In ceramic multilayer capacitors (MLCCs) prepared from hydrothermal powders, a fine intra-granular porosity leads to cracks and delamination. The small intra-granular pores segregate as large pores at the inner electrodes, thus leading to "bloating" of the MLCCs, perpendicular to the electrodes. Hydrothermal BaTiO_3 and (Ba,Ca)(Ti,Zr)O_3 powders contain large numbers of hydroxyl groups (-OH) in the oxygen sub-lattice. The protons (H~+) are compensated by vacancies on metal sites. On heating to 500°C the point defects disappear, forming fine intra-granular pores of nanometer size.
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