Effects of cerium doping on dielectric properties and defect mechanism of barium strontium titanate glass-ceramics

The effect of cerium content on phase evolution, dielectric properties and defect mechanism has been investigated in (Ba,Sr)TiO3 glass-ceramics. Cerium mainly acts as an isovalent dopant in the B-site of ABO3 perovskite structure at low content (1 mol%) and then cerium substitution gradually occurs in the A-site with increasing cerium content. A compensation mechanism related to variation in oxygen vacancy concentration has been identified. When cerium content increased to 2 mol%, the maximum values of dielectric constant and energy storage density were simultaneously achieved. The impedance spectra revealed the highest conductivity. It is due to the increase in the concentration of charge carriers accompanied by the decrease in the activation energy of oxygen vacancy migration. With a further addition of cerium to 3 mol%, the opposite trend was observed. The result is related to the presence of more cation vacancies, which, in turn, limits the diffusion rate of oxygen vacancy.