Influence of silver ion concentration on dielectric characteristics of Li2O-Nb2O5-P2O5 glasses

Abstract

In this work we have studied the dielectric properties of Li2O-Nb2O5-P2O5: Ag2O glasses as a function of Ag2O concentration. Auxiliary studies viz., optical absorption, photoluminescence (PL), XPS and IR spectra have also been performed on these glasses. IR spectral studies have indicated that the host glass network doped with 1.0 mol% of Ag2O is highly polymerized. Optical absorption and PL studies have clearly exhibited absorption and emission bands due to surface plasmon resonance (SPR). From these studies, the presence of Ag0 -Ag+ clusters is established in the glass network and the concentration of such clusters is found to be the highest in the glass doped with 1.0 mol% of Ag2O. Finally, we have performed extensive studies on dielectric properties viz., dielectric constant, loss, electric moduli, impedance spectra and a.c. conductivity over broad ranges of frequency (0.01 Hz–1 MHz) and temperature (303–513 K). The glasses doped with higher content of Ag2O exhibited higher values of dielectric constant especially at lower frequencies and higher temperatures. The larger contribution from space charge polarization is predicted to be responsible for such higher values. In the glasses doped with low contents of Ag2O (<1.0 mol%) the polaron conductivity (due to the polaronic transfer between Ag0 and Ag+ ions) seemed to be dominant, whereas in the glasses containing more than 1.0 mol% of Ag2O, the ionic conduction (due to the diffusion of Ag+ and Li+ ions) appear to prevail. The impedance diagrams drawn between Z′ and Z″ have further supported the above-mentioned conclusions. From the overall analysis of the results of dielectric properties (including a.c. conductivity) with the aid of experimental results on spectroscopic studies, it is concluded that the glass containing more than 1.0 mol% of Ag2O exhibited predominantly ionic conductivity and hence such glasses may be useful as electrolytes for ionic conducting batteries.