The effect of sulfide substitution in the mixed conductor Cu7PSe6

Cu7PSe6 is a mixed conductor exhibiting structural phase transitions above and below room temperature that are accompanied by step-like changes in electrical conductivity. The substitution of S2− for Se2− in Cu7PSe6 significantly enhances electrical conductivity at room temperature compared to that observed for the pure compound. In the case of Cu7P(Se0.80S0.20)6, a nearly temperature-independent electrical conductivity exceeds 1 S/cm with no evidence of any phase transitions throughout the temperature interval 200–400 K. However, the ionic contribution accounts for just 2% of the total electrical conductivity in this solid solution at room temperature.

► Sulfide anions may be substituted for selenide anions in the mixed conductor Cu7PSe6. ► Moderate sulfide substitution significantly enhances electrical conductivity in these solid solutions. ► With a 20% sulfide substitution, a nearly temperature-independent electrical conductivity exceeds 1 S/cm. ► Ionic contribution represents just 2% of total conductivity for samples containing 20% sulfide anions.