Effects of co-doped Li+ ions on luminescence of CaWO4:Sm3+ nanoparticles

CaWO 4 , CaWO 4 :Sm 3+ and CaWO 4 :(Sm 3+ , Li + ) nanoparticles were synthesized by the precipitation method with addition of PEG 200. The X-ray diffraction patterns show that the obtained samples have a pure tetragonal phase. The CaWO 4 sample shows an emission peak at 418 nm originating from the charge-transfer transitions within the WO 4 2− complex. CaWO 4 :Sm 3+ and CaWO 4 :(Sm 3+ , Li + ) samples show emission peaks originating from the f–f forbidden transitions of the 4f electrons of Sm 3+ ions. The charge compensator of Li + can enhance the emission intensity effectively. It is found that the emission intensity of CaWO 4 :(3 mol% Sm 3+ , 4 mol% Li + ) phosphor is about double that of CaWO 4 :3 mol% Sm 3+ phosphor.