Synthesis,Structural Study and Phase Transitions Characterization by Thermal Analysis and Vibrational Spectroscopy of an Ammonium Rubidium Arsenate Tellurate

The Rb_2.42(NH₄)_0.58(HAsO₄)(H₂AsO4)·Te(OH)₆ crystals(denoted by RbNAsTe) crystallize in the monoclinic system, space group P2₁/n with the following parameters:a=1.3059(5) nm, b=0.6755(3) nm, c=1.6675(6) nm, β=94.126(4)°, Z=4 and V=1.46733(10) nm³. Thermal analyses(DSC, DTA and TG) confirm the presence of the phase transition and the temperature of the decomposition. The vibrational spectroscopy study at room temperature show the presence and the independence of anionic groups, cationic groups, and give more importance to the hydrogen bonds. Raman spectra were recorded in the temperature range of 298-503 K. The temperature dependence of the Raman line shift, intensity reduction and the half width detects the phase transitions and confirms their nature. So, the phase transition at 453 K corresponds to the superprotonic-ionic conduction phase transition, and those at 483 and 491 K correspond to the decomposition of our material.