Fabrication of ZnWO4:Sm3+, Bi3+, Li+ with tunable white light-emitting properties for W-LEDs

The color-tunable phosphor ZnWO4:Sm3+, Bi3+, Li+ has been prepared via a solid–state reaction method. The white light was attributed to the color mixture of blue–green and orange–red emission, which originated from the charge transfer transition of W–O and the transition emission of Sm3+, respectively. The obtained phosphors exhibited a strong traditional band at 305 nm and a new band at about 351 nm which comes from the 1S0–3P1 transition of Bi3+. White light with tunable color emission for ZnWO4:Sm3+, Bi3+, Li+ phosphors were demonstrated by simply controlling the ratio of Sm3+/Li+. The calculated chromaticity coordinates were varying from blue to white region. When excited at about 351 nm, these phosphors have a strong orange–red light. These results indicate that the phosphor of ZnWO4:Sm3+, Bi3+, Li+ which can generate tunable blue–white–red light may be a promising element for cost-effective diodes with near ultraviolet white light emitting properties.