Optical spectroscopy study of neodymium in sodium alumino-borosilicate glasses

Over the composition range from peraluminous to peralkaline (RPA = Na2O/(Na2O + Al2O3) from 0 to 1), ultraviolet–visible spectroscopy was used to study the local environment of Nd–O in glasses (molar composition): 60SiO2 · 15B2O3 · xNa2O · (25 − x)Al2O3 · yNd2O3 (0 ⩽ x ⩽ 25 and y = solubility limit). Our study focused on Judd–Ofelt oscillator strength parameters: Ω2 – ligand field asymmetry and Ω6 – bond covalence. We explain the similarity between Ω2/Ω6 and the Nd2O3 solubility curve in terms of Nd partitioning into borate- and silicate-rich environments. However, Ω2/Ω6 is nearly independent of RPA for the glasses containing Nd2O3 at the solubility limit irrespective of glass composition, suggesting that average local Nd–O environment is nearly the same for all glasses.