Synthesis, structures, and phase transitions of barium bismuth iridium oxide perovskites Ba{sub 2}BiIrO{sub 6} and Ba{sub 3}BiIr{sub 2}O{sub 9}

Journal Article · Mon Mar 15 00:00:00 EDT 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2010.01.017· OSTI ID:21372546

Kennedy, Brendan J; Qingdi, Zhou ^[1]; Spencer, Jarrah R ^[2]; Avdeev, Maxim ^[3]

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1. School of Chemistry, University of Sydney, Sydney 2006 (Australia)
2. Department of Pharmacology, University of Sydney, Sydney 2006 (Australia)
3. Bragg Institute, ANSTO, PMB 1, Menai 2234 (Australia)

The Ba-Bi-Ir-O system is found to contain two distinct perovskite-type phases: a rock-salt ordered double perovskite Ba{sub 2}BiIrO{sub 6}; and a 6H-type hexagonal perovskite Ba{sub 3}BiIr{sub 2}O{sub 9}. Ba{sub 2}BiIrO{sub 6} undergoes a series of symmetry-lowering phase transitions on cooling Fm3-barm->R3-barc->12/m(C2/m)->I1-bar(P1-bar), all of which are second order except the rhombohedral->monoclinic one, which is first order. The monoclinic phase is only observed in a 2-phase rhombohedral+monoclinic regime. The transition and 2-phase region lie very close to 300 K, making the room-temperature X-ray diffraction patterns extremely complex and potentially explaining why Ba{sub 2}BiIrO{sub 6} had not previously been identified and reported. A solid solution Ba{sub 2}Bi{sub 1+x}Ir{sub 1-x}O{sub 6}, analogous to Ba{sub 2}Bi{sub 1+x}Ru{sub 1-x}O{sub 6}, 0<=x<=2/3, was not observed. The 6H-type phase Ba{sub 3}BiIr{sub 2}O{sub 9} undergoes a clean second-order phase transition P6{sub 3}/mmc->C2/c at 750 K, unlike 6H-type Ba{sub 3}LaIr{sub 2}O{sub 9}, the P6{sub 3}/mmc structure of which is highly strained below {approx}750 K but fails to distort coherently to the monoclinic phase. - Graphical abstract: Structure of Ba{sub 3}BiIr{sub 2}O{sub 9} at 300 K. BiO{sub 6} octahedra are purple, IrO{sub 6} octahedra are gold, and Ba atoms are green. Thermal ellipsoids at 90% probability.

• OSTI ID: 21372546
• Journal Information: Journal of Solid State Chemistry, Vol. 183, Issue 3; Other Information: DOI: 10.1016/j.jssc.2010.01.017; PII: S0022-4596(10)00031-9; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM COMPOUNDS
BISMUTH COMPOUNDS
HCP LATTICES
IRIDIUM OXIDES
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
PEROVSKITE
PHASE TRANSFORMATIONS
SOLID SOLUTIONS
SYNTHESIS
TEMPERATURE RANGE 0273-0400 K
TRIGONAL LATTICES
X-RAY DIFFRACTION
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
DISPERSIONS
HEXAGONAL LATTICES
HOMOGENEOUS MIXTURES
IRIDIUM COMPOUNDS
MINERALS
MIXTURES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITES
REFRACTORY METAL COMPOUNDS
SCATTERING
SOLUTIONS
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS