Concentration Dependence of Thermal Conductivity in Superionic Conductors

Abstract

By making use of the lattice gas model with a hopping term and Kubo’s formula, we have studied the mobile ion concentration dependence of the thermal conductivity in order to consider the effects of ion-ion correlation in superionic conductors. Theoretically, it is intriguing to investigate the concentration dependence of the thermal conductivity including the formulation in the framework of the lattice gas model. The thermal conductivity has symmetry with respect to ρ =0 .5, and at ρ =0a ndρ = 1 it is zero, as expected physically. The thermal conductivity first increases with the increasing concentration and has a maximum value at ρ =0 .5. It is understood that the thermal conductivity first increases with the concentration due to the increase of the repulsive interaction among the mobile ions and then takes a maximum value. Then, beyond this maximum, the thermal conductivity decreases with the concentration due to the decreasing vacancy of the ions. At ρ =0 .5, mobile ions and vacancies occupy the lattice sites alternatively.