Synthesis and Thermodynamic Stability of Ba2B′B″O6 and Ba3B*B″2O9 Perovskites Using the Molten Salt Method

✍ Scribed by Wei Meng; Anil V. Virkar

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 154 KB
• Volume: 148
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8485

✦ Synopsis

B ‫؍‬ Nb and B* ‫؍‬ Ca were synthesized by a conventional calcination process, as well as by the molten salt method. The former consists of calcining appropriate mixtures of oxide or carbonate precursors in air at elevated temperatures (&12503 3C). The latter method consists of adding appropriate mixtures of oxide or carbonate precursors to a molten salt bath at relatively low temperatures (on the order of 300 to 5003 3C) so that the requisite compound is formed by dissolution+reprecipitation. X-ray di4raction con5rmed the formation of a singlephase perovskite in each case with calcination at 12503 3C. In a molten salt bath, however, all except Ba 2 LaNbO 6 and Ba 2 NdNbO 6 formed the perovskite structure. On the contrary, powders of Ba 2 LaNbO 6 and Ba 2 NdNbO 6 formed by a hightemperature calcination process readily decomposed when introduced into the molten salt bath. The formation of the requisite perovskite at a temperature as low as 3503 3C in a molten salt suggests that: (a) The perovskite is stable at 3503 3C. (b) The molten salt exhibits su7cient precursor solubility for the dissolu-tion+reprecipitation process to occur in a reasonable time. Similarly, the decomposition of Ba 2 LaNbO 6 and Ba 2 NdNbO 6 in a molten salt bath shows that these materials are thermodynamically unstable at the temperature of the molten salt bath.