Li+ ion constriction in presence of Bi2O3 and ac conductivity in Li2O.P2O5.Bi2O3 glasses

Glasses having composition (25+x)Li2O.(65-x)P2O5.10Bi2O3 (0≤x≤25 mol%) were investigated using impedance spectroscopy in the frequency range from 20 Hz to 1 MHz and in the temperature range from 150 to 300 deg. C. The ac and dc conductivities, activation energy of dc conductivity and conductivity relaxation are extracted from the impedance spectra. The complex impedance data have been analyzed using the conductivity and electric modulus formalisms to study the relaxation dynamics of charge carriers in these glasses. The observed conductivity spectra follow the power law with exponent 'n'. The exponent 'n' decreases with increase in Li2O:P2O5 ratio and has been correlated with both the constriction of the Li+ ions and the dimensionality of the available conduction pathways. The conductivity increases with increase in Li2O:P2O5 ratio and is ionic in nature. Summerfield scaling model has been applied to obtain single 'super curve' for all the ac conductivity spectra at various temperatures in the present glasses. However, a deviation from 'super curve' for various isotherms of conductivity spectra was also observed in high frequency region and at low temperatures.