Electric conductivity and relaxation in fluoride, fluorophosphate and phosphate glasses: analysis by impedance spectroscopy

Electrical properties of new set of glasses with formulation Pb0.3Ga0.2In0.15Zn0.15Ca0.2F2.35(1−x)(PO3)2.35x with x equal to 0, 0.1, 0.25, 0.75, 0.90 and 1.0 were investigated. Electrical measurements were carried out by impedance spectroscopy in the frequency range from 5 Hz to 13 MHz. All measurements were performed from 100 up to 30 °C below of the glass transition temperature (Tg) of each composition. The ac conductivity increases with temperature increasing following the Arrhenius law, with a single apparent activation energy for conduction process. The lowest activation energy value of 0.77 eV was derived for fluoride glass (x=0). Ea value reaches to 1.21 eV for fluorophosphate glass (x=0.75). The frequency dependence of the electric conductivity follows a simple power law behavior, in according to relation σ(ω)=σ(0)+Bωs. For all formulations, the exponent s is smaller than 1. The evolution of the various electrical parameters as a function of glass composition and temperature are discussed.