The de-clustering influence of aluminum ions on the emission features of Nd³⁺ ions in PbO-SiO₂ glasses

Nd³⁺ doped lead alumino silicate glasses with varying concentration of Al₂O₃ (from 5 to 10 mol%) have been synthesized. The IR and Raman spectral studies of these glasses have indicated that there is a gradual increase in the depolymerization of the glass network with increase in the concentration of Al₂O₃. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were recorded at room temperature. From these studies, the radiative parameters viz., spontaneous emission probability A, the total emission probability, the radiative lifetime τ, the fluorescent branching ratio β of different transitions originated from ⁴F_3/2 level of Nd³⁺ ions have been evaluated. A clear increase in the quantum efficiency and luminescence emission of the two prominent NIR bands of Nd³⁺ ions viz., ⁴F_3/2→⁴I_{11/2, 13/2}, is observed with increase in the concentration of Al₂O₃. The increase has been attributed to the possible admixing of wavefunctions of opposite parities and due to the declusterization of Nd³⁺ ions by Al³⁺ ions in the glass network.