Fluorescence spectroscopic studies of Mn2+ ions in SrO–Al2O3–B2O3–SiO2 glass system

The SrO–Al2O3–B2O3–SiO2 glasses doped with different concentrations of MnO were synthesized and their spectroscopic studies were carried out. The UV–vis absorption spectrum of these glasses exhibited a broad band centered at about 428 nm identified as being due as being to 6A1(S) → 4T2 (G) tetrahedral transition of Mn2+ ions. With the increase in the concentration of manganese oxide, a new band at about 525 nm corresponding to 6A1g(S) → 4T1g(G) octahedral transition of Mn2+ ions is developed. The photoluminescence spectra of these glasses excited at 420 nm exhibited two luminescence bands at about 540 (green emission) and 632 nm (red emission). As the concentration of MnO is increased up to 1.5 mol%, the red emission band is observed to grow at the expense of green band. The analysis of these results coupled with FT-IR and ESR spectral results has indicated that in the glass containing 1.5 mol% of MnO, the manganese ions predominantly occupy octahedral positions and are found to be responsible for rich red emission.

► Optical absorption, ESR and PL studies reveal that Mn2+ ions occupy both octahedral and tetrahedral positions.
► Octahedral occupancy of Mn2+ ions is predominant in the glass containing about 1.5 mol% of MnO.
► Intensive red emission is observed when the concentration of MnO is about 1.5 mol% in the glass matrix.