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

BaTiO3 powder synthesized by solid-state and hydrothermal method is the main dielectric material for multilayer ceramic capacitors (MLCCs). The microstructure of BaTiO3 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 BaTiO3 prepared with solid-state (S-BaTiO3) and hydrothermal processes (H-BaTiO3), respectively. Both the S-BaTiO3 and H-BaTiO3 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-BaTiO3, while lots of nano-pore defects (10-20 nm) were observed in the H-BaTiO3 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 × 105 MΩ⋅cm and 1.34 × 105 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 Ti3+ 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 BaTiO3 powder has a beneficial effect in enhancing the reliability of MLCCs.