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Title: New insight into the symmetry and the structure of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=lanthanides and Y)

Abstract

Structures of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, and Y) at room temperature have been re-examined by Rietveld profile analysis of X-ray diffraction data. It was shown that the correct phase sequence across the lanthanides is I2/m (Ln=La, Pr, Nd, and Sm), I4/m (Ln=Eu, Gd, Tb, and Dy), and Fm3-bar m (Ln=Ho and Y), respectively. All phases can be derived from the ideal cubic perovskite by ordering the Ln(III) and Nb(V) ions and by out-of-phase tilting the LnO{sub 6}/NbO{sub 6} octahedra around either the primitive two-fold [110]{sub p}-axis (I2/m) or the four-fold [001]{sub p}-axis (I4/m). The monoclinic P2{sub 1}/n structure that contains both out-of-phase and in-phase tilt around the primitive [110]{sub p}- and [001]{sub p}-axis, respectively, has not been observed for this series of compounds.

Authors:
 [1];  [2]
  1. Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands). E-mail: w.fu@chem.leidenuniv.nl
  2. Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands)
Publication Date:
OSTI Identifier:
20784952
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 179; Journal Issue: 4; Other Information: DOI: 10.1016/j.jssc.2005.12.031; PII: S0022-4596(05)00627-4; Copyright (c) 2005 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; BARIUM COMPOUNDS; CUBIC LATTICES; MONOCLINIC LATTICES; NIOBIUM COMPOUNDS; PEROVSKITE; RARE EARTH COMPOUNDS; TEMPERATURE RANGE 0273-0400 K; TETRAGONAL LATTICES; X-RAY DIFFRACTION

Citation Formats

Fu, W.T., and IJdo, D.J.W.. New insight into the symmetry and the structure of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=lanthanides and Y). United States: N. p., 2006. Web. doi:10.1016/j.jssc.2005.12.031.
Fu, W.T., & IJdo, D.J.W.. New insight into the symmetry and the structure of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=lanthanides and Y). United States. doi:10.1016/j.jssc.2005.12.031.
Fu, W.T., and IJdo, D.J.W.. Sat . "New insight into the symmetry and the structure of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=lanthanides and Y)". United States. doi:10.1016/j.jssc.2005.12.031.
@article{osti_20784952,
title = {New insight into the symmetry and the structure of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=lanthanides and Y)},
author = {Fu, W.T. and IJdo, D.J.W.},
abstractNote = {Structures of the double perovskites Ba{sub 2}LnNbO{sub 6} (Ln=La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, and Y) at room temperature have been re-examined by Rietveld profile analysis of X-ray diffraction data. It was shown that the correct phase sequence across the lanthanides is I2/m (Ln=La, Pr, Nd, and Sm), I4/m (Ln=Eu, Gd, Tb, and Dy), and Fm3-bar m (Ln=Ho and Y), respectively. All phases can be derived from the ideal cubic perovskite by ordering the Ln(III) and Nb(V) ions and by out-of-phase tilting the LnO{sub 6}/NbO{sub 6} octahedra around either the primitive two-fold [110]{sub p}-axis (I2/m) or the four-fold [001]{sub p}-axis (I4/m). The monoclinic P2{sub 1}/n structure that contains both out-of-phase and in-phase tilt around the primitive [110]{sub p}- and [001]{sub p}-axis, respectively, has not been observed for this series of compounds.},
doi = {10.1016/j.jssc.2005.12.031},
journal = {Journal of Solid State Chemistry},
number = 4,
volume = 179,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • The structure of 14 compounds in the series Ba{sub 2}LnTaO{sub 6} have been examined using synchrotron X-ray diffraction and found to undergo a sequence of phase transitions from I2/m monoclinic to I4/m tetragonal to Fm3-bar m cubic symmetry with decreasing ionic radii of the lanthanides. Ba{sub 2}LaTaO{sub 6} is an exception to this with variable temperature neutron diffraction being used to establish that the full series of phases adopted over the range of 15-500 K is P2{sub 1}/n monoclinic to I2/m monoclinic to R3-bar rhombohedral. The chemical environments of these compounds have also been investigated and the overbonding to themore » lanthanide cations is due to the unusually large size for the B-site in these perovskites. - Graphical abstract: The evolution of the structure across the series of double perovskites Ba{sub 2}LnTaO{sub 6} is established using a combination of synchrotron X-ray and neutron diffraction. The symmetry increases from monoclinic to tetragonal and then cubic as the size of the lanthanide decreases.« less
  • Single crystals of double-perovskite type lanthanide magnesium iridium oxides, Ln{sub 2}MgIrO{sub 6} (Ln=Pr, Nd, Sm-Gd) have been grown in a molten potassium hydroxide flux. The compounds crystallize in a distorted 1:1 rock salt lattice, space group P2{sub 1}/n, consisting of corner shared MO{sub 6} (M=Mg{sup 2+} and Ir{sup 4+}) octahedra, where the rare earth cations occupy the eight-fold coordination sites formed by the corner shared octahedra. Pr{sub 2}MgIrO{sub 6}, Nd{sub 2}MgIrO{sub 6}, Sm{sub 2}MgIrO{sub 6}, and Eu{sub 2}MgIrO{sub 6} order antiferromagnetically around 10-15 K. - Graphical abstract: A SEM image of a typical crystal of Ln{sub 2}MgIrO{sub 6}, which formsmore » in the monoclinic double perovskite structure, is shown.« less
  • The crystal structures of Ba{sub 2}LnSbO{sub 6} (Ln=La, Pr, Nd and Sm) at room temperature have been investigated by profile analysis of the Rietveld method using either combined X-ray and neutron powder diffraction data or X-ray powder diffraction data. It has been shown that the structure of Ba{sub 2}LnSbO{sub 6} with Ln =La, Pr and Nd are neither monoclinic nor cubic as were previously reported. They are rhombohedral with the space group R3-bar . The distortion from cubic symmetry is due to the rotation of the LnO{sub 6}/SbO{sub 6} octahedra about the primitive cubic [111]{sub p}-axis. On the other hand,more » the structure of Ba{sub 2}SmSbO{sub 6} is found to be cubic. All compounds contain an ordered arrangement of LnO{sub 6} and SbO{sub 6} octahedra.« less
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