White light-emitting Ba0.05Sr0.95WO4:Tm3+ Dy3+ phosphors

Tm³⁺ and Dy³⁺ co-doped Ba_0.05Sr_0.95WO₄ phosphors were synthesized by a low temperature combustion method. The structures of the samples were SrWO₄ phase and were identified by X-ray diffraction. The surface topographies of Ba_0.05Sr_0.91WO₄:0.01Tm³⁺ 0.03Dy³⁺ were tested by scanning electron microscopy. The particles are ellipsoid, and their average diameter is approximately 0.5 μm. The emission spectra of Ba_0.05Sr_0.95WO₄:Tm³⁺ show a peak at 454 nm which belongs to the ³H₆→¹D₂ transition of Tm³⁺, and the optimum doping concentration of Tm³⁺ ions was 0.01. The emission spectra of Ba_0.05Sr_0.95WO₄:Dy³⁺ consist of the ⁴F_9/2 → ⁶H_13/2 dominant transition located at 573 nm, the weaker ⁴F_9/2 → ⁶H_15/2 transition located at 478 and 485 nm, and the weakest ⁴F_9/2 → ⁶H_11/2 transition located at 660 nm, and the optimum doping concentration of Dy³⁺ ions was 0.05. A white light is achieved from Tm³⁺ and Dy³⁺ co-doped Ba_0.05Sr_0.95MoO₄ crystals excited at 352–366 nm. With the doping concentration of Tm³⁺ fixed at 0.01, the luminescence of Ba_0.05Sr_0.95MoO₄:Tm³⁺ Dy³⁺ is closest to standard white-light emissions when the concentration of Dy³⁺ is 0.03; the chromaticity coordinates are (0.321, 0.347), and the color temperature is 6000 K.