Composition- and temperature-dependent phase transitions in 1:3 ordered perovskites Ba{sub 4-x}Sr{sub x}NaSb{sub 3}O{sub 12}

A series of 25 members of the 1:3 ordered perovskite family of the type Ba{sub 4-x}Sr{sub x}NaSb{sub 3}O{sub 12} has been synthesized and their structures determined using synchrotron X-ray and neutron powder diffraction techniques. At room temperature the sample Ba{sub 4}NaSb{sub 3}O{sub 12} has a...

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Bibliographic Details
Published in:Journal of solid state chemistry 2007-11, Vol.180 (11)
Main Authors: Zhou Qingdi, Kennedy, Brendan J., Elcombe, Margaret M., Withers, Ray L.
Format: Article
Language:English
Subjects:
ANTIMONY COMPOUNDS
BARIUM COMPOUNDS
CATIONS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
MONOCLINIC LATTICES
NEUTRON DIFFRACTION
ORTHORHOMBIC LATTICES
PEROVSKITE
PHASE TRANSFORMATIONS
SODIUM COMPOUNDS
SPACE GROUPS
STRONTIUM COMPOUNDS
SYMMETRY
SYNCHROTRONS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TETRAGONAL LATTICES
X-RAY DIFFRACTION
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Summary:A series of 25 members of the 1:3 ordered perovskite family of the type Ba{sub 4-x}Sr{sub x}NaSb{sub 3}O{sub 12} has been synthesized and their structures determined using synchrotron X-ray and neutron powder diffraction techniques. At room temperature the sample Ba{sub 4}NaSb{sub 3}O{sub 12} has a cubic structure in space group Im3-bar m with a=8.2821(1) A, where the Na and Sb cations are ordered in the octahedral sites but there is no tilting of the (Na/Sb)O{sub 6} octahedra. As the average size of the A-site cation decreases, through the progressive replacement of Ba by Sr, tilting of the octahedra is introduced firstly lowering the symmetry to tetragonal in P4/mnc then to orthorhombic in Cmca and ultimately a monoclinic structure in P2{sub 1}/n as seen for Sr{sub 4}NaSb{sub 3}O{sub 12} with a=8.0960(2) A, b=8.0926(2) A, c=8.1003(1) A and {beta}=90.016(2) deg. The powder neutron diffraction studies show that the orthorhombic and tetragonal phases in Cmca and P4/mnc co-exist at room temperature for samples with x between 1.5 and 2. - Graphical abstract: Diffraction studies of the series of A{sub 4}NaSb{sub 3}O{sub 12} perovskites revel a complex series of temperature- and composition-dependent phase transitions, associated with both ordering of the Na and Sb cations and tilting of the octahedra.
ISSN:0022-4596
1095-726X
DOI:10.1016/j.jssc.2007.09.004