AC ionic conductivity investigations on the CsK(SO4)·Te(OH)6 material

Single crystals of CsK(SO₄)·Te(OH)₆ are obtained by slow evaporation at room temperature. Differential scanning calorimetry (DSC) measurements have been carried out in the temperature range 350–650 K. It reveals three anomalies in the studied temperature range. Complex impedance measurements are performed on this material as a function of both temperature and frequency. The electric conduction and dielectric relaxation have been studied. The temperature dependence of DC conductivity indicates that the sample became an ionic conductor at high temperature. The frequency dependence of conductivity follows the Jonscher’s dynamic law. The high level of conductivity at high temperature is explained by the dynamical disordering of protons between the neighboring SO₄ groups. This behavior indicates the presence of superprotonic phase transition in CsK(SO₄)·Te(OH)₆.