Characterization and photoluminescent enhancement of Li+ corporation effect on CaWO4:Eu3+ phosphor

The red-emitting phosphor of Eu3+ ions doped CaWO4 and lithium ions co-doped (Ca, Eu) WO4 have been synthesized by the solid-state reaction technology. The introduction of Li+ ions reduced the preparing temperature and the phosphors exhibited a very strong red emission. It is proved by X-ray diffraction and XPS spectrum that the Li+ ion substituted the Ca2+ in the lattice without changing the crystalline. The photoluminescence spectrum showed that after Li+ doping, the dominant emission peak of 5D0–7F2 centered at 617 nm was remarkably improved by a factor of 2.9, and the concentration quenching behavior was weakened until it is observed at 15 mol%. This is assigned to the incorporation of Li+ into host twinning the V″CaV″Ca and making a Schottky pair for charge compensation. Li+ acting as charge compensator is responsible for the enhancement of luminescent properties. The CIE coordinates were also calculated according to the NTSC system standard to be (0.682, 0.317), thus it is efficient enough to be used as red phosphor for NUV LED chips.