NMR study of effects of moisture and composition in Na β''-alumina

23Na T1 measurements were performed over the temperature region 200-800K on a single crystal sample of Mg++-stabilized Na β''-alumina and on a polycrystalline sample of Li+-stabilized Na β''-alumina having slightly different Na concentration. These samples give the same activation energy (0.37 eV) below 500K but different activation energies above, which may be related to a high-temperature breakdown of superlattice ordering. 23Na lineshape studies of particles with 10μ and 200μ grain diameter exposed to moisture indicate rapid water motion along grain boundaries as well as slower penetration of the conduction planes. Drying experiments with methanol indicate the presence of a high concentration of water a short distance below the surface. (Auth.)