Phase transitions and vibrational study of (Cs3.5Rb0.5)[(Se0.85S0.15)O3]2[Te(OH)6]3 material

The ionic-protonic conductor (Cs_3.5Rb_0.5)[(Se_0.85S_0.15)O₃]₂[Te(OH)₆]₃ crystallizes in the orthorhombic system. The space group is Pccn. Three endothermic peaks in thermal behavior were detected for this compound at T₁ = 400 K, T₂ = 435 K and T₃ = 480 K, by DSC experiment. These transitions analyzed by dielectric measurements using the impedance and modulus spectroscopy techniques. Raman spectra of the material recorded at various temperatures (300-600 K) in the frequency range 100-1100 cm^-1 and IR spectra achieved at room temperature between 400 and 4000 cm^-1, confirm the presence of all the phase transitions detected in the material and show that anionic groups coexist independently in the same crystal.