Influence of BaO on spectral studies of Cr2O3 doped titanium-boro-tellurite glasses

Barium-titanium-boro-tellurite glasses containing the transition metal (TM) Cr3+ ions with different BaO mol% were prepared using the melt quenching method. From the XRD, SEM and EDS studies, it was confirmed that the prepared glasses were impurity-free and their atomic arrangement is non-crystalline in nature. The UV-visible spectra exhibited a dominant high absorption band corresponding to the enrgy of similar to 15974 cm(-1) and three weak low-intensity bands around 23641 cm(-1), 14881 cm(-1) and 14306 cm(-1). The identified bands are assigned to (4)A(2g)-> T-4(2g) (F), (4)A(2g)-> T-4(1g) (F), (4)A(2g)-> T-2(1g) (G) and (4)A(2g)-> E-2(g) (G) transitions respectively. The optical band gap values are increasing while the refractive index values are decreasing with increasing BaO content. The crystal-field parameter Dq values and Racah parameter (B) values were found to change non-linearly with the barium oxide content which suggests a change in the environment around Cr3+ ions. From the value of Dq/B, it can be concluded that the Cr3+ ions are localized in the weak crystal field sites. The EPR spectra which were recorded at X-band frequencies exhibited four resonance signals at g(1) approximate to 1.97, g(2) approximate to 2.38, g(3) approximate to 4.25 and g(4) approximate to 5.23. The theoretical g-values were evaluated from the Macfarlane's perturbation formulae. The FTIR and Raman spectra show broad peaks which are the characteristic features of the prepared glass component vibrating modes.