Journal Article

Novel Red Phosphor of Gdsup.3+, Smsup.3+ co-Activated AgIx/IGdsub./3WOsub.4 Scheelites for LED Lighting

Morozov, Vladimir A, Khaikina, Elena G, Deyneko, Dina V, Lazoryak, Bogdan I, Leonidov, Ivan I, Savina, Aleksandra A, Ishchenko, Alexey V

2023

Overview

Gd[sup.3+] and Sm[sup.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. AgxGd[sub.((2−x)/3)−0.3−y]SmyEu[sup.3+] [sub.0.3]☐[sub.(1−2x)/3]WO[sub.4] (x = 0.50, 0.286, 0.20; y = 0.01, 0.02, 0.03, 0.3) scheelite-type phases (AxGSyE) have been synthesized by a solid-state method. A powder X-ray diffraction study of AxGSyE (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 AxGSyE demonstrate the strongest absorption at 395 nm, which matches well with commercially available UV-emitting GaN-based LED chips. Gd[sup.3+] and Sm[sup.3+] co-activation leads to a notable decreasing intensity of the charge transfer band in comparison with Gd[sup.3+] single-doped phases. The main absorption is the [sup.7]F[sub.0] → [sup.5]L[sub.6] transition of Eu[sup.3+] at 395 nm and the [sup.6]H[sub.5/2] → [sup.4]F[sub.7/2] transition of Sm[sup.3+] at 405 nm. The photoluminescence emission spectra of all the samples indicate intense red emission due to the [sup.5]D[sub.0] → [sup.7]F[sub.2] transition of Eu[sup.3+]. The intensity of the [sup.5]D[sub.0] → [sup.7]F[sub.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[sup.3+] and Sm[sup.3+] co-doped samples. The integral emission intensity of Ag[sub.0.20]Gd[sub.0.29]Sm[sub.0.01]Eu[sub.0.30]WO[sub.4] in the red visible spectral range (the [sup.5]D[sub.0] → [sup.7]F[sub.2] transition) is higher by ~20% than that of the commercially used red phosphor of Gd[sub.2]O[sub.2]S:Eu[sup.3+]. A thermal quenching study of the luminescence of the Eu[sup.3+] emission reveals the influence of the structure of compounds and the Sm[sup.3+] concentration on the temperature dependence and behavior of the synthesized crystals. Ag[sub.0.286]Gd[sub.0.252]Sm[sub.0.02]Eu[sub.0.30]WO[sub.4] and Ag[sub.0.20]Gd[sub.0.29]Sm[sub.0.01]Eu[sub.0.30]WO[sub.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.

• Publisher: MDPI AG
• Subject: Light-emitting diodes