Electrical properties and degradation behavior of Tm2O3 doped barium titanate ceramics for MLCCs

The doping effect of thulium on electrical properties and degradation behavior in barium titanate ceramics (BaTiO3) was investigated in terms of generations of core-shell structure and micro-chemical changes through highly accelerated degradation test. The dielectric specimens of pellet type and multi-layered sheets were prepared by using BaTiO3 with undoped and doped with 1 mol% Tm2O3. The BaTiO3 ceramics doped with 1 mol% Tm2O3, had 40 % higher dielectric constant (epsilon = 2700) than that of the undoped BaTiO3 specimen at curie temperature and met X7R specification. According to the result of highly accelerated degradation test conducted at 150 degrees C, 70 V, and 24 hr, the oxygen diffusion was declined in dielectrics doped with I mol% Tm2O3. The Tm3+ ion substituted selectively Ba site and Ti site and contributed to the generation of the core-shell structure. Oxygen vacancies occurred by substitution for Ti site could reduce excess oxygen that reacted to the Ni electrode.