Structures and crystal chemistry of the double perovskites Ba{sub 2}LnB'O{sub 6} (Ln=lanthanide B'=Nb{sup 5+} and Ta{sup 5+}): Part I. Investigation of Ba{sub 2}LnTaO{sub 6} using synchrotron X-ray and neutron powder diffraction

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

DOI:https://doi.org/10.1016/j.jssc.2007.08.009· OSTI ID:21043718

Saines, Paul J; Spencer, Jarrah R ^[1]; Avdeev, Maxim ^[2]

---

1. School of Chemistry, University of Sydney, Sydney, New South Wales 2006 (Australia)
2. Bragg Institute, ANSTO, Private Mail Bag 1, Menai, New South Wales 2234 (Australia)

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 the 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.

• OSTI ID: 21043718
• 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
CATIONS
CRYSTALS
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
NEUTRON TEMPERATURE
NIOBATES
NIOBIUM IONS
PEROVSKITE
PHASE TRANSFORMATIONS
RARE EARTH COMPOUNDS
SYMMETRY
SYNCHROTRONS
TANTALATES
TANTALUM IONS
TETRAGONAL LATTICES
X RADIATION
X-RAY DIFFRACTION