On the defect structure of calcium titanate with nonideal cationic ratio

The defect structure of polycrystalline calcium titanate with Ca/Ti = 0.998, 0.995, and 0.992 was investigated by measuring the equilibrium electrical conductivity as a function of oxygen partial pressure (P_O2 = 10⁰–10^?20 atm) at 950–1050°C. These data were similar to that obtained in the sample with ideal cationic ratio. The deviation from ideal Ca-to-Ti ratio is found to be accommodated by the formation of neutral vacancy pairs, (V″_CaV^··₀). The results indicate that the single-phase field of calcium titanate extends beyond 50.201 mole% TiO₂.