Parametric analysis of crystal-field effects in rare-earth-metal disilicates doped with trivalent europium

Abstract

The u.v. and dye-laser excited luminescence spectra of the Eu³⁺-doped rare-earth-metal disilicates C-M₂Si₂O₇(M = Y, Lu, Sc, or In) were recorded at 77 and 300 K. The ⁷F_0–5 energy-level schemes of the Eu³⁺ ion derived from the spectral analysis were simulated with the aid of phenomenological crystal-field theory. The C₂ symmetry simulation with nine real and five imaginary parameters of the experimental crystal-field splittings of the energy levels was excellent with root mean square deviations varying between 4 and 6 cm^–1. The best-fit parameter values behave in a smooth manner as a function of the host cation in the structurally isomorphic disilicate series. The indium disilicate has slightly different values, however. The strength of the crystal-field effect decreases slightly with increasing ionic radius of the rare-earth-metal host. A comparison of the experimental parameter sets with those obtained for Eu³⁺-doped rare-earth-metal oxysalts revealed fundamental differences.