Photoluminescence Properties of Sr₃WO₆:RE³⁺ (RE = Eu or Sm) Phosphors

Sr_3−1.5x WO₆:xRE³⁺ (RE = Eu or Sm) phosphors were synthesized with different concentrations of rare earth ions via the solid-state reaction method. The effects of the concentrations of rare earth ions on the structural, morphological, excitation and photoluminescence properties of the strontium tungstate phosphors were investigated. The results showed that the doping concentration has a significant effect on the properties of the Sr_3−1.5x WO₆:xRE³⁺ (RE = Eu or Sm) phosphors. All of the synthesized phosphors exhibited triclinic Sr₃WO₆ structures, regardless of the types and concentrations of the activator ions. The crystallite sizes gradually increased with the activator ion concentrations. The emission spectra of Eu³⁺-doped Sr₃WO₆ phosphors under excitation at 394 nm included an intense red band at 616 nm and seven weak peaks centered at 467, 490, 512, 537, 595, 655, and 709 nm. The emission spectra of the Sm³⁺-doped Sr₃WO₆ phosphors consisted of a strong orange band at 610 nm and three weak bands at 570, 656, and 722 nm. A Sm³⁺ concentration dependent quenching effect was observed in the range of 5–20 mol%. Color tuning from orange with a CIE chromaticity coordinate of (0.491, 0.315) to red with a CIE chromaticity coordinate of (0.637, 0.350) was observed as the concentration of Eu³⁺ ions increased from 1 mol% to 20 mol%. The results suggest that the optimal doping concentrations for fabricating red- and orange-light emitting phosphors with high color purity are 20 mol% of Eu³⁺ and 5 mol% of Sm³⁺, respectively.