Temperature dependence of thermal transport properties in spinel Cu1-xAgxIr2S4

Abstract

We investigated the thermal transport properties of Cu1-xAgxIr2S4 (0 ≤ x ≤ 0.05). The thermal conductivity of CuIr2S4 exhibits a sudden change at the metal-insulator transition (MIT) temperature, where the phonon thermal conductivity κph decreases sharply from the insulating phase (IP) to the metallic phase (MP). The decrease in κph is attributed to a decrease in the phonon mean free path l from the IP to the MP, which is caused by anomalous phonon scattering in the MP. The decrease in l at the MIT temperature becomes less pronounced with increasing x, and the absolute values of l in the MP for x = 0.025 and 0.05 are higher than that for x = 0. This behavior suggests that the anomalous phonon scattering is suppressed by Ag substitution. Compared with previously reported results for the effect of Zn substitutions at Cu sites, the phonon relaxation time exhibits a distinct behavior for Ag and Zn substitution.