The mechanism of enhanced luminescence in ion-codoped Lu2SiO5:Ce3+ phosphors

(Lu0.995−xMxCe0.005)2SiO5 (M=Li, Mg and Sc, x=0.00-0.01) phosphors were synthesized via a sol-gel technique, the luminescence enhancement effect by Li+, Mg2+, or Sc3+ codoping is comprehensively investigated by XRD, Raman, thermoluminescence and X-ray absorption near edge structure (XANES) spectra. The underlying reason of enhanced luminescence by ion codoping is revealed, and a mechanism of the luminescence enhancement effect based on the valence state variation of cerium is proposed. It can be safely concluded that the enhanced luminescence of Lu2SiO5:Ce3+ by ion codoping essentially originates from the increase in the population of Ce3+, which is directly proved by XANES. The difference in luminescence enhancement effect for different codopants can be reasonably explained by the electronegativity of the codopant.