Strontium and calcium pyroniobates were prepared by a sol–gel process, using strontium/calcium metal and niobium ethoxide as precursors. The formation of Sr 2 Nb 2 O 7 occurred at 750°C via an intermediate perovskite phase of composition close to Sr 0.82 NbO 3 . The crystallization of Ca 2 Nb 2 O 7 occurred at 600°C directly without any intermediate phases. Sintered Sr 2 Nb 2 O 7 and Ca 2 Nb 2 O 7 pellets showed a preferred grain orientation. Microstructural studies revealed an increase in grain growth and associated orientation with sintering temperature.
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Prasadarao et al. (1992) studied this question.
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