Sambasiva Rao, M.V., Rajyasree, Ch., Narendrudu, T., Suresh, S., Suneel Kumar, A., Veeraiah, N., and Krishna Rao, D.
Transparent glass ceramics, synthesized from melt quenching followed by heat treatment, of the composition 10Na 2 O–30PbO–10Bi 2 O 3 –(50 − x )SiO 2 : x Cr 2 O 3 (mol%), where 0 ⩽ x ⩽ 0.5, were characterized with XRD, DTA, SEM and EDS. Physical and spectroscopic studies, viz., optical absorption, electron paramagnetic resonance (EPR), FTIR and Raman were investigated. The characterization of the host glass ceramic has revealed that the formation of a major phase of sodium silicate along with two minor phases such as lead silicate and bismuth oxide. By integrating Cr 2 O 3 to the host glass additional crystal phases viz., NaCrO 2 , Na 2 Cr 2 O 7 and Pb(CrO 4 ) which are the complexes of Cr 3+ and Cr 6+ ions were also developed. As the concentration of nucleating agent is increased, a part of the Cr 6+ ions is found to reduce in to Cr 3+ ions. Spectroscopic studies have revealed that with an increase in the concentration of Cr 2 O 3 from 0.1 to 0.5 mol%, there is a gradual increase in the intensity of vibrational modes of various asymmetric structural units of silicate, bismuthate and chromate in the glass ceramic network at the expense of symmetrical structural units. The analysis of the results of these studies has indicated that in the samples containing higher concentration of Cr 2 O 3 , chromium ions exists predominantly in Cr 3+ state and occupy the octahedral positions in glass ceramic matrix and such glass ceramic samples are suitable for lasing action. [ABSTRACT FROM AUTHOR]