The microstructure and dielectric properties of Yb2O3 doped 0.92BaTiO3-0.08(Na0.5Bi0.5)TiO3 relaxor ceramics

The dielectric properties and mechanism of xYb2O3 doped 0.92BaTiO3 - 0.08(Na0.5Bi0.5)TiO3 ceramics with x = 0.005-0.025 have been investigated. The addition of 0.015 mol Yb2O3 improves the permittivity and enhance diffuseness of temperature dependent permittivity for 0.92BaTiO3 - 0.08(Na0.5Bi0.5)TiO3, which gives an epsilon r ' variation within +/- 10 % in 20-170 degrees C. Core-shell microstructures observed in the grains of samples, which is responsible for the dielectric diffuseness and permittivity of xYb2O3 doped 0.92BaTiO3 - 0.08(Na0.5Bi0.5)TiO3 ceramics. Three different relaxation responses are identified by the impedance analysis as grain boundary, grain shell and grain core responses from the low to high frequency. The Yb2O3 shows neglectable effect to the grain boundary but affects the grain shell and grain core obviously. The Yb3+ are mainly in grain shells as x < 0.015 and distributed both in the grain shell and core region as x >= 0.015.