Luminescence properties of Pr3+ and Ce3+ in KCaF3 single crystals

The optical excitation and luminescence spectra of (Pr3+,Ce3+) ions in KCaF3 are presented. High-resolution excitation and emission spectra of Pr3+ and Ce3+ were measured at temperatures between 77 and 293 K. First measurements of KCaF3 : Ce3+ crystal show that there are nonequivalent Ce3+ centers which radiate either in UV or visible range. The major Ce3+ nonequivalent center in KCaF3 is Ce3+ ion in the site with tetragonal site symmetry (S-4). Energy levels for the 4f(2) ground configuration of Pr3+ in KCaF3 were established from excitation and fluorescence spectra. Energy levels assignments were made assuming electric-dipole transition selection rules for S-4 site symmetry. Twenty-seven energy levels in the lowest six multiplets of the ground configuration were established. In the analysis of experimental data, the O-h magnetic-dipole selection rules were also considered to explain missing or weak transitions which are allowed in S-4. Spectra of Pr3+ in KCaF3 have been analyzed with a crystal-held Hamiltonians of S-4 or O-h symmetries including J mixing effects. Crystal-held parameters in these Hamiltonians have been determined by the minimization the RMS deviation between calculated and experimental energy Stark levels. We conclude that both model calculations in the S-4 and O-h site symmetries for Pr3+ in KCaF3, provide the basis for a consistently good correlation with data. (C) 1999 Published by Elsevier Science B.V. All rights reserved.