Thermal conductivity of Cu2Se taking into account the influence of mobile copper ions

Abstract

The temperature dependence of the thermal conductivity of nanostructured samples of copper selenide prepared by mechanochemical synthesis from initial pure components in a planetary ball mill followed by spark plasma sintering has been studied. The thermal conductivity of nanostructured samples was measured in the temperature range 410–860 K. At 410–780 K, the thermal lattice conductivity κ_ph varies insignificantly in the range 0.35–0.37 W/(m K). At a higher temperature T > 780 K, κph decreases to 0.19 W/(m K). To analyze the influence of mobile copper ions on the thermal conductivity of the lattice, molecular-dynamic calculations were performed using a classical interatomic potential obtained from ab initio calculations for the cubic β-Cu2Se modification. The simulation results demonstrate a high mobility of copper ions, and the calculated temperature dependence of the lattice thermal conductivity agrees with the experiment to 780 K. At a temperature T > 780 K, κ_ph deviates from the calculation results, and this deviation is most pronounced in the nanostructured material. As a result, at the maximum measurement temperature, the lattice thermal conductivity decreased to ~0.19 W/(m K), which agrees with available data for nanostructured Cu₂Se samples produced by various methods.