ESR, IR and Optical Absorption Studies of Co2+ ions in ZnO-PbO-B2O3 glass System.

Glassy system of composition x Co2O3-(40-x) ZnO-10PbO-50B2O3,
(where x = 0, 0.1, 0.3, 0.5 and 1 mol %) were prepared by conventional
melt-quenching technique. The X-Ray Diffraction pattern of the glass
samples shows no sharp peaks, indicating the amorphous nature. FT-IR
spectra of the glasses show vibration modes corresponding to stretching
of BO3 trigonal, BO4 tetrahedral units and of B-O-B bending bonds. The
observed red shift of optical absorption edge (UV cutoff) show
monotonous decrease in indirect optical band gap energy (Eopt) by
increasing Co2O3 content in the glasses based on their absorption
spectra. Absorption spectra of ZLB: Co2+ have exhibited two tetrahedral
bands corresponding to (4T1g (F) →4T1g (P)) and (4T1g (F) →4A2g (F))
transitions and an octahedral band in (4T1g (F) →2T1g (D)) transition.
ESR spectra exhibit characteristic resonance signals of Co2+ ions and a
well resolved six line hyperfine structure.