Microstructure regulation and failure mechanism study of BaTiO3-based dielectrics for MLCC application

Most widely used dielectrics for MLCC are based on BaTiO3 composition which inevitably shows performance degradation during the application due to the migration of oxygen vacancies (V-(sic)). Here, the BaTiO3, (Ba0.97Ca0.03)TiO3, Ba(Ti0.98Mg0.02)O-3, (Ba0.97Ca0.03)(Ti0.98Mg0.02)O-3, (Ba0.96Ca0.03Dy0.01)(Ti0.98Mg0.02)O-3 ceramics (denoted as BT, BCT, BTM, BCTM and BCDTM, respectively) were prepared by a solid-state reaction method. The core-shell structured grains (similar to 200 nm) featured with 10-20 nm wide shell were observed and contributed to the relatively flat dielectric constant-temperature spectra of BTM, BCTM and BCDTM ceramics. The TSDC study found that the single/mix doping of Ca2+, especially the Mg2+, Mg2+/Ca2+ and Mg2+/Ca2+/Dy3+ could limit the emergence of V-(sic) during the sintering and suppress its long-range migration under the electric-field. Because of this, the highly accelerated lifetimes of the ceramics were increased and the value of BCDTM is 377 times higher than that of BT ceramics. The p-n junction model was built to explain the correlation mechanism between the long-range migration of VO and the significantly increased leakage current of BT-based dielectrics in the late stage of HALT.