Exceptional reliability of MLCCs enabled by defect-engineered BaTiO₃

It has generally been believed that the reliability of BaTiO3-based multilayered ceramic capacitors (MLCCs) is mainly contributed by hydroxyl (OH-), and the contribution of CO32- can be neglected. However, in this work, we demonstrated that the contributions of Ba/Ti ratio and CO32- play important roles in the delivering high reliability for BaTiO3-based MLCCs. The structure and performance of MLCC devices and ceramic chips based on BaTiO3 powders prepared by different approaches were studied. It is found that the intracrystalline pores in ceramics or MLCCs are mainly derived from the decomposition of BaCO3 during sintering, which has been demonstrated by ceramic derived from hydrothermal method powder and its modified powders. The point defects of Ba and Ti vacancies mainly originating from nonstoichiometric Ba/Ti rather than thermally stimulated have substantial influence on the migration of grain boundary that determines the grain size and whether the pores can be annihilated from the bulk material. Particularly, the Ti vacancies have a strong pinning effect and inhibit the migration of grain boundary effectively, due to their shorter migration distance comparing to Ba vacancies. Therefore, the synergetic effect of the second phase BaCO3 and point defects leads to the differences in the structure and performance.