Hydrothermal powders of BaTiO 3 and (Ba,Ca)(Ti,Zr)O 3 contain large amounts of protons in the oxygen sublattice. The proton defects are compensated by vacancies on metal sites. When the powder is annealed, water is released and the point defects disappear in the temperature range of 100°-600°C. Metal and oxygen vacancies combine to small nanometer-sized intragranular pores. At temperatures of >800°C, the intragranular pores migrate to the grain boundaries and disappear. In multilayer ceramic capacitors that have been prepared from hydrothermal powders, the intragranular pores are preferentially collected at the inner electrodes, which results in "bloating," cracks, and delamination.

BaTiO 3 and Ba(Ti,Zr)O 3 dielectric powders have been prepared from submicrometer BaCO 3 , TiO 2 , and ZrO 2 . By use of submicrometer BaCO 3 the intermediate formation of Ba 2 TiO 4 second phase can be widely suppressed. Monophase perovskites of BaTiO 3 were already formed at 900°C and Ba-(Ti,Zr)O 3 at 1050°C. Aggregates of very small subgrains could be easily disintegrated to particle sizes <0.5 m.

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