Compensation effect for electrical conductivity and its applications to estimate oxygen diffusivity in minerals

Abstract

The compensation effect for electrical conductivity is observed for minerals such as calcite, corundum, enstatite, ferrosilite, olivine, leucite, and periclase, which is referred to a linear correlation between the natural logarithm of preexponential factor and activation energy for the electrical conductivity in each mineral. It is shown that the electrical conductivity due to different conducting species tends to converge to a constant at a characteristic temperature in each mineral. On this basis, the preexponential factor for the oxygen diffusion coefficient is calculated from the electrical conductivity by the Nernst-Einstein equation, while the activation energy for oxygen diffusion is determined by anion porosity. The estimated oxygen diffusion coefficients from the electrical conductivity in minerals obey the compensation law well, and the linear compensation equation is in good agreement with that from the experimentally determined oxygen diffusion data. Experimentally determined cation diffusion coefficients also test the validity of our method. Comparison between the estimated oxygen diffusion coefficients and the determinations by the ionic porosity method shows that the present method provides useful constraints on the other empirical model to predict diffusion coefficient.