Cesium hydrosulfate phosphate crystals: conductivity and real structure at increasing temperature

Superprotonic crystals Cs3(HSO4)2(H2PO4) and Cs4(HSO4)3(H2PO4) have been investigated by conducting atomic force microscopy at increasing temperature. Local volt-ampere characteristics have been measured and an increase in conductivity at 413–453 K for Cs3(HSO4)2(H2PO4) and Cs4(HSO4)3(H2PO4) by two and three orders of magnitude, respectively, has been recorded. Differences in the conductive characteristics of crystals of different compositions in the vicinity of the phase transition are shown. Information on topographic and electrical features of crystalline phases before and after exposure to temperature and electric fields has been obtained. The influence of external factors on the stability of the surface microstructure is evaluated. Possible mechanisms of structural-phase transformations of isostructural compounds with different ratio of sulfate and phosphate groups are discussed.