Relaxation processes in TiO2-V2O5-P2O5 glass-ceramics

Bulk samples of the ternary TiO2-V2O5-P2O5 system have been synthesized by the melt-quenching technique. Xray diffraction and scanning electron microscopy with energy-dispersive spectroscopy were applied for structure and composition identification, whereby the presence of NASICON and Rutile type structures were identified. Dielectric properties were measured using impedance spectroscopy, at frequencies from 10 mHz to 1 MHz, and temperatures between 40 degrees C and 190 degrees C. Different relaxation models were applied to fit the experimental data. The electrical conductivity and activation energy of the glass matrix and crystalline particles were calculated and correlated to the structure of the material. The impedance spectra were analyzed with the complex dielectric modulus and the Distribution Function of Relaxation Times method to corroborate and complement the results of equivalent circuit models. The grain conductivity was shown to reach 10-1 S/m at 190 degrees C for the NASICON sample.