Two-point dc ionic conductivity measurements in the superionic phase of Cu 2−xSe

Abstract

dc ionic conductivity (σ i) of the mixed superionic conductor Cu 2− x Se, with 0.01 ≤ x ≤ 0.26, is measured in the temperature range from 160 to 250 °C. The new two-point measuring method is presented; the experimental set-up is simplified and very small samples can be treated, which strongly increases the speed of the measurements. The temperature dependence of σ i is found to be Arrhenius, with only weakly concentration-dependent activation energy A = 125 ± 5 meV. For compositions x ≳ 0.1, the concentration dependence of σ i is linear, σ i ∝ (1−1.3 x). As x is decreased from 0.1 to zero, σ i is nonlinearly enhanced, which confirms the importance of ionic correlations in the mechanism of superionic conduction.