Influence of structure on the optical spectra of Eu3+ in Pb(PO3)2 glass: molecular dynamics simulation and crystal-field theory

Abstract

An investigation of the structural factors which lead to the marked differences between various spectral features of rare-earth-metal ions doped in metal metaphosphate and silicate glasses is reported. The investigation was based on a simulated structural/spectral model of an Eu³⁺-doped lead metaphosphate glass [Eu³⁺ : Pb(PO₃)₂] that was compared to a previously reported Eu³⁺-doped sodium disilicate glass [Eu³⁺ : Na₂Si₂O₅]. The models were generated with a computational method that couples molecular dynamics simulation and point-charge crystal-field calculations. It is proposed that the marked differences in several spectroscopic features of Eu³⁺ ions doped in a lead metaphosphate glass are essentially due to a reduction in the width of the energetic distribution of local fields experienced by the Eu³⁺ ions. This distribution is shown to be influenced considerably by the presence of medium-range order in the local environment of the Eu³⁺ ions due to the lack of rigidity of the phosphate backbone.