Novel Red Phosphor of Gd, Sm co-Activated AgGdSmEu☐WO Scheelites for LED Lighting.

Gd and Sm 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. AgGdSmEu☐WO ( = 0.50, 0.286, 0.20; = 0.01, 0.02, 0.03, 0.3) scheelite-type phases (AGSE) have been synthesized by a solid-state method. A powder X-ray diffraction study of AGSE ( = 0.286, 0.2; = 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 AGSE demonstrate the strongest absorption at 395 nm, which matches well with commercially available UV-emitting GaN-based LED chips. Gd and Sm co-activation leads to a notable decreasing intensity of the charge transfer band in comparison with Gd single-doped phases. The main absorption is the F → L transition of Eu at 395 nm and the H → F transition of Sm at 405 nm. The photoluminescence emission spectra of all the samples indicate intense red emission due to the D → F transition of Eu. The intensity of the D → F emission increases from ~2 times ( = 0.2, = 0.01 and = 0.286, = 0.02) to ~4 times ( = 0.5, = 0.01) in the Gd and Sm co-doped samples. The integral emission intensity of AgGdSmEuWO in the red visible spectral range (the D → F transition) is higher by ~20% than that of the commercially used red phosphor of GdOS:Eu. A thermal quenching study of the luminescence of the Eu emission reveals the influence of the structure of compounds and the Sm concentration on the temperature dependence and behavior of the synthesized crystals. AgGdSmEuWO and AgGdSmEuWO, with the incommensurately modulated (3 + 1)D monoclinic structure, are very attractive as near-UV converting phosphors applied as red-emitting phosphors for LEDs.