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Title: 6H hexagonal structure of low loss Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) dielectrics

Abstract

The crystal structure of Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) oxides has been found to be 6H hexagonal, space group P6{sub 3}/mmc, parameters of unit cell: a = 5.7943(1) A, c = 14.1642(1) A and a = 5.7993(1) A, c = 14.1626(1) A for M = Mg and Zn, respectively. The tungsten and titanium atoms are randomly distributed in pairs of face-sharing octahedra separated by octahedral layers containing magnesium or zinc. It was revealed that the structures are well ordered which is believed to result in a low dielectric loss at a microwave frequency reported for these materials.

Authors:
 [1];  [2];  [2]
  1. Department of Ceramics and Glass Engineering/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal). E-mail: dkhalyavin@cv.ua.pt
  2. Department of Ceramics and Glass Engineering/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)
Publication Date:
OSTI Identifier:
20900951
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 42; Journal Issue: 1; Other Information: DOI: 10.1016/j.materresbull.2006.05.005; PII: S0025-5408(06)00202-9; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BARIUM OXIDES; DIELECTRIC MATERIALS; HCP LATTICES; LAYERS; MAGNESIUM; MICROWAVE RADIATION; OXIDES; SPACE GROUPS; TITANIUM; TUNGSTEN; X-RAY DIFFRACTION; ZINC

Citation Formats

Khalyavin, D.D., Senos, A.M.R., and Mantas, P.Q. 6H hexagonal structure of low loss Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) dielectrics. United States: N. p., 2007. Web. doi:10.1016/j.materresbull.2006.05.005.
Khalyavin, D.D., Senos, A.M.R., & Mantas, P.Q. 6H hexagonal structure of low loss Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) dielectrics. United States. doi:10.1016/j.materresbull.2006.05.005.
Khalyavin, D.D., Senos, A.M.R., and Mantas, P.Q. Thu . "6H hexagonal structure of low loss Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) dielectrics". United States. doi:10.1016/j.materresbull.2006.05.005.
@article{osti_20900951,
title = {6H hexagonal structure of low loss Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) dielectrics},
author = {Khalyavin, D.D. and Senos, A.M.R. and Mantas, P.Q.},
abstractNote = {The crystal structure of Ba{sub 3}MTiWO{sub 9} (M = Mg, Zn) oxides has been found to be 6H hexagonal, space group P6{sub 3}/mmc, parameters of unit cell: a = 5.7943(1) A, c = 14.1642(1) A and a = 5.7993(1) A, c = 14.1626(1) A for M = Mg and Zn, respectively. The tungsten and titanium atoms are randomly distributed in pairs of face-sharing octahedra separated by octahedral layers containing magnesium or zinc. It was revealed that the structures are well ordered which is believed to result in a low dielectric loss at a microwave frequency reported for these materials.},
doi = {10.1016/j.materresbull.2006.05.005},
journal = {Materials Research Bulletin},
number = 1,
volume = 42,
place = {United States},
year = {Thu Jan 18 00:00:00 EST 2007},
month = {Thu Jan 18 00:00:00 EST 2007}
}
  • The 6H perovskites Ba{sub 3}MSb{sub 2}O{sub 9} (M = Mg, Ni, Zn) have been subjected to pressures of up to 5.5 GPa. No structural phase transitions were observed in Ba{sub 3}MgSb{sub 2}O{sub 9}. Ba{sub 3}NiSb{sub 2}O{sub 9} transformed from a phase containing Sb{sub 2}O{sub 9} dimers formed by face-sharing octahedra into a phase containing NiSbO{sub 9} dimers. This was confirmed by a combination of x-ray powder diffraction and EXAFS. Ba{sub 3}ZnSb{sub 2}O{sub 9} transformed into a cubic perovskite with a partial ordering of zinc and antimony over the octahedral sites.
  • Crystal structures and magnetic properties of quaternary oxides Ba{sub 3}MIr{sub 2}O{sub 9} (M=Mg, Ca, Sc, Ti, Zn, Sr, Zr, Cd and In) were investigated. Rietveld analyses of their X-ray diffraction data indicate that they adopt the 6H-perovskite-type structure with space group P6{sub 3}/mmc or, in the case of M=Ca, Sr and Cd, a monoclinically distorted structure with space group C2/c. The Ir valence configurations are Ba{sub 3}M{sup 2+}Ir{sub 2}{sup 5+}O{sub 9} (M=Mg, Ca, Zn, Sr and Cd), Ba{sub 3}M{sup 3+}Ir{sub 2}{sup 4.5+}O{sub 9} (M=Sc and In) and Ba{sub 3}M{sup 4+}Ir{sub 2}{sup 4+}O{sub 9} (M=Ti and Zr). Magnetic susceptibility and specificmore » heat measurements were carried out. In the Ba{sub 3}M{sup 2+}Ir{sub 2}{sup 5+}O{sub 9}, the Ir{sup 5+} ions have a non-magnetic ground state and the magnetic behavior for these compounds is explained by the Kotani's theory. For Ba{sub 3}M{sup 4+}Ir{sub 2}{sup 4+}O{sub 9}, the effective magnetic moment of these compounds is significantly small, although the Ir{sup 4+} ions have magnetic moment, which indicates the existence of the strong antiferromagnetic interaction between Ir{sup 4+} ions in the Ir{sup 4+}{sub 2}O{sub 9} face-shared bioctahedra. In the case of Ba{sub 3}M{sup 3+}Ir{sub 2}{sup 4.5+}O{sub 9}, a specific heat anomaly was found at about 10K (M=Sc) and 1.6K (M=In), which suggests the magnetic ordering of the magnetic moments of Ir{sup 4+} in the (Ir{sup 4+}Ir{sup 5+})O{sub 9} bioctahedra.« less
  • Millimeter sized crystals of six oxides of approximate composition Ba{sub 4}M{sub z}Pt{sub 3-z}O{sub 9} (M=Co, Ni, Cu, Zn, Mg, Pt) were grown from molten K{sub 2}CO{sub 3} fluxes and found to crystallize in a 2H hexagonal perovskite-related structure type. The compositions of these incommensurate structures, which belong to the A{sub 3n+3m}A′{sub n}B{sub 3m+n}O{sub 9m+6n} family of 2H hexagonal perovskite related oxides, were characterized by X-ray diffraction, energy dispersive spectroscopy, and magnetic susceptibility measurements. The specific synthetic considerations, crystal growth conditions, and magnetic susceptibility measurements are discussed. - Graphical abstract: SEM image and average commensurate unit cell of Ba{sub 4}Pt{sub 3}O{submore » 9.} - Highlights: • Single crystals of the series Ba{sub 4}A′{sub z}Pt{sub 3-z}O{sub 9} were grown via a molten carbonate flux. • Ba{sub 4}Pt{sub 3}O{sub 9} and all substitutional variants are incommensurate, composite structures. • All compounds have an approximate stoichiometry of Ba{sub 4}A′Pt{sub 2}O{sub 9.}.« less
  • According to cluster calculations, the electronic structures of compounds based on Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} and Y{sub 1}Ba{sub 2}Cu{sub 4}O{sub 8} with isoelectronically substituted barium have some qualitative distinctions. These compounds behave differently upon barium substitution by other elements due to differences in the character of their highest occupied and lowest unoccupied molecular orbitals. Substitution of barium by radium is expected to lead to an increase in oxygen stability without a significant decrease in the critical temperature of superconduction transition T{sub s}. In order to raise T{sub s}, it is of interest to study the systems YBa{sub 2-m}(Be ormore » Mg){sub m}Cu{sub 3}O{sub x} and YBa{sub 2-m}(Ca, Sr){sub m}Cu{sub 3}O{sub x}. On partial substitution of barium by calcium in YBa{sub 2}Cu{sub 4}O{sub 8}, the mechanism of T{sub s} elevation may involve contraction of the forbidden band due to oxygen sublattice distortions in the vicinity of Ba centers.« less