Effect of La2O3 Concentration on Electrical Properties of Barium Strontium Titanate Glass-Ceramics

Barium strontium titanate glass-ceramics with different La2O3 concentrations have been prepared by a melting-annealing technique. The effect of La2O3 concentration on phase evolution, microstructure and electrical properties of (Ba,Sr)TiO3-Al2O3-SiO2 glass-ceramics has been investigated. The X-ray diffraction results showed the volume fraction of the major perovskite (Ba,Sr)TiO3 crystalline phase increased with increasing La2O3 concentration. In addition, the scanning electron microscopy observations revealed that small amounts of La2O3 could accelerate the growth of crystals. When the La2O3 concentration was increased to 1.5 mol%, the microstructure of these samples displayed nonuniform distribution of the crystals. The dc conductivity measurements showed an increasing temperature dependence of conductivity with La2O3 doping at high temperature range above 400 °C. Impedance spectroscopy analysis indicated that the additive of La2O3 changed the major polarization mechanism to the relaxation polarization and the relaxation time for the La2O3 doped samples was much shorter than the undoped ones. The frequency dependence of dissipation factor curve displayed a peak at the range of 1 to 10 kHz due to the La2O3 addition. And the peak value decreased with increasing La2O3 concentration.