Study of the CulCu2S system. conductivity of the solid solution Cu1+xI1−xSx(x<0.5)

A structural study of the CuICu₂S system has shown that a large solid solution ranges from pure CuI to Cu₃SI with a regular decrease of tehcell parameter ($\text{a=6.045 to 5.901}\text{A}\text{?}$); for richer Cu₂S concentrations, two-phase systems appear with the formation of a new Cu₇S₃I compound, and another solid solution exists for higher Cu₃S fractions (0.85<x<1). The ionic conductivity of the solid solution Cu_1+xI_1?xS_x (x<0.5) has been measured as a function of temperature between 54 and 307°C. The conductivity increases from 10^?7 ω^?1 cm^?1 (CuI) to 10^?3 ω^?1 cm^?1 (Cu_1.4I_0.6 S_0.4) at 25°C and then decreases until 10^?4 ω^?1 cm^?1 (Cu₃SI). In this last domain, no further phase transition occurs below the melting point and the low temperature γ phase can be considered as a stabilization of the high-conducting α phase. The variations of the conductivity are directly connected to those of the activation energy that decreases to a minimum value of 2.5 kcal mole^?1 for Cu_1.4I_0.6S_0.4.