Ionic conductivity and phase stabilization in Cu- and Tl-substituted CsAg2I3

Samples of general formula CsAg2−xMxI3, x=0–0.4 and M=Cu and Tl, have been prepared and studied by powder X-ray diffraction, DSC and electrical conductivity measurements. X-ray diffractograms and DSC curves showed the possibility of stabilizing the high-temperature α-phase at lower temperatures in Tl-substituted samples, while such results were not obtained in Cu-substituted samples. Ionic conductivity measurements showed two regions corresponding to the low- and high-temperature phases. The transition temperature between the two phases was found to remain unchanged with the addition of Cu+ and decreased gradually with increasing Tl+. The ionic conductivity decreased in Cu-substituted samples and enhanced with the incorporation of Tl+ ion in the lattice of CsAg2I3. Dielectric constant was found to show behaviour similar to that of the ionic conductivity, and this is an evidence of the predominant effect of ion hopping on this property.