The electrical conductivity and thermoelectric power of Mn-doped BaTiO3 (1 mole%) and “undoped” BaTiO3 have been measured as functions of oxygen partial pressure (in the range of 10-16 to 1 atm) and temperatures (in the range of 900 to 1200°C), and compared with each other to differentiate the effect of the Mn-addition. It is found that the isothermal conductivity of Mn-doped BaTiO3 varies with increasing Po2 as σ ∝ \documentclass[12pt]{minimal}
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$$Po_2^{ - 1/4} $$
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$${\text{Po}}_2^{ - 1/6} $$
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$${\text{Po}}_2^{ + 1/6} $$
\end{document} , unlike previously reported. This behavior is well explained by the shift of the ionization equilibrium, \documentclass[12pt]{minimal}
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$${\text{Mn}}_{Ti}^x $$
\end{document}. The corresponding equilibrium constant, KA, is determined from the Po2 values demarcating those three different Po2 regions as \documentclass[12pt]{minimal}
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$$K_A /{\text{cm}}^{ - 3} $$
\end{document} =3.19×1022 exp(−1.69 eV/kT). Basic parameters involving carrier density and mobility, and defect structure of Mn-doped BaTiO3 are discussed in comparison with those of undoped BaTiO3.
