Stoichiometric silver beta alumina studied at 25, 300 and 500 degrees C by powder neutron diffraction

Abstract

The structure of stoichiometric (s) silver beta alumina, Ag1-xAl11O17+x2/; x=0.0, prepared via hydrogen reduction of a non-stoichiometric (NS) material with x=0.45 has been determined at 25 degrees C, 300 degrees C and 500 degrees C by Rietveld analyses of powder neutron diffraction data. In contrast to the single Ag site observed previously at 4.2 K, the silver ion distribution becomes increasingly diffuse with increasing temperature. At 25 degrees C the mirror plane structure is similar to that seen at 4.2 K, but apparently with some anti-Beevers-Ross site occupancy, and still with an increased c-axis constant compared with the NS parent. At 500 degrees C no silver cation site is well defined, consistent with a two-dimensional quasi-liquid state suggested by earlier diffuse X-ray scattering experiments.