Mn-doped BaTiO 3 : Electrical Transport Properties in Equilibrium State

Abstract

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 ∝ \(Po_2^{ - 1/4} \) to ∝ \({\text{Po}}_2^{ - 1/6} \) to ∝ \({\text{Po}}_2^{ + 1/6} \) , unlike previously reported. This behavior is well explained by the shift of the ionization equilibrium, \({\text{Mn}}_{Ti}^x \). The corresponding equilibrium constant, KA, is determined from the Po2 values demarcating those three different Po2 regions as \(K_A /{\text{cm}}^{ - 3} \) =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.