Effect of cation substitution on fast Ag+ ion conductivity in Ag2CdI4

The order-disorder phase transition and ionic conduction in the pure and doped Ag2CdI4 were investigated by X-ray diffraction and electrical conductivity techniques. The lower conductivity of Ag2CdI4 in presence of Li+ relative to pure Ag2CdI4 is attributed to lattice contraction effecting lower mobility of ions. The Tl+ doped Ag2CdI4 exhibits higher conductivity in the high temperature phase and is found to be maximum at 8 mol% of Tl+ concentration. This increase in conductivity is discussed in terms of additional free volume generated by the partial substitution of Ag+ by larger Tl+. (C) 1997 Elsevier Science Ltd. All ridghts reserved.