EPR AND OPTICAL ABSORPTION STUDIES OF Mn2+ IONS IN ALKALI BOROTELLURITE GLASSES

Abstract

Electron paramagnetic resonance (EPR) and optical absorption spectra of Mn2+ ions in alkali borotellurite glass systems have been studied. The EPR spectra of all the glass samples exhibit three resonance signals at g ≈ 2.0, g ≈ 3.3 and g ≈ 4.3. A six line hyperfine structure has also been observed at g ≈ 2.0. The concentration and temperature dependence of EPR signals were studied for Mn2+ ions in potassium borotellurite glass samples. The zero-field splitting parameter D has been calculated for different alkali borotellurite glass samples from the intensities of the allowed hyperfine lines. The paramagnetic susceptibility was calculated from the EPR data at various temperatures and the Curie constant was calculated from the 1/χ versus T graph. The optical absorption spectrum exhibits a single broad band near 498 nm and this has been attributed to the spin-allowed 5Eg → 5T2g transition of Mn3+ ions in octahedral symmetry. The optical band gap energy (E opt ) and Urbach energy (Δ E) were calculated from their ultraviolet edges. The optical band gap energy varies between 3.38 and 3.61 eV and increases from Li to K glasses.