It was recalled that the substitution of the larger I anion for Br in this solid electrolyte had been shown to enhance ionic conductivity in the superionic phase and to reduce the superionic-covalent transition temperature. It was found here that it was possible to substitute appreciable quantities of the smaller Cl anion for Br. As the x-value was increased in Ag3S(Br1-xClx) samples, greater concentrations of Ag halide were removed from the sulfide halide lattice. However, X-ray diffraction measurements confirmed that the sulfide halide lattice persisted up to x = 0.50. In contrast to the case of I-substitution, the effect of replacing Br with Cl was to increase the transition temperature which separated the superionic and covalent phases of the sulfide halide component. The overall magnitude of the ionic conductivity did not change appreciably as a function of composition near to the superionic/covalent phase-transition temperature. However, the presence of increasing quantities of low-conductivity halide in these samples suggested that the ionic conductivity of the sulfide halide component was enhanced by Cl-substitution. The use of X-ray diffraction and specific heat measurements confirmed the presence of free Ag2S with increasing x-value. This led to an electronic conductivity contribution above room temperature.

R.B.Beeken, T.J.Wright, T.Sakuma: Journal of Applied Physics, 1999, 85[11], 7635-8