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Rozprawy doktorskie na temat „Pyrochlore structure”

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Data publikacji: 2 czerwca 2025
Data aktualizacji: 31 lipca 2025

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1

Mostaed, Ali. "Atomic structure study of pyrochlore ytterbium titanate." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/96357/.

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There has been great interest in the magnetic behaviour of pyrochlore oxides with the general formula A2B2O7, in which rare-earth (A), and transition metal (B) cations are ordered on separate interpenetrating lattices of corner-sharing tetrahedra. Such materials exhibit behaviours including quantum spin-ice, (quantum) spin-liquid, and ordered magnetic ground states. Yb2Ti2O7 lies on the boundary between a number of competing magnetic ground states. Features in the low-temperature specific heat capacity that vary in sharpness and temperature from sample to sample suggest that in some cases the
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2

Galati, Rosa. "Synthesis, structure and properties of heavy metal pyrochlore oxides." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/173963/.

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Many interesting and often exotic magnetic phenomena have been observed over the past twenty years in the family of the heavy metal pyrochlore oxides, A2B2O6O’. In these systems, competing interactions are common and tend to emerge mainly at low temperatures. Magnetic properties are related to the contribution of d orbitals that transition metal (TM) offer and their interplay with the positive contribution coming from the cation sitting on the A site. The work described in this thesis explores the effects of chemical substitution of the A site cation on the symmetry and the properties of a num
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Rivière, Martine. "Synthèse, structure et propriétés de conducteurs protoniques de type pyrochlore." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37600815m.

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Walker, Robert. "The surface chemistry and bulk electronic structure of bismuth based pyrochlore oxides." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/48468.

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Metal oxides of bismuth show applications from photocatalysts to dielectric materials often due to the influence of the so called “lone pair” electrons that give rise to structural distortions and modified electronic structure. These effects upon which fundamental properties are derived are still not yet fully understood. Polycrystalline Bi 2 Ti 2 O 7 , Bi 2 Zr 2 O 7 , and Bi 2 Hf 2 O 7 materials - the latter in both pyrochlore (p) and monoclinic (m) phases - were prepared via co-precipitation and, except for Bi 2 Hf 2 O 7 (m), thin films. The bulk, surface, and electronic properties were char
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5

Tolla, Bruno. "Phénomènes d'échange d'oxygène au sein de nouveaux stannates de cérium de structure pyrochlore : défauts et mécanismes." Bordeaux 1, 1999. http://www.theses.fr/1999BOR10583.

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Ce travail concerne l'etude des proprietes d'echange d'oxygene de la solution solide pyrochlore ce 2sn 2o 7-ce 2sn 2o 8. La synthese d'un nouveau stannate ce 2sn 2o 7, ou le cerium est au degre d'oxydation iii, a ete mise au point. Sa structure a ete determinee par diffraction de neutrons. Ce compose est susceptible d'intercaler des 400\c un atome d'oxygene par unite formulaire. Une experience de diffraction de neutrons, completee par des mesures de spectroscopie a l'echelle locale (ir/raman, exafs, rmn 1 1 9sn/ 1 7o), permet de caracteriser deux types de defauts au sein du nouveau reseau qui
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6

Thuries, Fabienne. "Préparation et étude cristallographique de niobates et tantalates de plomb à structure dérivée de la phase pyrochlore." Aix-Marseille 3, 1995. http://www.theses.fr/1995AIX30016.

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Au cours de ce travail, nous avons identifie les oxydes obtenus avec les cristaux de pb#2sctao#6 (pst) et pb#2sc(nb#0#,#5ta#0#,#5)o#6 qui sont etudies pour leurs proprietes dielectriques. Ce sont des tantalates de plomb contenant une proportion en scandium tres inferieure a celle de pst et presentant une structure cubique de type pyrochlore. Dans un deuxieme temps, nous avons elabore des cristaux de niobate et tantalate de plomb, a partir des compositions: 2pbo-1nb#2o#5 et 2pbo-1ta#2o#5. Il s'avere que les phases obtenues ne sont pas stchiometriques et presentent un exces de plomb par rapport
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7

Lutique, Stéphanie. "Etude de zirconates de structure pyrochlore en tant que matrice pour la transmutation ou le conditionnement des actinides mineurs." Paris 11, 2003. http://www.theses.fr/2003PA112080.

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La loi "Bataille" définit le cadre des études pour une gestion optimisée des déchets nucléaires, incluant la séparation des éléments les plus radiotoxiques pour les transmuter en élément moins radiotoxiques ou les stocker à long terme. Ces deux applications nécessitent l'utilisation d'une matrice répondant à plusieurs critères spécifiques. Ce travail effectué au cours de la thèse a pour but d'étudier une matrice potentielle pour la transmutation ou le stockage des actinides après leur séparation: le zirconate de type pyrochlore A2Zr2O7 (A est un lanthanide ou un actinide). Le développement d'u
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8

Roger, Anne-Cécile. "Couplage oxydant du methane sur des catalyseurs de structure definie de type pyrochlore a#2b#2o#7 (a = sm ; b = sn)." Université Louis Pasteur (Strasbourg) (1971-2008), 1995. http://www.theses.fr/1995STR13058.

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Ce travail porte sur la preparation d'une famille de structures definies derivant de la pyrochlore sm#2sn#2o#7 et sur le comportement catalytique de ces structures vis a vis de la reaction de couplage oxydant du methane. La maitrise et la reproductibilite de la synthese, par une methode de type sol-gel (methode des resines), ont ete atteintes par une etude approfondie des especes intermediaires de la preparation. La solubilisation des sels cationiques (samarium et etain) dans l'acide propionique a ete suivie par infra-rouge et rmn de #1#1#9sn. Ces etudes ont permis de proposer des modeles pour
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9

Rivière, Martine. "Synthèse, structure et propriétés de conducteurs protoniques de type pyrochlore : la série H2xSb2xW2-2xo6h2o et la phase Al2[(OH)0,5F0,5]6.H2O." Le Mans, 1986. http://www.theses.fr/1986LEMA1009.

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Obtention des phases du titre par chimie douce. Localisation des molecules d'eau par diffraction rx et diffraction de neutrons. Les mesures de conductivite electrique effec tuees par la methode des impedances complexes dans des atmospheres a humidite controlee revelent l'influence tres importante de l'eau physiquement absorbee
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10

Andrade, M. B., H. Yang, D. Atencio, et al. "Hydroxycalciomicrolite, Ca1.5Ta2O6(OH), a new member of the microlite group from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil." MINERALOGICAL SOC, 2017. http://hdl.handle.net/10150/625066.

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Hydroxycalciomicrolite, Ca1.5Ta2O6(OH) is a new microlite-group mineral found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. It occurs as isolated octahedral and as a combination of octahedral and rhombic dodecahedral crystals, up to 1.5 mm in size. The crystals are yellow and translucent, with a white streak and vitreous to resinous lustre. The mineral is brittle, with a Mohs hardness of 56. Cleavage is not observed and fracture is conchoidal. The calculated density is 6.176 g cm(3). Hydroxycalciomicrolite is isotropic, n(calc). = 2.010. The infrared and Raman spectra exhibit
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11

Mitchell, Martin R. "Investigation of structure and disorder in inorganic solids using solid-state NMR." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3367.

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The use of solid-state NMR and DFT calculations to study Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇, Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ and Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇, materials with applications for the safe encapsulation of radioactive actinides is investigated. As a result of cation or anion disorder in these materials, NMR spectra are often complex and difficult to interpret. Therefore, an investigation using a range of NMR active nuclei and measurement of a variety of NMR parameters (isotropic chemical shift, δ[subscript(iso)]; span, Ω and quadrupolar coupling, C[subscript(Q)]
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12

Mergen, Ayhan. "Electrical ceramics with the pyrochlore crystal structure in the ZnO-Bi←2O←3-Sb←2O←3 and PbO-MgO-Nb←2O←5 systems." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387794.

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13

Wilde, Peter Joseph. "The defect chemistry of pyrochlore structured oxides." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309471.

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14

Chapuis, Yann. "Frustration géométrique, transitions de phase et ordre dynamique." Phd thesis, Grenoble 1, 2009. http://www.theses.fr/2009GRE10130.

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Cette thèse traite de composés magnétiques géométriquement frustrés, cristallisant dans la structure pyrochlore, c'est-à-dire un arrangement tri-dimensionnel de tétraèdres reliés entre eux par leurs sommets. Tout d'abord, on montre que le liquide de spins Tb2Ti2O pose un certain nombre de difficultés quant à sa fabrication, certaines propriétés physiques mesurées étant très dépendantes des conditions de croissance. Cependant, deux températures caractéristiques, indépendantes des échantillons, à 2 et 50 K, ont pu être mises en évidence par différentes techniques expérimentales, et ce, sur diffé
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15

Chapuis, Yann. "Frustration géométrique, transitions de phase et ordre dynamique." Phd thesis, Grenoble 1, 2009. http://tel.archives-ouvertes.fr/tel-00463643.

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Cette thèse traite de composés magnétiques géométriquement frustrés, cristallisant dans la structure pyrochlore, c'est-à-dire un arrangement tri-dimensionnel de tétraèdres reliés entre eux par leurs sommets. Tout d'abord, on montre que le liquide de spins Tb2Ti2O7 pose un certain nombre de difficultés quant à sa fabrication, certaines propriétés physiques mesurées étant très dépendantes des conditions de croissance. Cependant, deux températures caractéristiques, indépendantes des échantillons, à 2 et 50 K, ont pu être mises en évidence par différentes techniques expérimentales, et ce, sur diff
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16

Yu, Tae-Hwan. "Electrical properties and structural disorder in stannate pyrochlores." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40609.

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Daniels, Luke M. "Structures and properties of perovskites and pyrochlores from hydrothermal synthesis." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/77054/.

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The hydrothermal syntheses of new complex pyrochlore and perovskite oxide materials have been explored. Disorder is prevalent in these materials, so their structures and properties were investigated using a wide range of techniques. New pyrochlore oxides with compositions (Na0:60Bi1:40)(Fe1:06Mn0:17Bi0:77)O6:87 and (K0:24Bi1:51)(Fe1:07Mn0:15Bi0:78)O6:86 were hydrothermally produced in solutions of NaOH or KOH, respectively, at 200oC for 6 hours. These pyrochlores are metastable, decomposing at ca 400oC, suggesting their formation would be impossible through conventional solid state synthesis.
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18

Baroudi, Kristen. "Synthesis and characterization of novel magnetically frustrated oxides with honeycomb and pyrochlore structures." Thesis, Princeton University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3712079.

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<p> In this thesis I present the synthesis and characterization of materials exhibiting frustrated magnetism. In Chapter 1 I describe magnetic frustration and some of the magnetic states that can arise from it followed by the background on iridates and platinates with honeycomb structures and rare earth pyrochlores. </p><p> In Chapter 3 I discuss my work on the synthesis and properties of ternary sodium iridates with formulas Na<sub>x</sub>M<sub>2/3</sub>Ir<sub>1/3</sub>O<sub> 2</sub> and Na<sub>x</sub>M<sub>1/3</sub>Ir<sub>2/3</sub>O<sub>2</sub> (M = Mn, Fe, Co, Ni, Cu, Zn). The ternary ir
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19

Payne, Julia Louise. "Synthesis, structure and properties of mixed metal oxides : from pyrochlores to fluorites." Thesis, Durham University, 2011. http://etheses.dur.ac.uk/646/.

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Introduction and Literature Review: Different families of oxide ion conductors and their applications are discussed. Experimental and Characterisation Methods: The synthetic methods and characterisation techniques used throughout this thesis are described. Synthesis, Structure and Transport Properties of Bi2Zr2-xTixO7 Phases: The characterisation of Bi2Zr2-xTixO7 compounds is reported for the first time. An increase in conductivity of 3 orders of magnitude is found for the Zr- rich end member. Bi2Ti2O7, which adopts centrosymmetric space group Fd-3m has been found to be SHG active. Structure S
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Injac, Sean Dusan Alexander. "Structural and Magnetic Characterisation of 4d and 5d Mixed Metal Oxides." Thesis, The University of Sydney, 2019. https://hdl.handle.net/2123/21640.

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Advanced functional materials showing magnetic properties are a cornerstone of modern information technologies, and are keenly studied in order to search for useful materials within emerging technologies, such as spintronics, applied superconductivity and quantum computing. Magnetic materials containing the heavy 4d and 5d metals are relatively understudied compared to their 3d counterparts and are a promising avenue of study in this search for novel functional materials. This work presents the synthesis, structural, and magnetic characterisation of a number of novel 4d and 5d metal oxides wi
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21

Le, Bihan Vincent. "Interactions de nano-objets luminescents (agrégats ou nano-films) avec leurs environnements : effets structuraux et diélectriques." Phd thesis, Université Claude Bernard - Lyon I, 2008. http://tel.archives-ouvertes.fr/tel-00332025.

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Depuis la fin du 20ième siècle, l'étude de matériaux manométriques a permis la découverte de nouvelles propriétés liées à la taille. Ces "effets de taille" sont controversés car ils dépendent fortement de la méthode d'élaboration, de l'état de surface et structural du nano-système. Dans ce travail de thèse, nous étudions l'influence de l'environnement sur les propriétés structurales et diélectriques de nano-couche de Gd2O3:Eu3+ élaborées par deux techniques différentes.<br /><br /> Dans une première partie, nous analysons le comportement d'agrégats de Gd2O3:Eu3+ élaborés par la technique d'éva
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22

Pors, Françoise. "Préparation et caractérisation d'oxynitrures de type pérovskite, KNiF et pyrochlore étude structurale et diélectrique /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37608978q.

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Knapp, Meghan C. "Investigations into the structure and properties of ordered perovskites, layered perovskites, and defect pyrochlores." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149097068.

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Sneddon, Scott. "Characterisation of inorganic materials using solid-state NMR spectroscopy." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/8239.

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This thesis uses solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations to study local structure and disorder in inorganic materials. Initial work concerns microporous aluminophosphate frameworks, where the importance of semi-empirical dispersion correction (SEDC) schemes in structural optimisation using DFT is evaluated. These schemes provide structures in better agreement with experimental diffraction measurements, but very similar NMR parameters are obtained for any structures where the atomic coordinates are optimised, owing to the simila
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25

Shehu, Ali. "Structural analysis and its implications for oxide ion conductivity of lanthanide zirconate pyrochlores." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/36699.

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The local structure evolution as a function of composition and temperature, and the resulting electrical conductivities were studied in samples with general composition (Yb1-xNdx)2Zr2O7, using Reverse Monte Carlo (RMC) modelling of total neutron scattering data and Impedance Spectroscopy. At low neodymium content (0.00 ≤ x ≤ 0.50), this system crystallizes in the fluorite structure with space group Fm3̄m, where-as at high neodymium content (0.75 ≤ x ≤ 1.00), a pyrochlore structure with space group Fd3̄m is observed. For compositions with high neodymium content prepared at lower temperatures, a
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26

Maryasin, Vladimir. "Ordre par le désordre structural et les effets du champ magnétique dans les systèmes frustrés." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY051/document.

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La compétition des interactions est une caractéristique essentielle des systèmes frustrés, elle est à l'origine d'une large dégénérescence des états fondamentaux classiques ou, obtenus par une théorie de champ moyen.Fréquemment la dégénérescence peut être levée par des fluctuations thermiques ou quantiques, ce qui constitue la base du mécanisme appelé textit{ordre par le désordre}.Les systèmes magnétiques étudiés expérimentalement contiennent une quantité inévitable de désordre structural.Dans cette thèse de doctorat, l'influence des défauts, créé par des sites inoccupés ou par un désordre des
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Pors, Françoise. "Preparation et caracterisation d'oxynitrures de type perovskite, k::(2)nif::(4) et pyrochlore : etude structurale et dielectrique." Rennes 1, 1987. http://www.theses.fr/1987REN10071.

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Ce travail entre dans le cadre d'une etude systematique de la substitution de o par n dans le reseau anionique de differents types d'oxydes. Reparation des perovskites abo::(2)n ca: alcalinoterreux ou lanthanide, b: ta, nb ou ti) et abon::(2) (a: lanthanide, b: ta ou nb). Etude structurale de certains composes par diffraction de neutrons. Le type structural k::(2)nif::(4) est illustre par lu::(2)alo::(3)n (ln: la, nd, sm) et a::(2)tao::(3)n (a: sr, ba). Enfin, les phases de stoechiometrie ln::(2)ta::(2)o::(5)n::(2) constituent les premiers exemples d'oxynitrures a structure pyrochlore. Etude d
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28

Barnes, Paris W. "Exploring structural changes and distortions in quaternary perovskites and defect pyrochlores using powder diffraction techniques." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1064346592.

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Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xxvi, 255 p.; also includes graphics. Includes abstract and vita. Advisor: Patrick M. Woodward, Dept. of Chemistry. Includes bibliographical references (p. 221-228).
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29

Ramón, Jonathan Gustavo Acosta. "Vacâncias de oxigênio e diluição de ítrio no pirocloro geometricamente frustrado Gd2Ti2O7." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-22022016-170657/.

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O composto magnético geometricamente frustrado Gd2Ti2O7 da família dos pirocloros apresenta um comportamento bastante interessante, sendo que a natureza da fase magnética em baixas temperaturas se encontra ainda sob intenso debate. Este material entra em um estado antiferromagnético parcialmente ordenado à temperatura T1N ~ 1 K, apresentando outra transição de fase em T2N ~ 0.7 K. Neste trabalho é investigada a física de baixas temperaturas de amostras de Gd2Ti2O7 com defeitos estruturais tais como vacâncias de oxigênio e diluição de ítrio. Amostras policristalinas com composição Gd2Ti2O7 e Gd
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30

Apetrei, Anca Mihaela. "Etude des pyrochlores géométriquement frustrés R2M2O7 (M=Sn ou Mo). Influence des substitutions chimiques et/ou de la pression appliquée." Phd thesis, Université Paris Sud - Paris XI, 2007. http://tel.archives-ouvertes.fr/tel-00229792.

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Dans les oxydes R2M2O7, les deux ions R3+ (terre rare ou Y) et M4+ (M= métal sp ou de transition) occupent des réseaux pyrochlores géométriquement frustrés. Cette étude a pour objet l'analyse de deux types de systèmes: (i) Tb2Sn2O7, composé isolant dans lequel l'équilibre en énergie et l'état fondamental sont contrôlés par les interactions magnétiques entre les ions Tb3+ et (ii) la série (Tb1-xLax)2Mo2O7 (x=0-0.2), caractérisée par la présence du magnétisme localisé du Tb3+ et de celui partiellement itinérant du Mo4+. Nous avons étudié l'ordre magnétique principalement par diffraction de neutr
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Złotnik, Sebastian Czesław. "Functional alkali tantalate 2D structures for microelectronics and related applications." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/15893.

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Doutoramento em Ciência e Engenharia de Materiais<br>Alkali tantalates and niobates, including K(Ta / Nb)O3, Li(Ta / Nb)O3 and Na(Ta / Nb)O3, are a very promising ferroic family of lead-free compounds with perovskite-like structures. Their versatile properties make them potentially interesting for current and future application in microelectronics, photocatalysis, energy and biomedics. Among them potassium tantalate, KTaO3 (KTO), has been raising interest as an alternative for the well-known strontium titanate, SrTiO3 (STO). KTO is a perovskite oxide with a quantum paraelectric behaviour when
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32

Marrot, Jérôme. "Action de ciseaux chimiques sur des oxydes métalliques. Evolution et/ou adaptation structurale A M M* 05 E : une formule non usuelle pour pyrochlore, (A = alcalin, M = métal de transition, M* = élément à paire libre E)." Toulouse 3, 1995. http://www.theses.fr/1995TOU30182.

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Les etudes presentees dans ce memoire mettent en evidence un phenomene interessant: la notion de ciseau chimique. Dans les phases du systeme cao-v2o4 de formulation cavno2n+1, l'ajout de cao se traduit dans la structure par l'apparition de cisaillements cristallographiques. Les composes du systeme cao-v2o5 montrent une filiation entre le pentoxyde de vanadium, le metavanadate, le pyrovanadate et l'orthovanadate de calcium. Ici, l'action de cao est plus marquee. Les structures sont decoupees en blocs de dimensions de plus en plus petites. D'autres agents de coupure des structures sont les eleme
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33

Ruchaud, Nathalie. "Nouveaux matériaux fluorés à chaînes magnétiques : etudes physicochimiques de composés fluorés de palladium(II) de cuivre(II) et d'argent(I)." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1991. http://tel.archives-ouvertes.fr/tel-00163900.

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De nouveaux composés fluorés à chaines magnétiques appartenant aux types weberite et pyrochlore ont été isolés. Les corrélations entre propriétés structurales et magnétiques ont été étudiées. Plusieurs familles a base de palladium(II) ont été caractérisées. Des structures cristallines ont été déterminées (soit sur monocristal, soit sur des échantillons polycristallins par la méthode de Rietveld). Divers types structuraux ont été identifies (types CsPd2F5, LiSbF6 ou dérivant de Na2CuF4): le palladium y est localisé en site octaédrique ou plan carré mais peut posséder simultanément ces deux coor
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Caillault, Nathalie. "Systeme cuo-bi#2o#3-sb#2o#3 structures et proprietes electriques des ceramiques de type pyrochlore m#i#im#1#,#5#i#i#im#1#,#5#vo#7 (m#i#i=cu, zn, cd; m#i#i#i=bi, y, gd; m#v=sb, nb)." Limoges, 1990. http://www.theses.fr/1990LIMO0096.

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L'etude du systeme cuo-bi#2o#3-sb#2o#5 a permis de mettre en evidence, outre quatre composes definis deja signales: bisbo#4, bi#3sbo#7, cusb#2o#6 et cubi#2o#4, un compose defini cu#4sb#2o#9 bixbyite et deux phases non-stchiometriques bi#1#-#xcu#xo#1#,#5#-#x#/#2 sillenite et cu#2#-#2#xbi#3#xsb#2#-#xo#7 pyrochlore. Les substitutions cationiques (la, y, gd-bi; nb-sb) realisees sur la phase prototype mb#1#,#5sb#1#,#5o#7 (m=cu, zn, cd) ont permis d'etudier l'influence des differents cations sur les proprietes cristallochimiques et les proprietes electriques qui en resultent
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Mondelli, Claudia. "Fluctuations, frustration and dilution in the SrCrxGa(12-x)O19 compounds : neutron scattering investigation in a broad dynamical range." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10250.

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Le compose srcr xga 1 2 xo 1 9 (scgo) represente un bon exemple de systeme magnetique a basse dimensionalite et haute fluctuation. Scgo est un antiferromagnetique de type heisenberg avec de fortes interactions entre premiers voisins ( c w 500k) mais sans ordre a grande distance jusqu'a 100 mk. Les proprietes magnetiques de ce systeme sont associees a l'arrangement d'une majorite de spins de l'ion cr 3 + sur un sous-reseau hautement frustre (le pyrochlore slab) presentant un etat fondamental de type liquide de spin fortement degenere, mais avec certaines proprietes des verres de spin. Les momen
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Brown, Sonal. "Vibrational spectra and force field investigation of pyrochlore structure compounds." Thesis, 2004. http://localhost:8080/iit/handle/2074/4218.

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"An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites." Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-10-2284.

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Pyrochlore-type oxides (A2B2O7) and glass-ceramic composites have been investigated for nuclear waste sequestration applications due to the remarkable compositional diversity and structural flexibility of these materials. These properties can enhance the incorporation of radioactive waste elements and resistance to radiation induced structural damage. Radiation induced structural damage can be simulated by bombarding materials using high-energy heavy ions. The study has shown how the metal-oxygen bond covalency, cationic radii ratio (rA/rB), and oxygen vacancies of pyrochlore type oxides affec
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Mani, Rohini. "Investigation Of Transition Metal Oxides Of Perovskite, Pyrochlore And Rutile Structures Towards Realization Of Novel Materials." Thesis, 2009. https://etd.iisc.ac.in/handle/2005/1023.

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Materials chemistry is essentially concerned with the design/synthesis of new solids endowed with functional properties that could be of relevance to today’s materials technology. Among the large variety of solid materials that attract attention, metal oxides continue to contribute significantly to current materials chemistry. A wide variety of oxide materials (based on rocksalt, spinel, corundum, perovskite, garnet, pyrochlore and other structures) and their properties have been investigated over the years. Most of these oxides are derived from the transition metals. Transition metal oxide
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Mani, Rohini. "Investigation Of Transition Metal Oxides Of Perovskite, Pyrochlore And Rutile Structures Towards Realization Of Novel Materials." Thesis, 2009. http://hdl.handle.net/2005/1023.

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Materials chemistry is essentially concerned with the design/synthesis of new solids endowed with functional properties that could be of relevance to today’s materials technology. Among the large variety of solid materials that attract attention, metal oxides continue to contribute significantly to current materials chemistry. A wide variety of oxide materials (based on rocksalt, spinel, corundum, perovskite, garnet, pyrochlore and other structures) and their properties have been investigated over the years. Most of these oxides are derived from the transition metals. Transition metal oxides
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Nino, Juan C. "Fundamental structure-property relationships towards engineering of an integrated NPO capacitor for bismuth pyrochlore systems." 2002. http://www.etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-138/index.html.

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Weng, Sheng-Feng, and 翁聖豐. "Hydrogen production from oxidative steam reforming reaction of ethanol over the catalysts with a pyrochlore structure." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/98923030291783617806.

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博士<br>國立交通大學<br>應用化學系碩博士班<br>101<br>Global warming, a critical topic, draws much attention. H2 is a prospective carrier of energy because of its content of energy per unit mass (i.e., 120.7 kJ/g) is larger than for other fuels; it burns cleanly without emitting pollutants to our environment. H2 produced by ethanol reforming is considered to be a sustainable process. An oxidative steam reforming reaction of ethanol (OSRE) combines the partial oxidation (POR) with steam reforming (SRE) and the water-gas-shift reaction (WGS) to take advantage of the heat generated by total oxidation (TOR). The ex
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CHANDRA, KAILASH. "STRUCTURAL AND MAGNETIC PROPERTIES OF PYROCHLORE STRUCTURED MATERIALS." Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20345.

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This thesis focuses on the investigations of structural and magnetic behavior of pyrochlore structured materials synthesized by standard solid-state method. The two main ideas of my work magnetism and geometric frustration are discussed in this thesis. This work explores the substitution effect at A site and B site of Ho2Ti2O7 pyrochlore on structural and magnetic properties and understands the frustration phenomenon at low temperatures. The pyrochlore structured ceramic A2B2O7 (A and B stand for rare earth elements and transition metal respectively) has fascinated an excessive dea
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Saha, Dipankar. "Towards The Design Of Fuctional Materials : Evaluation Based On Crystal Structure, Photocatalysis And Conductivity Measurements." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2295.

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The thesis entitled “Towards the Design of Functional Materials: Evaluation based on Crystal Structure, Photocatalysis and Conductivity Measurements” consist of six chapters. A short introductory note outlines the basis of designing functional materials, different synthetic procedures, characterization techniques and properties such as photocatalysis and ionic conductivity. Chapter 1 describes the effect of Ti doping on photocatalytic activity in orthorhombic perovskite type LnVO3. All the compounds were synthesized by solid state method. Rietveld refinement with high resolution PXRD reveals
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Saha, Dipankar. "Towards The Design Of Fuctional Materials : Evaluation Based On Crystal Structure, Photocatalysis And Conductivity Measurements." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2295.

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The thesis entitled “Towards the Design of Functional Materials: Evaluation based on Crystal Structure, Photocatalysis and Conductivity Measurements” consist of six chapters. A short introductory note outlines the basis of designing functional materials, different synthetic procedures, characterization techniques and properties such as photocatalysis and ionic conductivity. Chapter 1 describes the effect of Ti doping on photocatalytic activity in orthorhombic perovskite type LnVO3. All the compounds were synthesized by solid state method. Rietveld refinement with high resolution PXRD reveals
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Li, Yangyang. "Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics." Thesis, 2013. http://hdl.handle.net/10754/293689.

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The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering te
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Verma, Pramod Kumar. "First principles study of the structural, electronic, elastic, mechanical, thermal, and vibrational properties in pyrochlores and temperature-dependent phonon properties in pyrochlores and SrTiO3 perovskite." Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4468.

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In this thesis, first-principles density functional theory (DFT) calculations are used to study the structural, electronic, elastic, mechanical, and thermal properties in a series of pyrochlore materials. The vibrational properties in these materials are also studied using density functional perturbation theory. Furthermore, and most importantly, a combination of DFT and many-body Green’s function approach is employed to study the temperature-dependence of the vibrational properties arising from anharmonic interactions in some of the pyrochlore compounds and in tetragonal SrTiO3 perovskite. C
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