Crystal structures and cation ordering of Sr{sub 2}AlSbO{sub 6} and Sr{sub 2}CoSbO{sub 6}

Journal Article · Fri Aug 15 00:00:00 EDT 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.03.029· OSTI ID:21128371

Faik, A ^[1]; Gateshki, M ^[2]; Pizarro, J L ^[3]; Insausti, M ^[4]; Kaindl, R ^[5]; Grzechnik, A ^[6]

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1. Fisika Aplikatua II Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, P.O. Box 644, Bilbao 48080 (Spain)
2. Australian Nuclear Science and Technology Organization, Private Mail Bag 1, Menai, NSW 2234 (Australia)
3. Departamento de Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, UPV/EHU, PB 644, Bilbao 48080 (Spain)
4. Departamento de Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Apartado 644, E-48080 Bilbao (Spain)
5. Institute of Mineralogy and Petrology, University of Innsbruck, A-6020 Innsbruck (Austria)
6. Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, UPV/EHU, PB 644, Bilbao 48080 (Spain)

The two double perovskite oxides Sr{sub 2}AlSbO{sub 6} and Sr{sub 2}CoSbO{sub 6} were prepared and their structures studied with the X-ray powder diffraction method. At room temperature the crystal structure of Sr{sub 2}AlSbO{sub 6} is cubic (Fm3-barm), with a=5.6058(1)A. It was found that depending on the preparation conditions, the Al{sup 3+} and Sb{sup 5+} cations can be either entirely or partially ordered. In the case of the partially ordered Sr{sub 2}AlSbO{sub 6} sample, the extension of cation ordering was estimated from the hkl-dependent broadening of the diffraction peaks and the results were interpreted as evidence of the formation of anti-phase domains in the material. Low-temperature Raman spectroscopic measurements demonstrated that the cubic phase of Sr{sub 2}AlSbO{sub 6} is stable down to 79 K. The room-temperature crystal structure of Sr{sub 2}CoSbO{sub 6} is trigonal (space group R3-bar) with a=5.6058(1)A and c=13.6758(3)A. At 470 K, however, the material undergoes a continuous phase transition and its structure is converted to cubic (space group Fm3{sup -}barm). The studied Sr{sub 2}CoSbO{sub 6} sample was partially ordered, but unlike Sr{sub 2}AlSbO{sub 6}, no indication of the formation of anti-phase domains was observed. - Williamson-Hall plot of the diffraction peaks in Sr2AlSbO6, samples 1 and 2, and in Sr{sub 2}CoSbO{sub 6}. {beta} denotes the integral breadth corrected for instrumental effects, {theta} is the diffraction angle. It can be seen that in the case of sample 1, {beta} of the superstructure reflections (solid squares) are clearly larger than those of the rest of the peaks. It was found that depending on the preparation conditions, the Al{sup 3+} and Sb{sup 5+} cations can be either entirely or partially ordered. In the case of the partially ordered Sr{sub 2}AlSbO{sub 6} sample, the extension of cation ordering was estimated from the hkl-dependent broadening of the diffraction peaks and the results were interpreted as evidence of the formation of anti-phase domains in the material. In the case of Sr{sub 2}CoSbO{sub 6}, despite the high synthesis temperature (1770 K), the degree of ordering is relatively low. This can be explained by the small difference between the radii of the B-site cations. Another interesting fact is that the sample-related broadening of the diffraction peaks of Sr{sub 2}CoSbO{sub 6} does not show any significant hkl-dependence. This suggests that no extended anti-phase boundaries are formed within the crystallites and the observed low degree of ordering is caused by randomly distributed anti-site defects. In the case of trigonal perovskites the effect of the cation ordering on the peak widths cannot be visualized easily as in the case of cubic perovskites due to the overlapping of the order-related reflections with sub-cell reflections.

• OSTI ID: 21128371
• Journal Information: Journal of Solid State Chemistry, Vol. 181, Issue 8; Other Information: DOI: 10.1016/j.jssc.2008.03.029; PII: S0022-4596(08)00132-1; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM COMPOUNDS
ALUMINIUM IONS
ANTIMONY COMPOUNDS
ANTIMONY IONS
CATIONS
CUBIC LATTICES
OXIDES
PEROVSKITE
PHASE TRANSFORMATIONS
SOLIDS
SPACE GROUPS
STRONTIUM COMPOUNDS
SYNTHESIS
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
TRIGONAL LATTICES
X-RAY DIFFRACTION