Ionic-protonic conduction analysis and dielectric relaxation behavior of the rubidium ammonium arsenate tellurate

Abstract

The rubidium ammonium arsenate tellurate Rb2.42(NH4)0.58H2AsO4HAsO4.Te(OH)6 compound was obtained by slow evaporation at room temperature. The differential scanning calorimetry (DSC) has shown three phase transitions at 453, 483, and 491 K, confirmed by the differential thermal analysis (D.T.A). As for the differential thermogravimetric analysis (TG) curve, it has revealed that no mass loss was detected before 475 K. So, the phase transition observed at 453 K does not correspond to the decomposition of this material. Rb2.42(NH4)0.58H2AsO4HAsO4.Te(OH)6 was characterized by impedance spectroscopy technique measured in the 1 KHz–9.91 MHz frequency range from 298 to 483 K. Besides, the cole-cole (z” versus z’) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE), and Warburg element (W). Furthermore, the conductivity evolution versus temperature has shown the presence of the ionic-protonic superconduction phase transition. The dielectric properties’ dependence on both temperature and frequencies of the compound has been reported. The ionic-protonic conductivity and conductivity relaxation calculated from the impedance and modulus spectra, respectively, were found to be thermally activated.