Visible green upconversion luminescence of Er3+/Yb3+/Li+ co-doped CaWO4 particles

Abstract The upconversion (UC) luminescence of Li + /Er 3+ /Yb 3+ co-doped CaWO 4 phosphors is investigated in detail. Single crystallized CaWO 4 :Li + /Er 3+ /Yb 3+ phosphor can be obtained, co-doped up to 25.0/5.0/20.0 mol% (Li + /Er 3+ /Yb 3+ ) by solid-state reaction. Under 980 nm excitation, CaWO 4 :Li + /Er 3+ /Yb 3+ phosphor exhibited strong green UC emissions visible to the naked eye at 530 and 550 nm induced by the intra-4f transitions of Er 3+ ( 2 H 11/2 , 4 S 3/2 → 4 I 15/2 ). The optimum doping concentrations of Yb 3+ /Li + for the highest UC luminescence were verified to be 10/15 mol%, and a possible UC mechanism that depends on the pumping power is discussed in detail.