The effects of solid-state and hydrothermal synthesis methods of BaTiO3 on the reliability of multilayer ceramic capacitors

BaTiO
3
powder synthesized by solid-state and hydrothermal method is the main dielectric material for multilayer ceramic capacitors (MLCCs). The microstructure of BaTiO
3
is highly related to the synthesis process, which imposes significant influence on the dielectric and electrical performance of MLCCs. In this study, a systematic investigation was conducted to compare the properties of MLCCs fabricated with BaTiO
3
prepared with solid-state (S-BaTiO
3
) and hydrothermal processes (H-BaTiO
3
), respectively. Both the S-BaTiO
3
and H-BaTiO
3
powders had an average grain size of 250 nm and exhibited a desired single perovskite phase with high tetragonality of 1.0100 and 1.0097. No apparent defects were detected in the S-BaTiO
3
, while lots of nano-pore defects (10-20 nm) were observed in the H-BaTiO
3
powder. For their corresponding S-MLCC and H-MLCC, the characteristic DC dielectric breakdown strengths were 141.74 kV/mm and 135.94 kV/mm, and the initial insulation resistivities at 150°C with the electric field of 10 V/µm were 1.45 × 10
⁵
MΩ⋅cm and 1.34 × 10
⁵
MΩ⋅cm respectively. S-MLCC exhibited a better performance in the highly accelerated lifetime tests than H-MLCC. The better resistance degradation of S-MLCC was resulted from the lower concentration of Ti
³⁺
ion and less Ni diffusion. Reduced defect concentration improved the activation energy of the grain and grain boundary in S-MLCC. All these results suggest that the solid-state BaTiO
3
powder has a beneficial effect in enhancing the reliability of MLCCs.