Spectroscopic investigations of manganese ions in microwave-prepared NaPO₃---PbO glasses

Abstract

The EPR spectra of microwave-prepared 70NaPO₃:30PbO glasses containing different weight percentages of manganese ions have been studied. The EPR spectra exhibit a well-resolved hyperfine pattern at g_eff ≈ 2.0. Optical absorption, fluorescent emission and excitation spectra of the glasses have been examined. The absorption spectrum exhibits a peak near 500 nm and this has been attributed to the spin-allowed ⁵E_g → ⁵T_2g transition of Mn²⁺ ions. The emission spectrum shows a band at 595 nm which has been assigned to the ⁴T_1g(G) → ⁶A_1g(S) spin-forbidden transition of Mn²⁺ ions in octahedral coordination. Concentration quenching of fluorescence was found to occur above 0.75 wt% of Mn²⁺ ions. The excitation spectra exhibit four bands characteristic of Mn²⁺ ions in octahedral coordination. From the observed band positions of the excitation spectra, the crystal field parameter D_q and the Racah interelectronic repulsion parameters, B and C have been calculated. A structural model is proposed based on the IR, Raman and MASNMR studies according to which Mn²⁺ ions are likely to occupy sites similar to Na⁺ ions in these glasses.