PbO–Nb2O5–P2O5 glasses containing different concentrations of MnO ranging from 0 to 2.5 mol% were prepared. A number of studies viz., differential thermal analysis, infrared, optical absorption, luminescence, Raman and ESR spectra, magnetic susceptibility and dielectric properties (constant ɛ′, loss tan δ, ac conductivity σac over a range of frequency and temperature) of these glasses have been carried out. The results have been analyzed in the light of different oxidation states of manganese ions. The analysis indicates that when the concentration of MnO is around 1.0 mol%, manganese ions mostly exist in Mn2+ state, occupy network forming positions with MnO4 structural units and increase the rigidity of the glass network. When MnO is present in higher concentrations, these ions seem to exist mostly in Mn3+ state and occupy modifying positions.
Dr. Madhu Mohan N., M. Reddy, R., Veeraiaha, N., and Jayasankar, C. K., “Spectroscopic and dielectric studies on MnO doped PbO–Nb2O5–P2O5 glass system”, Journal of Alloys and Compounds, vol. 458, no. 1, pp. 66-76, 2008.