Two-dimensional silver fast-ion conduction in (LaO)AgS

The silver fast-ion conductor (LaO)AgS was examined in temperature-dependent ac impedance and time-of-flight neutron diffraction experiments. Comparison of our conductivity data with those published earlier suggests that the presence of unreacted Ag2S resulting from different sample preparation methods is the possible reason for severe discrepancies in the conductivity data of other authors. Anisotropic temperature factors obtained by Rietveld analysis of our neutron diffraction data indicate enhanced silver ion mobility in the a–b plane of the tetragonal structure. The observed silver ion density shows that the preferred conduction path is via interstitial (12 12 12) sites, i.e. along 〈110〉. (LaO)AgS is a two-dimensional silver fast-ion conductor.