Investigation of the sintering of barium titanate ceramics by oxygen coulometry

The oxygen coulometry method by solid electrolyte circonia cells was applied to investigate the sintering process of Ba1–xLaxTiO3 ceramics (0⩽x⩽0.05). During the heating, three different oxygen release phenomena were observed: (1) the O2 release due to the formation of Schottky-type oxygen vacancies; (2) the O2 release caused by the incorporation of the donor impurity during grain growth; and (3) an irreversible oxygen release with an onset temperature between 1000 and 1150°C, for which the cause is not clear. The quantitative data of the effect (2) can be explained on condition that the donors are charge compensated both by electrons and by cation vacancies.