage measurements showed that resistive switching effects in CCTO is directly related to the grain boundary and Joule effects. Films produced on LNO/Si substrates have symmetrical non-ohmic current voltage characteristics, forming ohmic contact, while films deposited on Pt/Si substrates have a highly asymmetrical non-ohmic behavior which is related to a metal-semiconductor (MS) junction formed at the CCTO/Pt interface. Results confirm that CCTO has a resistive switching response which is enhanced by Schottky contacts. Sensor response tests revealed that CCTO films are sensitive to oxygen gas and exhibit n-type conductivity. These results demonstrate the versatility of CCTO thin film prepared by the PPM method for gas atmosphere or bias dependent resistance applications depending n filme configuration
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Felix, Anderson André. "Propriedades multifuncionais do CaCu3Ti4O12 : estudo dos mecanismos e suas aplicações /." Bauru, 2013. http://hdl.handle.net/11449/106661.
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Orientador: José Arana VarelaBanca: Miguel Angel Ramirez Gil
Banca: Paulo Noronha Lisboa Filho
Banca: Paulo Roberto Bueno
Banca: Sidnei Antonio Pianaro
O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp
Resumo: Neste trabalho pastilhas cerâmicas de CaCu3Ti4O12 (CCTO) foram produzidas pelo método de reação por estado sólido onde estudos por difração de raios-X mostraram que as amostras policristalinas são monofásicas dependendo da pressão parcial de oxigênio. Estudos por microscopia eletrônica de varredura e fotoluminiscência indicam que o processo de crescimento de grão e densificação das amostras e a formação de vacâncias de oxigênio estão diretamente relacionados a concentração de oxigênio durante o processo de sinterização. As amostras foram caracterizadas por medidas elétricas dc em função da temperatura, que associada a teoria de semicondutores, provaram que as barreiras de potencial no CCTO são mais influenciadas pela temperatura do que pelo campo elétrico, ou seja, são barreiras do tipo Schottky. Um modelo de barreira e os mecanismos de formação foram propostos para descrever a formação da barreira de potencial no CCTO. Medidas de corrente-tensão cíclicas mostraram que o efeito de comutação resistiva no CCTO está diretamente relacionado a efeitos de contorno de grão e efeito Joule. As propriedades de transporte elétrico em filmes finos de CCTO foram investigadas para os efeitos de comutação resistiva, retificação elétrica e aplicação em sensores de gás. Filmes monofásicos foram produzidos pelo Método dos Precursores Poliméricos (MPP) em diferentes tipos de substratos. Filmes produzidos em substratos de LNO/Si apresentam curvas de corrente-tensão simétricas, indicando contatos ôhmicos, enquanto os filmes depositados sobre substratos de Pt/Si têm um comportamento altamente assimétrico nestas curvas, o qual está relacionada com a formação de um junção metal-semicondutor na interface CCTO/Pt. Os resultados indicam que a formação deste tipo de contato reforça o efeito de comutação resistiva neste material... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: CaCu3Ti4O12 (CCTO) pellets were produced by solid state reaction method and X-ray diffractograms showed that single phase polycrystalline samples were obtained. Studies by scanning electron microscopy and photoluminescence indicate that the process of growth and densification of the samples and formation of oxygen vacancies, respectively, are directly related to oxygen concentration during sinterization process. The samples were electrically characterized by dc measurements a function of temperature, which associated to semiconductor theory, showed that CCTO barriers are more influenced by temperature than by electric filed, i.e., Schottky barriers. A model and the mechanism for barrier formation have been proposed to describe the CCTO potential barrier. Electric transport properties of CaCu3Ti4O12 (CCTO) thin films were investigated for resistive switching, rectifying and gas sensor applications. Single phase CCTO thin films were produced by Polymeric Precursor Method (PPM) on different substrates. Cyclic current-voltage measurements showed that resistive switching effects in CCTO is directly related to the grain boundary and Joule effects. Films produced on LNO/Si substrates have symmetrical non-ohmic current voltage characteristics, forming ohmic contact, while films deposited on Pt/Si substrates have a highly asymmetrical non-ohmic behavior which is related to a metal-semiconductor (MS) junction formed at the CCTO/Pt interface. Results confirm that CCTO has a resistive switching response which is enhanced by Schottky contacts. Sensor response tests revealed that CCTO films are sensitive to oxygen gas and exhibit n-type conductivity. These results demonstrate the versatility of CCTO thin film prepared by the PPM method for gas atmosphere or bias dependent resistance applications depending n filme configuration
Doutor
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Vaz, Isabela Cristina Fernandes. "Síntese e caracterização de CaCu3Ti4O12 com doadores de elétrons Nb E Mo." reponame:Repositório Institucional da UNIFEI, 2016. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1654.
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A miniaturização de dispositivos eletrônicos mais rápidos e eficientes tem sido um desafio. para o desenvolvimento de novos dispositivos eletroeletrônicos com isso o estudo de. cerâmicas multifuncionais vem aumentando. A descoberta da permissividade dielétrica (). gigante de aproximadamente 105 e o coeficiente não linear (α) no CaCu3Ti4O12 (CCTO). despertou grande interesse por oferecer a oportunidade de reduzir o tamanho e otimizar as. propriedades nos dispositivos eletrônicos. No presente trabalho propôs analisar e estudar as. propriedades estruturais, microestruturais e elétricas do titanato de cobre e cálcio dopado com. molibdênio (1,00%; 2,00%; 3,00%; 4,00% e 5,00% em mol) e nióbio (1,00%; 2,00%; 3,00%;. 4,00% e 5,00% em mol) no sítio B. O processo de síntese adotado para a obtenção das. cerâmicas foi o “método tradicional de mistura de óxidos” ou reação no estado sólido, visando. à obtenção de produtos com microestrutura homogênea. Os pós foram termicamente avaliados. pela análise termogravimétrica (TG), análise térmica diferencial (DTA) e dilatometria.. Estruturalmente, os pós foram caracterizados por difração de raios X (DRX), espectroscopia. de espalhamento Raman e espectroscopia de absorção na região de infravermelho por. transformada de Fourier (FT-IR). A forma, o tamanho dos grãos e os contornos de grão foram. observados por intermédio da microscopia eletrônica de varredura (MEV). As propriedades. óticas foram investigadas por espectroscopia ótica nas regiões do ultravioleta e visível (UVVis). Os padrões de DRX indicaram a formação de soluções sólidas homogênea com estrutura. perovskita, pertencentes ao grupo espacial Im3 para todas as concentrações de Nb calcinada a. 950°C avaliadas e apenas para a concentração de 1% de Mo calcinada a 850°C. Os ajustes. teóricos dos espectros Raman indicaram a formação de fase secundária para todas as. concentrações e temperatura, mostrando que a formação da solução sólida homogênea. ocorreu apenas em longo alcance. As imagens de microscopia indicaram que os dopantes. diminuem o tamanho do grão e alteram a sua morfologia em que o nióbio deixa os grãos. hexagonais e o molibdênio os grãos esféricos. Por último, foram avaliadas as propriedades. elétricas por medidas de tensão – corrente e espectroscopia de impedância. Pôde-se observar. que as cerâmicas dopadas com Mo modificou as propriedades não-ôhmica do CCTO, não. sendo possível verificar uma possível aplicação em dispositivos varistores devido ao alto. campo necessário para a ruptura da cerâmica. Já as cerâmicas dopadas com nióbio. apresentaram características não lineares com um decréscimo da tensão de ruptura com o. aumento da concentração do dopante indicando sua aplicação como dispositivo de proteção. elétrica de baixa tensão “varistor”
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Sun, Yang. "Dielectric Properties of CaCu3Ti4O12 and Its Related Materials." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1153884252.
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Barbier, Bertrand. "Elaboration et caractérisation de condensateurs à base de CaCu3Ti4O12 à forte permittivité relative pour l'électronique de puissance." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/547/.
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Les céramiques massives issues de poudres de CaCu3Ti4O12 (CCTO) élaborées par co-précipitation suivie d'un traitement de calcination présentent des permittivités relatives colossales (150 000 à 1 kHz, Tamb), qui dépendent du taux de phase additionnelle CuO. L'étude confirme que le modèle de barrière interne est à l'origine de ces permittivités relatives. Par ailleurs, les caractérisations en tension et en impédance ont permis d'établir un modèle comportemental grâce à un circuit électrique équivalent facilement utilisable lors de simulations. Une étude originale a été menée sur des couches de CCTO mises en forme par coulage en bandes. Ces couches présentent des permittivités relatives très élevées (47 000 à 1 kHz, Tamb) pour les épaisseurs supérieures ou égales à 40 µm. Une chute brutale de la permittivité relative est observée pour les épaisseurs inférieures à 40 µm, et est liée au nombre insuffisant de barrières internes (joints de grains) électriquement actives. Des condensateurs céramiques multicouches présentant des structures internes et des propriétés électriques reproductibles ont été élaborés. Les valeurs de capacité ont été considérablement augmentées (jusqu'à 1,4 µF à 1 kHz, Tamb) et les valeurs de résistance série fortement diminuées (jusqu'à 0,3 O) par rapport aux céramiques massives. Concernant la tenue en tension, il est primordial de prendre en compte le comportement non linéaire du courant avec la tension, caractéristique de CCTO. La comparaison avec des diélectriques usuels (type Z5U) a permis de montrer que les composants élaborés présentent de meilleures caractéristiques en température et en vieillissementMassive ceramics prepared from CaCu3Ti4O12 (CCTO) powders obtained by coprecipitation method and a calcination show colossal relative permittivities (150 000 at 1 kHz, RT), thanks to the control of additional CuO phase. The study has confirmed that the observed properties can be explained by the internal barrier model. Furthermore, the voltage and impedance characterizations allowed us to create a behavioral model with an equivalent electric circuit readily usable in simulations. An original study was conducted on CCTO films shaped by tape casting method. The films show high relative permittivity values (47 000 at 1 kHz, RT) for thicknesses greater than 40 µm. Below 40 µm, a sharp drop of the relative permittivity is observed, due to an insufficient number of internal barriers (grain boundaries) electrically active. Multilayer ceramic capacitors with reproducible internal structures and electrical properties were developed. The capacity values were significantly increased (1. 4 µF at 1 kHz, RT) and equivalent serial resistances were significantly decreased (0. 3 O), compared to massive ceramics. Regarding the tension strength, the nonlinear current-voltage behavior is an interesting characteristic of CCTO. The comparison with usual dielectrics (Z5U) has shown that the as-developed components exhibit higher temperature and aging characteristics
Book chapters on the topic "CaCu3Ti4O12"
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Saari, Muhammad Qusyairie, Nur Shafiza Afzan Mohd Shariff, Hasmaliza Mohamad, Mohd Fariz Ab Rahman, Zainal Arifin Ahmad, Mohamad Kamarol Mohd Jamil, and Julie Juliewatty Mohamed. "Effect of ZnO-B2O3-SiO2 (ZBS) Glass Additives to the Properties of CaCu3Ti4O12 Electroceramic." In Lecture Notes in Mechanical Engineering, 941–49. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0866-7_82.
Full textConference papers on the topic "CaCu3Ti4O12"
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Li, S. T., and Y. Yang. "Conduction properties of CaCu3Ti4O12." In 2008 International Symposium on Electrical Insulating Materials (ISEIM). IEEE, 2008. http://dx.doi.org/10.1109/iseim.2008.4664595.
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Kwon, S., N. Triamnak, and D. P. Cann. "Decomposition kinetics of CaCu3Ti4O12." In 2008 17th IEEE International Symposium on the Applications of Ferroelectrics (ISAF). IEEE, 2008. http://dx.doi.org/10.1109/isaf.2008.4693893.
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Cheng, Pengfei, Hanchen Liu, Lixun Song, and Caijuan Xia. "Dielectric response of CaCu3Ti4O12 materials." In 2011 Second International Conference on Mechanic Automation and Control Engineering. IEEE, 2011. http://dx.doi.org/10.1109/mace.2011.5988735.
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Kulawk, J., D. Szwagierczak, and B. Synkiewicz. "Multilayer ceramic capacitors with CaCu3Ti4O12 dielectric." In 2012 Joint 21st IEEE ISAF / 11th IEEE ECAPD / IEEE PFM (ISAF/ECAPD/PFM). IEEE, 2012. http://dx.doi.org/10.1109/isaf.2012.6297757.
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Hui Wang, Shengtao Li, Chunjiang Lin, Jianying Li, and Mingzhe Rong. "Dielectric properties of CaCu3Ti4O12 thick films." In 2012 IEEE 10th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2012. http://dx.doi.org/10.1109/icpadm.2012.6319018.
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Saboia, K. D. A., H. T. Girao, A. S. B. Sombra, M. P. F. Graca, L. C. Costa, F. Amaral, and M. A. Valente. "Microwaves dielectric properties of Y3Fe5O12-CaCu3Ti4O12 composites." In 2011 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC). IEEE, 2011. http://dx.doi.org/10.1109/imoc.2011.6169310.
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Shengtao Li, Yang Yang, Wang Hui, and Jianying Li. "Dielectric properties of B-doped CaCu3Ti4O12 ceramics." In 2011 International Symposium on Electrical Insulating Materials (ISEIM). IEEE, 2011. http://dx.doi.org/10.1109/iseim.2011.6826318.
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Rahman, Mohd Fariz Ab, Mohamad Johari Abu, Saniah Ab Karim, Rosyaini Afindi Zaman, Mohd Fadzil Ain, Zainal Arifin Ahmad, and Julie Juliewatty Mohamed. "Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite." In THE 2ND INTERNATIONAL CONFERENCE ON FUNCTIONAL MATERIALS AND METALLURGY (ICoFM 2016). Author(s), 2016. http://dx.doi.org/10.1063/1.4958750.
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Ashokbabu, A., and P. Thomas. "Preparation and Characterization of Nylon 11/CaCu3Ti4O12 (CCTO) Nanocomposites." In 2018 15th IEEE India Council International Conference (INDICON). IEEE, 2018. http://dx.doi.org/10.1109/indicon45594.2018.8987038.
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Yu, Rong, La Chen, Hao Xue, and Zhaoxian Xiong. "Preparation and dielectric properties of CaCu3Ti4O12-(NaBi)0.5Cu3Ti4O12 composites." In 2011 International Symposium on Advanced Packaging Materials (APM). IEEE, 2011. http://dx.doi.org/10.1109/isapm.2011.6105669.
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