Raman and Dielectric Studies of Si₅P₆O₂₅: Conduction Mechanism and Relaxation Process

Si₅P₆O₂₅ was synthesized by reacting phosphoric acid and silica gel in a 1:1 molar ratio (P₂O₅/SiO₂). X-ray diffraction and Rietveld refinement analysis confirmed the formation of a single crystalline phase with a trigonal crystal structure belonging to the R-3 space group. Raman spectroscopy identified the presence of Si-O and P-O bonds within Si-O-Si, Si-O-P and P-O-P linkages. The dielectric properties and relaxation behavior of this material were investigated using complex impedance spectroscopy at a temperature range of 30–230 °C and a frequency range of 10 Hz to 1 MHz. The results indicated that the AC conductivity followed Jonscher’s power law, suggesting correlated barrier-hoping (CBH) as the appropriate conduction mechanism model. According to the Almond-West formalism, the frequency dispersing ionic conductivity is independent of temperature. Modulus analyses confirmed the existence of a non-Debye relaxation behavior. The decrease in dielectric constant with increasing frequency suggested a dispersion region arising from a relaxation polarization process within the material.