Study of the crystal field effect in REOF:Eu 3+ (RELa, Gd and Y) using optical spectroscopy and X-ray powder diffraction

Abstract

The luminescence spectra of the Eu 3+-doped rare earth oxyfluorides REOF:Eu 3+ (RELa, Gd and Y) were measured at room and liquid nitrogen temperatures. The interpretation of the spectra and the simulation of the 7F J ( J = 0–5) Stark levels were carried out with the aid of phenomenological crystal field (CF) theory for the C 3v symmetry of the RE 3+ site. The best-fit set of the six non-zero CF parameters yielded the r.m.s. deviations 8, 11 and 10 cm −1 between the experimental and calculated energy levels for YOF, GdOF and LaOF respectively. The strength of the CF effect increases from the LaOF to the YOF host. The X-ray powder diffraction data for LaOF and GdOF were analysed by the Rietveld profile refinement method. From these results the CF parameters were calculated with a modified point charge model. The parameters of ranks four and six were reproduced quite close to the experimental values. The calculated | B 0 2| values were too large, evidently owing to short-range covalency effects.