A luminescence spectroscopy and theoretical study of 4f–5d transitions ofCe3 + ionsin SrAlF5 crystals

Abstract

This research is focused on the 4f–5d transitions inCe3 + centers dopedinto tetragonal β-SrAlF5 single crystalsbelonging to the I41/a space group. The presence of four non-equivalentSr2 + sites in this compound leads to the appearance of three spectroscopically non-equivalentCe3 + luminescence centers, which can be well distinguished using a time-resolvedlaser spectroscopy technique. All 4f–5d transitions have slightly varyingexcitation and emission energies with characteristic probabilities resultingin several decay times that can be determined experimentally. One of thesecenters experiences strong perturbation due to a defect nearby, probably theO2 − impurity ionsubstituting for the F − ion and acting as a charge compensator as well. Identification of thesephotoluminescence centers is performed using crystal field calculations. The crystal fieldparameters are calculated for two identified centers using the structural data forSrAlF5; diagonalization of the crystal field Hamiltonian results in obtaining the splitting of theCe3 + 5d states. This method allows ‘regular’ unperturbedCe3 + centers withselected Sr2 + sites to be assigned.