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

摘要

Physical, optical and electron paramagnetic resonance (EPR) studies of 15MgO-15BaO-(59.8 – x)B2O3-(10.0 + x)TeO2-0.2Cr2O3 (x = 0, 10, 20, 30 mole %) glass samples have been reported. EPR spectra exhibited some resonance signals. The first one (g = 4.80) had a large zero field splitting parameter (D) and E/D ≤ 1/3, it was attributed to isolated Cr3+ centers in strongly distorted octahedral sites; the second one (g = 1.98) was assigned to Cr3+ centers at axially distorted octahedral sites. The resonance signal at g = 4.26 was assigned to Fe3+ ions, which were in the glass matrix as unwanted impurities. The resonance signal at g = 1.91 indicated the Cr3+-Cr3+ exchange coupled pairs. In the optical absorption spectra, the two observed broad optical bands with 16025 cm–1 and 23474 cm–1 were 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 were evaluated from the optical spectra. Various other physical parameters like density, etc., are also reported.