Enhanced green upconversion luminescence in Ho3+ and Yb3+ codoped Y2O3 ceramics with Gd3+ ions

A detailed investigation on the effect of Gd3+ ions on the upconversion (UC) luminescence of Y2O3:Ho3+/Yb3+ was performed. The green UC emission intensity was obviously enhanced along with an increase in the relative content of Gd3+ ions from 0 mol% to 70 mol%, with a corresponding decrease in the Y3+ content from 91.9 mol% to 21.9 mol%. X-ray diffraction and decay time investigations confirmed that tridoping with Gd3+ ions can influence the local crystal field of the Y2O3 host lattice. Theoretical calculations illustrated that the enhancement in the green UC emission resulted from the induction of the Gd3+ ions, which increased the lifetimes in the intermediate 2F5/2 (Yb) and 5I6 (Ho) states, reduced the highest phonon cutoff energy of Y2O3 and dissociated the Yb3+ and Ho3+ ion clusters in the bulk ceramics.