Mg<inf>2</inf>KH(XO<inf>4</inf>)<inf>2</inf>·15H<inf>2</inf>O (X = P, As) containing acidic dimer units: Electrochemical impedance spectroscopy, IR spectroscopy and DSC studies

Abstract

The electrical properties of little known compounds of the type Mg2KH(XO4)2·15H2O (X = P, As), their dc and ac conductivity and complex impedances are studied for the first time by Electrochemical Impedance Spectroscopy in narrow temperature interval from room temperature until 76 °C. These compounds present interesting electrical behavior with change of the conductivity mechanism and sharp increase in conductivity to ∼10−2S m−1 when subjected to thermal treatment without structural changes. The complex impedance plots confirm the contribution of two relaxation mechanisms, through grains and grain boundaries, the later becoming dominant at higher temperatures. The ac conductivity obeys Jonscher's power law and is in good agreement with the correlated barrier hopping model. In order to explain their conductivity behavior, the salts are additionally studied by differential scanning calorimetry (DSC), infrared and attenuated total reflectance spectroscopy at higher temperatures.