Divalent cation conductivity of beta-alumina

Polycrystalline beta"-alumina has been ion exchanged with divalent cations such as Pb2+, Ca2+, and Mg2+ using molten salt eutectic mixtures. The results from EDAX and weight change measurements indicate that almost all the sodium ions in beta"-alumina were replaced by the divalent cations employed. The conductivities of the Pb2+ and Ca2+ specimens were tested using non-blocking electrodes. The Ca2+ beta"-alumina conductivity at 500°C was found to be 7.1 x 10^-4 (ohm cm)^-1 at an AC frequency of 200 khz. The AC conductivity of the Pb2+ beta "-alumina specimen was 1.6 x 10^-3 (ohm cm)^-1 at a temperature of 340°C and a frequency of 200 khz. Although the conductivities; measured in these divalent exchanged polycrystalline specimens were lower than those expected from single crystal specimens, the activation energies observed were very close to those measured in divalent ion exchanged single crystal specimens.