Doping behaviors of yttrium, zinc and gallium in BaTiO3 ceramics for AC capacitor application

The doping behaviors of yttrium, zinc and gallium and their effects on the dielectric properties and microstructures of BaTiO3 were investigated. Y3+ dissolved in the lattice of BaTiO3, replacing both Ba2+ site and Ti4+ site; while Zn2+ and Ga3+ tended to occupy Ti4+ site. Compared with Y2O3 and Ga2O3, ZnO suppressed grain growth of BaTiO3 more effectively and promoted greater uniformity of grains, thus reducing the dielectric loss. The addition of Ga2O3 inhibited the appearance of second phase Y2Ti2O7 and enhanced the sinterability, which was ascribed to the compensation mechanism and synergistic effect. Proper amount of Y2O3, Ga2O3 and ZnO significantly improved the dielectric temperature characteristics due to the formation of the core-shell structure in the codoped BaTiO3 ceramics. High performance dielectrics with epsilon(r) of 2,690, tan delta of 1.0 % (at 1 kHz), and alternating current breakdown voltage E > 3.73 kV/mm, were achieved.