Alternating-current conductivity data for this binary system were interpreted in terms of a positive mixed-cation effect upon cation conductivity. This had features in common with the positive mixed alkali/cation effects which were observed for the Na2SO4-Rb2SO4 and Ag2SO4-Rb2SO4 systems. The data suggested that other factors, such as ion-ion interaction, bonding, or so-called lattice loosening could promote ionic conductivity in isomorphic sulfates; together with a larger isovalent guest ion-free volume contribution. The relatively constant activation energy for ionic conductivity (about 45kJ/mol) was suggested to reflect a quasi-equal inter-site electrostatic potential energy for the mobile cation in the hexagonal structure and to indicate that the defect formation enthalpy term was zero or negligible. The ion transport mechanism was supposed to be of percolation type, with structural connectivity being the critical parameter. Differential scanning calorimetry data revealed an interesting solid-phase transition behavior.

Y.Lu, E.A.Secco: Journal of Solid State Chemistry, 1995, 114[1], 271-6