Compositions of the form, (1-x)Ag2SO4-xCaSO4, where x ranged from 0.01 to 0.20, were prepared by slow cooling of the melt or by quenching using a twin roller technique. The solid solubility limit of Ca2+ was determined by using X-ray powder diffraction and scanning electron microscopy. Conductivity studies, using an impedance technique, were carried out at low and high temperatures so as to include both of the structural modifications of Ag2SO4. In the high-temperature region (above 417C), the conductivity was found to be greatest for a 7% vacancy concentration of added CaSO4. However, in the low-temperature orthogonal phase, a decrease in conductivity within and above the solid solubility limit was observed. The concept of lattice distortion (contraction) due to the partial substitution of Ag+ by Ca2+ was introduced in order to explain a decrease in conductivity of the orthogonal phase. Interfacial reactions and surface defect chemistry were invoked in order to explain the decrease in conductivity which occurred when CaSO4 was dispersed in Ag2SO4.

K.Singh, S.M.Pande, S.S.Bhoga: Journal of Solid State Chemistry, 1995, 116[2], 232-9