Abstract
Pyrochlore type precursor with nominal composition of Sn2Ta2O7 was oxidized in O2 at various temperatures for 5 h. The precursor phase was hardly oxidized below 573 K. The precursor was oxidized, but decomposed into SnO2 and Ta2O5 mixture above 873K. For intermediate temperatures between 673K and773 K, novel metastable phase with nominal composition of SnTaO4+x was appeared. Sn and Ta ions in the metastable phase are in an ordered arrangement similar to the arrangement in pyrochlore type precursor. It was inferred that the metastable phase was formed by cation diffusionless insertion of oxygen atoms into the original vacant oxygen site of pyrochlore structure during the oxidation. Composition of the novel metastable phase has been determined by ICP and TG analysis together with composition of pyrochlore type precursor.
