Journal of the American Ceramic Society, Vol.90, No.1, 125-131, 2007
AC conductivity and electrical modulus studies on lithium vanadophosphate glasses
The lithium vanadophosphate (LVP) glasses were synthesized through a conventional melt quench method for various modifier (m) to formers (f) ratios (m/f) [m%Li2O/f%{0.3V(2)O(5)+0.7P(2)O(5)}, where the m/f=0.43, 0.66, 1.0, 1.5, and 1.63]. Nature, structure, and glass transition T-g temperature for the prepared LVP samples were characterized by X-ray diffraction, FTIR, and DSC techniques, respectively. Impedance measurements were made for the various m/f ratios of LVP glasses at 423 K and above temperatures. The bulk conductivity (sigma) and the activation energy (E-a) for the LVP glass samples were calculated, respectively, from the analyzed impedance data of the various m/f ratios measured at different temperatures, using Boukamp equivalent circuit software. The best conducting [sigma=4.83 x 10(-8) S/cm at 423 K] m/f ratio of LVP was found to be 60%Li2O-40% [0.3V(2)O(5)+0.7P(2)O(5)] and its activation energy (E-a)=0.59 eV. AC conductivity was calculated from the impedance data and analyzed using Jonscher's power law for various m/f ratios of the LVP glasses at different temperatures. The power law exponent s, evaluated from AC conductivity of the LVP glasses, exhibited a non-linear behavior with temperatures. Kohlrausch-William-Watts stretched exponential function was used to fit the calculated modulus data and ion relaxation behavior was studied for the LVP glasses.