Sol–Gel Synthesis of Strontium Pyroniobate and Calcium Pyroniobate

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.