Novel Red Phosphor of Gd 3+ , Sm 3+ co-Activated Ag x Gd ((2- x )/3)-0.3- y Sm y Eu 3+ 0.30 ☐ (1-2 x -2 y )/3 WO 4 Scheelites for LED Lighting.

Gd 3+ and Sm 3+ co-activation, the effect of cation substitutions and the creation of cation vacancies in the scheelite-type framework are investigated as factors influencing luminescence properties. Ag x Gd ((2- x )/3)-0.3- y Sm y Eu 3+ 0.3 ☐ (1-2 x )/3 WO 4 ( x = 0.50, 0.286, 0.20; y = 0.01, 0.02, 0.03, 0.3) scheelite-type phases (A x GS y E) have been synthesized by a solid-state method. A powder X-ray diffraction study of A x GS y E ( x = 0.286, 0.2; y = 0.01, 0.02, 0.03) shows that the crystal structures have an incommensurately modulated character similar to other cation-deficient scheelite-related phases. Luminescence properties have been evaluated under near-ultraviolet (n-UV) light. The photoluminescence excitation spectra of A x GS y E demonstrate the strongest absorption at 395 nm, which matches well with commercially available UV-emitting GaN-based LED chips. Gd 3+ and Sm 3+ co-activation leads to a notable decreasing intensity of the charge transfer band in comparison with Gd 3+ single-doped phases. The main absorption is the 7 F 0 → 5 L 6 transition of Eu 3+ at 395 nm and the 6 H 5/2 → 4 F 7/2 transition of Sm 3+ at 405 nm. The photoluminescence emission spectra of all the samples indicate intense red emission due to the 5 D 0 → 7 F 2 transition of Eu 3+ . The intensity of the 5 D 0 → 7 F 2 emission increases from ~2 times ( x = 0.2, y = 0.01 and x = 0.286, y = 0.02) to ~4 times ( x = 0.5, y = 0.01) in the Gd 3+ and Sm 3+ co-doped samples. The integral emission intensity of Ag 0.20 Gd 0.29 Sm 0.01 Eu 0.30 WO 4 in the red visible spectral range (the 5 D 0 → 7 F 2 transition) is higher by ~20% than that of the commercially used red phosphor of Gd 2 O 2 S:Eu 3+ . A thermal quenching study of the luminescence of the Eu 3+ emission reveals the influence of the structure of compounds and the Sm 3+ concentration on the temperature dependence and behavior of the synthesized crystals. Ag 0.286 Gd 0.252 Sm 0.02 Eu 0.30 WO 4 and Ag 0.20 Gd 0.29 Sm 0.01 Eu 0.30 WO 4 , with the incommensurately modulated (3 + 1)D monoclinic structure, are very attractive as near-UV converting phosphors applied as red-emitting phosphors for LEDs.