Molybdenum substitution induced luminescence enhancement in Gd₂W_1-xMo_xO₆:Eu³⁺ phosphors for near ultraviolet based solid-state lighting

A series of the Eu³⁺-activated Gd₂W_1-xMo_xO₆ phosphors were synthesized by a high-temperature solid-state reaction method. The phase composition, ultraviolet-visible diffuse reflectance spectra, photoluminescence and decay properties of the phosphors were investigated. Through adjusting the Mo⁶⁺ ion concentration, the excitation band of the studied sample was gradually shifted to longer wavelength. Under 376 nm excitation, the strong red emission at 610 nm and weak yellow emission centered at 591 nm were detected, indicating that Eu³⁺ occupies non-inversion symmetry sites in the host lattices. With elevating the dopant concentration, the emission intensity of synthesized products was greatly enhanced and achieved its optimum value when x = 0.95 which was 2.33 times higher than that of the Gd₂WO₆:Eu³⁺ compounds. The quantum efficiency of resultant samples was as high as 76.1%. Moreover, the Judd-Oflet theory was used to study the local structure environment behaviors of the Eu³⁺ ions in the host lattices. Finally, a red LED device, which consisted of a near-ultraviolet chip and prepared Gd₂W_0.05Mo_0.95O₆:Eu³⁺ phosphors, was successfully fabricated. These results confirmed that the Eu³⁺-doped Gd₂W_1-xMo_xO₆ phosphors have potential value as the red component for WLEDs.