The structural behaviour before the ionic–protonic superconduction phase transition and thermal properties in the caesium sulphate arsenate tellurate compound

Abstract

Caesium sulphate tellurate arsenate (CsSAsTe) crystallizes at 373 K in the trigonal system \( {\text{R}}\bar{3}m \). The crystal structures are built from isolated (\( {\text{HAsO}}_{4}^{2 - } , {\text{SO}}_{4}^{2 - } \)) tetrahedra and (\( {\text{TeO}}_{6}^{6 - } \)) octahedra, and they form tunnels where Cs+ cations and some hydrogen atoms are placed. Ac impedance measurements revealed that, upon heating, the compound undergoes a transformation into a phase of high conductivity. The charge carrier transport mechanism is obtained by comparison of ΔE f with ΔE σ. The activation energies for the (CsSAsTe) compound calculated, respectively, from the modulus and impedance spectra are approximately close, suggesting that transport properties above and below the superprotonic phase transition is probably due to H+ protons hopping mechanism. Thermal analysis at high temperature, DSC, DTA, TG, Ms/z = 18 and Ms/z = 32 confirms that the decomposition of this material starts at about T = 520 K, and it is manifested by the release of water vapour and O2 gas.