Ionic conductivity of tetragonal PbSnF4 prepared by solid state reaction in HF atmosphere

Abstract Tetragonal PbSnF 4 prepared by a solid state reaction under streaming gaseous HF has been characterized by X-ray Rietveld analysis, differential scanning calorimetry, differential thermal analysis and ac conductivity measurement. The room-temperature tetragonal phase is composed of the cationic framework made up of layers perpendicular to the c-axis with a sequence of PbPbSnSn. The conductivity vs. temperature curves between 170 and 573 K showed a gradual slope change from a region of high activation energy ( E ⋍ 30 kjmol −1 ) to that of low activation energy ( E ⋍ 10 kjmol −1 ) around room temperature. Such a behavior accompanied no lattice symmetry change, corresponding to a so-called diffuse phase transition.