Site-occupancy of yttrium as a dopant in BaO-excess BaTiO3

The site-occupancy of yttrium in BaO-excess barium titanate (BaTiO3) has been studied following pressureless-sintering of Y2O3-doped compositions with the fast-firing technique in a conventional furnace. Grain growth inhibition to an average grain size (Gav) of ≈3 μm occurs at 0.30 mol% Y2O3 when the ceramic is sintered at temperatures below 1350 °C. Sintering at 1450 °C, however, requires 0.50 mol% Y2O3 for grain growth inhibition to become effective. The concentration difference of 0.30–0.50 mol% for grain growth inhibition is attributed to the temperature dependence of the Y2O3-doping level at which the transition from predominantly electron to vacancy compensation takes place. Y3+ may act as a donor or an acceptor when substituting, respectively for the Ba2+- and Ti4+-site. This conclusion is supported by conductivity measurements for fast-cooled samples at room temperature and by the grain growth anomaly observed during sintering.