Preparation and Luminescence Properties of K₅La(MoO₄)₄:Tm³⁺, Dy³⁺ Phosphors for W-LED with High Thermal Stability

A series of K₅La_1 - x (MoO₄)₄:xTm³⁺ and K₅La_0.95 - y (MoO₄)₄:0.05Tm³⁺,yDy³⁺ phosphors have been synthesized via high-temperature solid-state reaction at 600°C for 8 h, and then their luminescence property and thermal stability were investigated. It was found that the K₅La_1 - x (MoO₄)₄:xTm³⁺ phosphors exhibited two strong blue emission peaks at 452 and 458 nm under excitation at 356 nm with the strongest intensity in the case of x = 0.05, whereas the K₅La_0.95 - y (MoO₄)₄:0.05Tm³⁺,yDy³⁺ phosphors exhibited another two characteristic peaks of Dy³⁺ at 479 and 574 nm, and Tm³⁺ could transfer energy to Dy³⁺. Notably, even at 473 K, the emission intensity of K₅La_0.95(MoO₄)₄:0.05Tm³⁺ and K₅La_0.875(MoO₄)₄:0.05Tm³⁺,0.075Dy³⁺ phosphors at 452 nm still kept 62.33% and 75.03% of those at room temperature, respectively, indicating a high thermal stability. Moreover, the emission spectra and color coordinates of the co-doped phosphors can be regulated via changing the excitation wavelength. Specifically, the color coordinates of K₅La_0.875(MoO₄)₄:0.05Tm³⁺,0.075Dy³⁺ was (0.3223, 0.3346) under excitation at 350 nm, very close to the standard white light, implying a potential in white light LED.