Ti‐Rich Nonstoichiometric BaTiO 3 : I, High‐Temperature Electrical Conductivity Measurements

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Equilibrium electrical conductivity of nonstoichiometric poly‐crystalline BaTiO 3 with varying Ba:Ti ratios was investigated at temperatures between 800° and 1200°C and P o 2 from 10 −22 to I atm. A transition from p ‐type to n ‐type conductivity was observed. Although the electrical conductivity of different specimens varied slightly, these differences did not appear to be a function of the Ba:Ti ratio in the region investigated. An intrinsic band‐gap energy of ∼3.1 eV was calculated from the temperature dependence of the minimum conductivity. The O 2 partial pressure dependence of the isothermal n ‐type conductivity cannot be described by simple defect models incorporating only singly or doubly ionized O vacancies. Likewise, simple defect models incorporating cation vacancies are not consistent with the observed pressure dependence of the p ‐type conductivity. More complex defect models which correspond to the observed behavior over the entire range of temperature and P o 2 will be discussed in a subsequent paper.