Effect of temperature and activator concentration on relaxation of excited states of Eu3+ in K5Li2La1−xEuxF10 crystals Original Research Article

Single crystals of K5Li2La1−xEuxF10 (where x=0.01,0.03,0.1,0.25,0.50,1) have been obtained from anhydrous fluorides by solid state reaction and then by the Bridgman crystal growth process. Optical properties of crystals were investigated at various temperatures between 5 and 300 K. Energy level scheme for Eu3+ has been constructed based on absorption and emission spectra recorded at 5 K. Emission from 5D3, 5D2, 5D1 and 5D0 levels has been studied in detail. It has been found that emission originating from the 5D0 and 5D1 levels is efficient and long lived for all Eu3+ concentrations. Estimated selfquenching rate of the 5D1 luminescence is as small as about 103 s−1 in K5Li2EuF10. Temperature dependence of this selfquenching is found to be consistent with a cross-relaxation process in which a donor ion makes the 5D1–5D0 transition and an acceptor ion makes the 7F1–7F3 transition. The 5D2 luminescence is considerably strongly influenced by activator–activator interaction but it is still easily detectable. The 5D3 luminescence is completely quenched in K5Li2EuF10.