Stoichiometry and structure of the super ionic conductor silver beta-alumina

Beta-alumina is a crystalline nonstoichiometric compound highly permeable to sodium and silver ions. The mobile ions are statistically distributed among a manifold of nearly equivalent sites in widely separated planes perpendicular to the hexagonal axis and two-dimensional ionic conduction results from the interchange of ions between sites in these planes. Sodium and silver beta-alumina are isomorphous but at room temperature there is a different distribution of potential mobile cations among the conduction sites.