Electrical conductivity and dielectric properties of MgO doped lithium phosphate glasses

The electrical and dielectrical properties of Li2O-P2O5-Al2O3 doped with MgO glasses were measured using complex impedance spectroscopy. IR study reveals the influence of gradual increase in MgO content on the glass structure. The Nyquist diagrams were investigated in terms of equivalent circuits due to resistors and constant phase elements (CPE). Constant-phase elements (CPE) were used in equivalent electrical circuits for the fitting of experimental impedance data. Complex impedance analysis showed the behavior of a dielectric relaxation non-Debye type. The ac conductivity increases with temperature following the Arrhenius law, with single apparent activation energy for conduction process. The variation of conductivity and high temperature activation energy with composition revealed the possibility of ionic contribution to the conductivity and a transition from predominantly polaronic conductive regime to ionic conductive regime around 1.5 mol% of MgO in lithium phosphate glasses. The frequency dependence of the electric conductivity follows a simple power law behavior, according to relation σac(ω) = σ(0) + Aωs, where s < 1. It was evident that the electrical transport process in the system was due to the hopping mechanism. The frequency and temperature dependence of the electrical modulus as well as dielectric loss parameters have exhibited a relaxation character.