Effects of Y2O3 addition on electrical conductivity and dielectric properties of Ba-excess BaTiO3

BaTiO3 + x(BaO + 0.5Y2O3) (x = 0.0-0.03) was prepared by blending BaTiO3 with barium carbonate and yttria, followed by calcination at 1000 C, grinding, pressing and sintering at 1300 C in air. The electrical conductivity was measured at 1100 C as a function of pO2. Microstructures were studied by SEM and XRD, and the temperature coefficient of capacitance was determined over the temperature range -55 to 150 C, at 1 kHz and 1 V. Y2O3 additions up to 1.0 mol% resulted in donor-doped behaviour in the Ba-excess BaTiO3, whilst higher additions resulted in acceptor-doped behaviour. The lattice parameter decreased with increasing Y content up to 1.0 mol%, whilst the parameters a and c increased at higher additions. The Curie temperature decreased with increasing Y content. The Y3+ ions preferentially occupied Ba sites, and at concentrations above 1.0 mol% Y, were incorporated into Ti sites. 20 refs.