Effect of SiO2 on dielectric properties of core-shell Sr and Tm co-doped BaTiO3@SiO2 ceramics

Sr and Tm co-doped Ba0.7Sr0.3Ti0.9925Tm0.01O3 (BST) and core-shell structured BST@SiO2 ceramics were prepared by sol-gel method and conventional sintering. Along with the obvious perovskite phases in the BST and BST@SiO2 powders, a new phase, Ba2TiSi2O8, was confirmed in the sintered BST@SiO2 bulk by XRD analysis. TEM analysis revealed that the BST powders were coated with an amorphous SiO2 film, while SEM analysis indicated that the SiO2 film plays a role in grain size reduction. The dielectric losses of BST@SiO2 ceramics reduced effectively compared to that of BST. In addition, the Curie peak of the BST@1%SiO2 ceramic significantly broadened and the Curie temperature shifted toward lower temperatures; this provides a new approach to improving the dielectric properties of BaTiO3 ceramics.