Electronic spectra and optical band gap studies in neodymium chlorophosphate glasses

The present work aims to study the variation of optical band gaps, intensity parameters, and radiative lifetimes with different metal ions in various chlorophosphate glasses. Different chlorophosphate glasses in the composition range 50P2O5+30Na2HPO4+19.5RCl (R=Li, Na, K, Ca and Pb) with 0.5 mol% Nd2O3 were prepared by quenching melts consisting of the above chemicals (1100–1200°C, 1.5–2 h) between two brass plates. Using the optical absorption spectra, the optical properties have been systematically studied. The position of the absorption edge and hence, the values of optical band gaps have been reported. Except for potassium, the position of the fundamental absorption edge shifts to longer wavelengths with an increase of average molecular weight of the glass. Judd–Ofelt analysis is used along with a spectral analysis to calculate the intensity parameters, radiative lifetimes and branching ratios. The lifetime of all the states are high in these chlorophosphate glasses when compared with chloroborate glasses. There is no relation between the spontaneous emission probabilities and ion packing ratios in these phosphate glasses as observed in other glass systems. The predicted radiative transition probabilities (A), radiative lifetimes (τR), branching ratios (β) and integrated absorption cross-sections (Σ) for certain excited states of Nd3+ doped glasses have also been reported.