Mn-doped BaTiO3: Electrical Transport Properties in Equilibrium State

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} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$Po_2^{ - 1/4} $$ \end{document} to ∝ \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $${\text{Po}}_2^{ - 1/6} $$ \end{document} to ∝ \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $${\text{Po}}_2^{ + 1/6} $$ \end{document} , unlike previously reported. This behavior is well explained by the shift of the ionization equilibrium, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $${\text{Mn}}_{Ti}^x $$ \end{document}. The corresponding equilibrium constant, KA, is determined from the Po2 values demarcating those three different Po2 regions as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$K_A /{\text{cm}}^{ - 3} $$ \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.