Optical spectroscopy and thermal quenching of the Ce3+ luminescence in yttrium oxysulfate, Y2O2[SO4]

Photoluminescence and excitation spectrum of Ce3+ activated yttrium oxysulfate, Y2O2[SO4] has been investigated in the 10–300 K temperature region. The Stokes shift of the Ce3+ emission is small (0.3 eV). The crystal field splitting and the centroid shift of the Ce3+ 5d state have been derived from the low temperature excitation spectrum. At room temperature, the quantum efficiency of the Ce3+ emission is low. The thermal quenching of Ce3+ lifetime observed for T > 200 K is attributed to the photoionization of the Ce3+ 5d electron. In Y2O2[SO4], the Ce3+ ions are coordinated with four “free” oxygen ions, which do not occur in the coordination polyhedra of the [SO4]2− groups. We present evidence from this work and from the data presented in the archival literature that the Ce3+ luminescence efficiency is low at room or slightly above room temperature in materials, which offer “free” oxygen ions in the first coordination sphere of the Ce3+ ion.