Structure, thermal decomposition, vibrational and impedance spectroscopy studies of an rubidium cesium phosphate tellurate Rb1.84Cs0.16 HPO4Te(OH)6

The new crystals of phosphate tellurate family have been grown by slow evaporation at room temperature. The rubidium cesium phosphate tellurate Rb1.84Cs0.16HPO4Te(OH)6 (RbCsPTe) salt is monoclinic with the following unit cell dimensions: a = 8.295(4) Å, b = 7.067(4) Å, c = 12.289(6) Å, β = 90.330(9). The space group is P21/c with Z = 4. The structure was solved by Patterson methods and refined to a final R value of 0.056 for 1822 observed reflections. The RbCsPTe structure contains planes of statistically distributed (PO43-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{PO}}_{4}^{3 - }$$\end{document}) tetrahedra alternating with planes of (TeO66-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{TeO}}_{6}^{6 - }$$\end{document}) octahedra, Rb+/Cs+ cations are situated between these planes. The crystalline network is stabilized by mean of hydrogen bonds connecting cations and anions forming a three-dimensional network. Differential scanning calorimetry revealed three-phase transitions at 152, 187 and 207 °C. The thermal analyses (DTA) and (TG) of the title compound have proven that the decomposition of this material starts at a temperature equal to 227 °C. Raman and IR spectra in the frequency range 50–1300 and 500–4000 cm−1, respectively, exhibit the presence and independence of anionic groups in the structure and the importance of the strong hydrogen bonds. The Raman spectroscopy study at various temperatures evinces the presence of the phase transitions revealed in DSC and DTA. The rubidium cesium phosphate tellurate (RbCsPTe) was characterized by impedance spectroscopy technique. Complex impedance measurements are performed on this material as a function of both temperature and frequency. The activation energies obtained from the impedance and modulus spectra are similar, suggesting that the ionic transport in the investigated material can be described by a hopping mechanism.