Relevant bibliographies by topics / Tetragonal Tungsten Bronzes (TTB)

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  2. Dissertations / Theses

Academic literature on the topic 'Tetragonal Tungsten Bronzes (TTB)'

Author: Grafiati
Published: 22 June 2023

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Journal articles on the topic "Tetragonal Tungsten Bronzes (TTB)"

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Abdullah, A. M., T. Debnath, C. H. Rüscher, and A. Hussain. "Synthesis and Characterization of Vanadium Substituted Potassium Tungsten Bronzes, KxVyW1-yO3." Journal of Scientific Research 4, no. 2 (2012): 507. http://dx.doi.org/10.3329/jsr.v4i2.9349.

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A series of vanadium substituted potassium hexagonal tungsten bronzes KxVyW1-yO3 (K-HTB) were prepared by conventional solid state method at 800 °C with compositions of x = 0.30 and 0.00 ? y ? 0.15. A mixture of K-HTB and non bronze phases with y ? 0.20 was observed. The proportion of this non bronze phase increases with increasing vanadium content. The non bronze phases in the mixture could not be indexed yet. In contrast, a very small amount of vanadium can be substituted in potassium tetragonal tungsten bronzes (K-TTB) at 800 °C with x = 0.50 and 0.00 ? y ? 0.02, however at 700 °C vanadium
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RAVEAU, B., M. M. BOREL, A. LECLAIRE, and A. GRANDIN. "NIOBIUM PHOSPHATE BRONZES — STRUCTURAL RELATIONSHIPS WITH PURE OCTAHEDRAL OXYGEN TUNGSTEN BRONZES." International Journal of Modern Physics B 07, no. 23n24 (1993): 4109–43. http://dx.doi.org/10.1142/s0217979293003590.

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The phosphate niobium bronzes form a large family of structures characterized by pentagonal or hexagonal tunnels. The host lattices of these oxides, involving a mixed valency of niobium Nb(V)-Nb(IV) are described here. The close relationships with pure octahedral structures, mainly perovskites, hexagonal tungsten bronzes (HTB) and tetragonal tungsten bronzes (TTB), and K 3 Nb 8 O 21 are studied.
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Whittle, Thomas A., Siegbert Schmid, and Christopher J. Howard. "Octahedral tilting in the tungsten bronzes." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 71, no. 3 (2015): 342–48. http://dx.doi.org/10.1107/s2052520615008252.

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Possibilities for `simple' octahedral tilting in the hexagonal and tetragonal tungsten bronzes (HTB and TTB) have been examined, making use of group theory as implemented in the computer programISOTROPY. For HTB, there is one obvious tilting pattern, leading to a structure in space groupP63/mmc. This differs from the space groupP63/mcmfrequently quoted from X-ray studies – these studies have in effect detected only displacements of the W cations from the centres of the WO6octahedra. The correct space group, taking account of both W ion displacement and the octahedral tilting, isP6322 – structu
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Smirnov, M., and P. Saint-Grégoire. "Unified approach for determining tetragonal tungsten bronze crystal structures." Acta Crystallographica Section A Foundations and Advances 70, no. 3 (2014): 283–90. http://dx.doi.org/10.1107/s2053273314003994.

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Tetragonal tungsten bronze (TTB) oxides are one of the most important classes of ferroelectrics. Many of these framework structures undergo ferroelastic transformations related to octahedron tilting deformations. Such tilting deformations are closely related to the rigid unit modes (RUMs). This paper discusses the whole set of RUMs in an ideal TTB lattice and possible crystal structures which can emerge owing to the condensation of some of them. Analysis of available experimental data for the TTB-like niobates lends credence to the obtained theoretical predictions.
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Shakil, Md Mahbubur R., Tapas Debnath, Claus H. Ruscher, and Altaf Hussain. "Study of Tantalum Substituted Potassium Tungsten Bronzes." Journal of the Bangladesh Chemical Society 25, no. 1 (2012): 38–45. http://dx.doi.org/10.3329/jbcs.v25i1.11770.

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A series of compounds KxTayW1-yO3 with x = 0.30, 0.00 ? y ? 0.30 and x = 0.55, 0.00 ? y ? 0.10 were synthesized by conventional solid-state method. The samples were characterized using XRD and FTIR spectroscopy. X-ray powder patterns reveal that the samples with compositions x = 0.30, y ? 0.30 show hexagonal tungsten bronze (HTB) type phase and the samples with x = 0.55, 0.02 ? y ? 0.10 show a mixture of two phases (K-HTB and tetragonal potassium tungsten bronze, K-TTB). The samples of the system, K0.30TayW1-yO3 with 0.00 ? y ? 0.15 shows no significant change in the cell parameters. However,
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Bursill, L. A., J. L. Peng, B. Jiang, and X. Li. "Crystal Structure of Red Lead Titanate Thin Films." Modern Physics Letters B 11, no. 26n27 (1997): 1181–87. http://dx.doi.org/10.1142/s0217984997001419.

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Orange-red lead titanate thin films are examined by high-resolution transmission electron microscopy and diffraction. It is remarkable that the structure is based on that of tetragonal-tungsten-bronze (TTB) rather than perovskite-type. The chemical basis for this result is examined, it is deduced that the TTB structure is stabilized by inclusion of hydroxyl ions during synthesis by a sol–gel route involving hydrolysis of n-Butyl titanate.
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Krumeich, Frank. "On the Arrangement of Pentagonal Columns in Tetragonal Tungsten Bronze-Type Nb18W16O93." Crystals 11, no. 12 (2021): 1514. http://dx.doi.org/10.3390/cryst11121514.

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The evaluation of HAADF-STEM images of a sample with the composition Nb18W16O93 provided new insights into its real structure. The basic structure comprises an intact octahedral framework of the tetragonal tungsten bronze (TTB) type. The partial occupation of the pentagonal tunnels (PT) by metal–oxygen strings determines the oxygen-to-metal ratio (O/ΣM with M = Nb,W). For a large area, the O/ΣM was determined to be 2.755, which is bigger than the value of Nb18W16O93, which is O/ΣM = 2.735. To a large extent, the three-fold TTB superstructure of Nb8W9O47 with a high oxygen content is present (O
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Krumeich, F. "Order and Disorder in Niobium Tungsten Oxides of the Tetragonal Tungsten Bronze Type." Acta Crystallographica Section B Structural Science 54, no. 3 (1998): 240–49. http://dx.doi.org/10.1107/s010876819701971x.

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Two superstructures of the TTB type (tetragonal tungsten bronze) exist in the system Nb2O5/WO3. They are caused by an ordered arrangement of pentagonal tunnels filled with metal–oxygen strings. Besides the well known 4:9 phase (Nb8W9O47), which has a tripled b axis, evidence for a new orthorhombic structure, Nb6W8O39 (a = b = 27.3 Å), has been found. The oxidation products of Nb7W10O47 and Nb4W13O47 frequently comprise less-ordered arrangements of filled tunnels, causing diffuse scattering. In Nb7W10O47.5 the electron diffraction patterns (along [001]) of many crystal fragments show circular d
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Namikuchi, Eliane Ayumi, Marcos Augusto Lima Nobre, and Silvania Lanfredi. "Selective Occupancy of Sites by Rare Earths in K2Nd(1-X)EuxNb5O15 Nanopowders, where X = 0, 0.0025, 0.025, 0.05 and 0.1, Prepared by Modified Polyol Method." Materials Science Forum 820 (June 2015): 361–66. http://dx.doi.org/10.4028/www.scientific.net/msf.820.361.

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Niobates with tetragonal tungsten bronze TTB-type structure have presented great technological potential due to their dielectric, ferroelectric, pyroelectric properties. The preparation by the modified polyol method and structural characterization of K2Nd(1-x)EuxNb5O15 nanopowders, where x = 0; 0.0025; 0.025; 0.05 e 0.1, were investigated. The structural parameters were analyzed as a function of concentration of europium ions in the K2NdNb5O15 host structure using the Rietveld method. From structural parameters was determined the TTB-type structure with tetragonal symmetry, where the pentagona
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Graetsch, Heribert A., Chandra Shehkar Pandey, Jürgen Schreuer, Manfred Burianek, and Manfred Mühlberg. "Incommensurate modulations of relaxor ferroelectric Ca0.24Ba0.76Nb2O6(CBN24) and Ca0.31Ba0.69Nb2O6(CBN31)." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 70, no. 4 (2014): 743–49. http://dx.doi.org/10.1107/s2052520614011676.

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CBN crystals show a one- and a two-dimensionally modulated modification. The former is isotypic with orthorhombic Ba4Na2Nb10O30and the latter with the tetragonal tungsten bronze type of crystal structure. The orthorhombic form irreversibly transforms to the tetragonal polymorph at the ferroelectric phase transition near 603 K. Orthorhombic and tetragonal CBN24 slightly differ in the distribution of the Ba and Ca atoms over the incompletely filled Me1 and Me2 sites. The tetragonal symmetry is further broken in orthorhombic CBN24 by different amplitudes of the positional modulations of O atoms w
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Dissertations / Theses on the topic "Tetragonal Tungsten Bronzes (TTB)"

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Belarbi, Mahfoud. "Préparation et caractérisation des matériaux diélectriques de structure "Bronzes de Tungstène Quadratiques" pour le stockage de l'énergie électrostatique." Electronic Thesis or Diss., Amiens, 2022. http://www.theses.fr/2022AMIE0045.

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Les travaux présentés dans cette thèse concernent l'élaboration et la caractérisation des matériaux diélectriques sans plomb, capables d'emmagasiner directement de l'énergie électrostatique, thermiquement stables et facile à intégrer dans des circuits électriques. Au cours de ce travail, nous nous sommes intéressés à une nouvelle famille de matériaux ferroélectriques de structure de type Bronze oxygéné de tungstène quadratique (TTB). L'intérêt porté à cette famille réside dans le fait que la structure TTB présente trois types de tunnels de section pentagonale, carré et triangulaire, capables d
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Heijboer, Pierre. "Etude des propriétés diélectriques et structurales de monocristaux et céramiques de structure TTB." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0096/document.

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Les travaux présentés dans ce manuscrit concernent des niobates de formulation Ba2LnNb4O15 (Ln = La ou Nd) et de structure "Tetragonal Tungsten Bronze" (TTB). Ces travaux se situent à la charnière de la chimie et de la physique des matériaux diélectriques et visent à mettre en relation structure cristalline et propriétés diélectriques. L'étude a été menée sur des TTB élaborés sous forme céramique et monocristalline. Après détermination de conditions optimales de croissance, par fusion de zone en four à image, des sections monocristallines ont été obtenues et caractérisées. Les résultats obtenu
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Drathen, Christina. "Transition metal fluorides : from superconductors to multiferroics." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/6687.

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Transition metal fluorides represent an important family of complex solids displaying a variety of different properties and interesting phenomena. Despite their remarkable behaviour, these classes of materials have not received much attention and the rationalization of their behaviour is still lacking a systematic approach. This thesis aims to contribute to the field by examining previously unknown or understudied complex fluorides. The compounds were selected for their intriguing physical properties that range from superconductivity to multiferroism. The discovery of superconductivity in the
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Derbazi, Maqboula. "Étude des caractéristiques Raman et optique non-linéaire des bronzes de tungstène quadratiques (A6M2M’8O30)." Thesis, Reims, 2013. http://www.theses.fr/2013REIMS041.

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Des recherches très importantes ont été dédiées à l'étude des composés ferroélectriques de type bronze de tungstène quadratique (TTB). Cette thèse concerne la synthèse et la caractérisation de 7 matériaux TTB de formule générale A6M2M'8O30 (A = Sr2+, Ba2+ ou Pb2+, M = Ti4+, Zr4+ ou HF4+; M' = Nb5+ ou Ta5+). Ces composés cristallins de grande taille ∼100 nm ont été synthétisés sous forme de poudre. Les moyennes expérimentales : diffractions des rayons X, spectroscopie Raman, la microscopie électronique MEB et MET, l'optique non linéaire ONL, ont permis d'établir des relations étroites entre str
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Albino, Marjorie. "Synthèse et caractérisation structurale et diélectrique de céramiques et de monocristaux relaxeurs de structure TTB." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00920357.

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La structure bronze quadratique de tungstène, grâce à sa flexibilité cristallochimique, est une candidate légitime pour le développement de matériaux fonctionnels. L'étude des propriétés diélectriques, pyroélectriques, et ferroélectriques de céramiques de formulation Ba2NdFeNb4-xTaxO15 montre un crossover relaxeur-ferroélectrique-paraélectrique, avec une hystérèse thermique de la transition ferroélectrique. L'étude structurale des monocristaux relaxeurs Ba2LnFeNb4O15 (Ln=La, Pr, Nd, Sm, Eu), obtenus par la méthode du flux, a mis en évidence une structure modulée. L'affinement de la structure d
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Gardner, Jonathan. "Ferroelectricity in empty tetragonal tungsten bronzes." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/10592.

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In this work, in-depth structural and electrical characterisation is used to study a family of “empty” tetragonal tungsten bronzes (TTBs), A2₄A1₂B1₂B2₈O₃₀. An initial investigation into the effect of the A1-cation size on the properties of empty Ba₄R₀.₆₇◻₁.₃₃Nb₁₀O₃₀ TTBs (where R is the A1-cation and R = La, Nd, Sm, Gd, Dy and Y; ◻ = vacancy) was performed. These were determined to be metrically tetragonal by powder x-ray diffraction, with decreasing R cation size inducing increased crystal anisotropy. This tetragonal structural distortion, driven by contraction in the ab-plane, is shown to st
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Castel, Elias. "Synthèse de nouveaux matériaux multiferroïques au sein de la famille des bronzes quadratiques de formule Ba2LnFeNb4O15." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13865/document.

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Les multiferroïques sont des matériaux dans lesquels plusieurs propriétés ferroïques peuvent coexister, e. g. ferromagnétisme et ferroélectricité. La recherche de tels matériaux fait l'objet d'une activité croissante en raison de l’enjeu majeur qu’ils représentent dans de nombreux domaines (mémoires, spintronique…). Les matériaux qui possèdent les propriétés nécessaires pour des applications futures sont cependant peu nombreux. Des niobates de formule Ba2LnFeNb4O15 (Ln = lanthanide), de structure bronze quadratique (TTB) susceptibles de présenter un ordre ferroélectrique et un ordre magnétique
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Ahamad, M. Niyaz. "Multifunctionalities Of Telllurite And Borate Based Glasses Comprising Nano/Micro Crystals Of Tetragonal Tungsten Bronze-Type Ferroelectric Oxides." Thesis, 2009. http://hdl.handle.net/2005/1004.

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Transparent glasses embedded with TTB structured ferroelectric nano/micro crystals (K3Li2Nb5O15, Ba5Li2Ti2Nb8O30) were fabricated in various tellurite and borate based glass matrices and characterized for their physical properties. Nanocrystals of K3Li2Nb5O15 were successfully grown inside tellurite glass matrix via conventional heat-treatment route. Eventhough, tellurite glasses preferentially crystallize only on the surface, bulk uniform crystallization was achieved in the (100-x) TeO2 - x(1.5K2O-Li2O-2.5Nb2O5) system. Heat capacity studies revealed them to be thermodynamically less fragi
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