Variability of the Sr/Ti Ratio in SrTiO ₃

TiO 2 is observed as a second phase in SrTiO 3 having Sr/Ti ≤ 0.995 (≥0.5 mol% excess TiO 2 ). The effect of excess TiO 2 on the equilibrium electrical conductivity at 1000°C is consistent with a solubility of <0.1 mol% TiO 2 with the formation of unassociated oxygen vacancies. More Ti0 2 is retained in solid solution when samples are quenched from the sintering temperature rather than furnace‐cooled. The effect of excess SrO on the equilibrium electrical conductivity also indicates some solid solubility.