Dielectric dispersion in PbO-PbF2-B2O3 glass system doped with Cr2O3

PbO-PbF2-B2O3 glasses containing different concentrations of chromium ions (introduced as Cr2O3) ranging from 0 to 0.4 mol % were prepared. The dielectric properties i.e., constant e{cent}, loss tand, ac conductivity sac over a range of frequency and temperature of Pb glasses have been carried out. The results have been analyzed in the light of different oxidation states of chromium ions with aid of the data on differential scanning calorimetry, infrared, optical absorption and ESR spectra. The analysis indicates that when the concentration of chromium ions is up to ~ 0.3 mol %, these ions mostly exist in Cr3+ state, occupy network-modifying positions with CrO6 structural units and at about 0.4 mol % a part of chromium ions seems to exist in Cr6+ state, adopting network forming positions with CrO42-structural units and causing an increase in the insulating strength of the glass.