Phase segregation in mixed Nb–Sb double perovskites Ba2LnNb1−xSbxO6
✍ Scribed by Paul J. Saines; Brendan J. Kennedy
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 949 KB
- Volume
- 181
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The phase composition of two series of mixed Nb 5+ -Sb 5+ double perovskites formed between the pairs Ba 2 EuNbO 6 -Ba 2 PrSbO 6 and Ba 2 NdSbO 6 -Ba 2 NdNbO 6 have been studied using synchrotron X-ray powder diffraction methods. In both series extensive phase segregation is observed demonstrating limited solubility of Sb 5+ in these Nb 5+ perovskites, irrespective of the precise structures of the double perovskite. Evidence for a monoclinic I2/m phase in the series formed between tetragonal I4/m Ba 2 EuNbO 6 and rhombohedral R 3 Ba 2 EuNbO 6 is presented. It is postulated that this phase segregation is a consequence of competing bonding requirements of the Nb 5+ and Sb 5+ cations associated with their electronic configurations.