Spectroscopic properties of PbO−Sb2O3−SiO2: MnO glass system

Abstract

PbO–Sb2O3–SiO2 glasses containing different concentrations of manganese ions ranging from 0 to 1.0 mol% were prepared. A number of studies viz., optical absorption, IR and ESR spectra of these glasses have been carried out. The results have been analyzed in the light of different oxidation states of Mn ions. The optical absorption spectral studies point out that the manganese ions predominantly exist in Mn2+ state if MnO is present in lower concentrations; when MnO is present in higher concentrations, the bands due to tetrahedral positions of Mn2+ ions are obscured with the presence of a new band due to Mn3+ ions with a meta−center at 480 nm. The EPR spectra of the glasses are characterized by six−line hyperfine structure centered at g ∼ 2.01 and another signal at g ∼ 4.3; a considerable decrease in the effective value of g is observed with increase in the concentration of MnO in the glass matrix. With the increase in concentration of MnO, the intensity and resolution of the sixtet pattern is observed to decrease. In the IR spectra as the concentration of MnO is increased, the intensity of band due to Si−O−Si symmetric stretching vibrations and symmetric stretching vibrations of SbO3 structural groups is observed to decrease with a shift towards considerably higher frequencies, where as the intensity of the band due to Si–O–Si Asymmetric vibrations, Si−O−Si rocking motion and symmetric bending vibrations of SbO3 is increased with a shift towards considerably lower frequencies. Thus the analysis of IR spectra also supports the standpoint that as the concentration of MnO is increased in the glass matrix; there is an increasing degree of disorder in the glass network.