Spectral analysis of single-crystal LiKGdF5 : Er$^{3+}$,Tb$^{3+}$

RADIOCHSingle-crystal LiKGdF5: Er3+, Tb3+ was synthesized by using hydrothermal techniques. After measuring luminescence and excitation spectra, we observed the up-converted green (H-2(11/2) --> I-4(15/2), S-4(3/2) --> I-4(15/2)) and red (F-4(9/2) --> I-4(15/2)) emissions, as well as the weak blue emissions from Er3+ ions in the crystal. Analysis indicates that the blue up-conversion occurs via a sequential absorption of three photons. By assuming the ion is in a C-2V instead of the actual C-2 site, a crystal-field (cf) calculation has been performed on the reduced F-7(J) basis of the ground F-7 term of the Tb3+ ion. Excellent correlation was obtained between the experimental transition energies and the computed level Structures. The cf parameter obtained is very well transferable to the Er3+ energy levels in LiKGdF5