Electrochemical Investigations on silver sulphide

Abstract The deviations (δ) from the stoichiometric composition has been determined for β-Ag 2 S at 200–325°C with the help of solid-state coulometric titration. The measurements give the activity of silver in the compound as a function of the stoichiometry. The significance of the results for the quantitative interpretation of the disorder of electrons in the compound is discussed. Because of the high disorder of the silver ions, the change of the thermodynamic activity with composition is only given by a change of concentration of the quasi-free electrons, or of defect electrons. Analysis of the experimental data shows that the effective electron mass increases slightly with temperature. From the electrochemical measurements, the band gap in the sulfide can be calculated and is at least 0.4 eV.