Structures and crystal chemistry of the double perovskites Ba{sub 2}LnB'O{sub 6} (Ln=lanthanide and B'=Nb, Ta):

Journal Article · Thu Nov 15 04:00:00 EST 2007 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2007.08.010· OSTI ID:21043719

Saines, Paul J; Spencer, Jarrah R ^[1]; Kubota, Yoshiki; Minakata, Chiharu; Hano, Hiroko ^[2]; Kato, Kenichi; Takata, Masaki ^[3]

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1. School of Chemistry, University of Sydney, Sydney, NSW 2006 (Australia)
2. Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)
3. RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

The structures of eight members of the series of double perovskites of the type Ba{sub 2}LnB'O{sub 6} (Ln=La{sup 3+}-Sm{sup 3+} and Y{sup 3+} and B'=Nb{sup 5+} and Ta{sup 5+}) were examined both above and below room temperature using synchrotron X-ray powder diffraction. The La{sup 3+} and Pr{sup 3+} containing compounds had an intermediate rhombohedral phase whereas the other tantalates and niobates studied have a tetragonal intermediate. This difference in symmetry appears to be a consequence of the larger size of the La{sup 3+} and Pr{sup 3+} cations compared to the other lanthanides. The temperature range over which the intermediate symmetry is stable is reduced in those compounds near the point where the preferred intermediate symmetry changes from tetragonal to rhombohedral. In such compounds the transition to the cubic phase involves higher order terms in the Landau expression. This suggests that in this region the stability of the two intermediate phases is similar. - Graphical abstract: Variable temperature structural studies of Ba{sub 2}LaTaO{sub 6} show the presence of a unexpected rhombohedral phase. Other Ba{sub 2}LnB'O{sub 6} (B'=Nb, Ta) have a tetragonal intermediate phase.

• OSTI ID: 21043719
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 11 Vol. 180; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
BARIUM COMPOUNDS
CRYSTALS
LANTHANUM IONS
NEUTRON DIFFRACTION
NIOBATES
NIOBIUM IONS
PEROVSKITE
PHASE TRANSFORMATIONS
PRASEODYMIUM IONS
SAMARIUM COMPOUNDS
SAMARIUM IONS
SYNCHROTRONS
TANTALATES
TANTALUM IONS
TEMPERATURE RANGE 0273-0400 K
X-RAY DIFFRACTION
YTTRIUM COMPOUNDS
YTTRIUM IONS