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.