EPR, optical and physical studies on Cr3+ doped MgO-BaO-B2O3-TeO2 glasses

Physical, optical and Electron Paramagnetic Resonance (EPR) studies on 15MgO-15BaO-(59.8−x) B2O3-(10 + x) TeO2-0.2Cr2O3 (x = 0,10,20,30 mol%) glass samples are reported. EPR spectra exhibited two resonance signals at g = 4.8 and g = 1.98. The resonance signal with large zero field splitting parameter (D) and E/D ≤ 1/3 at g = 4.8 is attributed to isolated Cr3+ centers in strongly distorted octahedral sites, whereas the resonance signal at g = 1.98 is assigned to Cr3+ centers at axially distorted octahedral sites. The resonance signal at g = 4.26 is assigned to Fe3+ ions, which are present in the glass matrix as unwanted impurities. The resonance signal at g = 1.91 indicates the Cr3+-Cr3+ exchange coupled pairs. The two observed broad optical bands in the optical absorption spectra 16,025 cm−1 and 23,474 cm−1 are assigned to 4A2g(F)→ 4T2g(F) and 4A2g(F)→ 4T1g(F) transitions, respectively. The site symmetry of Cr3+ is C4v or C3v. Racah parameters, crystal field (Dq) parameters and energy gap are evaluated from the optical spectra. Various other physical parameters like density etc. have also been reported.