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Title: Structural phase transitions and crystal chemistry of the series Ba{sub 2} LnB'O{sub 6} (Ln=lanthanide and B'=Nb{sup 5+} or Sb{sup 5+})

Abstract

The structures of 28 compounds in the two series Ba{sub 2} LnSbO{sub 6} and Ba{sub 2} LnNbO{sub 6} have been examined using synchrotron X-ray and in selected cases neutron powder diffraction at, below and above ambient temperature. The antimonate series is found to undergo a sequence of phase transitions from monoclinic to rhombohedral to cubic symmetry with both decreasing ionic radii of the lanthanides and increasing temperature. Compounds in the series Ba{sub 2} LnNbO{sub 6}, on the other hand, feature an intermediate tetragonal structure instead of the rhombohedral structure exhibited by the antimonates. This difference in symmetry is thought to be caused by {pi}-bonding in the niobates that is absent in the antimonates. The bonding environments of the cations in these compounds have also been examined with overbonding of the lanthanide and niobium cations being caused by the unusually large B-site cations. - Graphical abstract: Lattice parameters versus temperature for Ba{sub 2}NdNbO{sub 6}. The formation of the I4/m tetragonal phase contrasts with the antimonate series where a rhombohedral structure occurs instead. This difference is believed to be caused by the presence of {pi}-bonding present in the niobates but absent in the antimonates.

Authors:
 [1];  [2];  [3]
  1. School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia)
  2. School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia), E-mail: kennedyb@chem.usyd.edu.au
  3. Bragg Institute, ANSTO, Private Mail Bag 1, Menai, NSW 2234 (Australia)
Publication Date:
OSTI Identifier:
21015664
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 2; Other Information: DOI: 10.1016/j.jssc.2006.10.017; PII: S0022-4596(06)00563-9; 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:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AMBIENT TEMPERATURE; ANTIMONATES; ANTIMONY IONS; CUBIC LATTICES; LATTICE PARAMETERS; MONOCLINIC LATTICES; NEUTRON DIFFRACTION; NIOBATES; NIOBIUM IONS; OXIDES; PHASE TRANSFORMATIONS; RARE EARTH COMPOUNDS; SYNCHROTRON RADIATION; TETRAGONAL LATTICES

Citation Formats

Saines, Paul J., Kennedy, Brendan J., and Elcombe, Margaret M. Structural phase transitions and crystal chemistry of the series Ba{sub 2} LnB'O{sub 6} (Ln=lanthanide and B'=Nb{sup 5+} or Sb{sup 5+}). United States: N. p., 2007. Web. doi:10.1016/j.jssc.2006.10.017.
Saines, Paul J., Kennedy, Brendan J., & Elcombe, Margaret M. Structural phase transitions and crystal chemistry of the series Ba{sub 2} LnB'O{sub 6} (Ln=lanthanide and B'=Nb{sup 5+} or Sb{sup 5+}). United States. doi:10.1016/j.jssc.2006.10.017.
Saines, Paul J., Kennedy, Brendan J., and Elcombe, Margaret M. Thu . "Structural phase transitions and crystal chemistry of the series Ba{sub 2} LnB'O{sub 6} (Ln=lanthanide and B'=Nb{sup 5+} or Sb{sup 5+})". United States. doi:10.1016/j.jssc.2006.10.017.
@article{osti_21015664,
title = {Structural phase transitions and crystal chemistry of the series Ba{sub 2} LnB'O{sub 6} (Ln=lanthanide and B'=Nb{sup 5+} or Sb{sup 5+})},
author = {Saines, Paul J. and Kennedy, Brendan J. and Elcombe, Margaret M.},
abstractNote = {The structures of 28 compounds in the two series Ba{sub 2} LnSbO{sub 6} and Ba{sub 2} LnNbO{sub 6} have been examined using synchrotron X-ray and in selected cases neutron powder diffraction at, below and above ambient temperature. The antimonate series is found to undergo a sequence of phase transitions from monoclinic to rhombohedral to cubic symmetry with both decreasing ionic radii of the lanthanides and increasing temperature. Compounds in the series Ba{sub 2} LnNbO{sub 6}, on the other hand, feature an intermediate tetragonal structure instead of the rhombohedral structure exhibited by the antimonates. This difference in symmetry is thought to be caused by {pi}-bonding in the niobates that is absent in the antimonates. The bonding environments of the cations in these compounds have also been examined with overbonding of the lanthanide and niobium cations being caused by the unusually large B-site cations. - Graphical abstract: Lattice parameters versus temperature for Ba{sub 2}NdNbO{sub 6}. The formation of the I4/m tetragonal phase contrasts with the antimonate series where a rhombohedral structure occurs instead. This difference is believed to be caused by the presence of {pi}-bonding present in the niobates but absent in the antimonates.},
doi = {10.1016/j.jssc.2006.10.017},
journal = {Journal of Solid State Chemistry},
number = 2,
volume = 180,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}