Novel Red Phosphor of Gd3+, Sm3+ co-Activated Ag x Gd((2- x)/3)-0.3- ySm y Eu3+0.30☐(1-2 x-2 y)/3WO4 Scheelites for LED Lighting

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

doi:10.3390/ma16124350

Novel Red Phosphor of Gd³⁺, Sm³⁺ co-Activated Ag _x Gd_{((2- x)/3)-0.3- y}Sm _y Eu³⁺_0.30☐_{(1-2 x-2 y)/3}WO₄ Scheelites for LED Lighting

Materials (Basel). 2023 Jun 13;16(12):4350. doi: 10.3390/ma16124350.

Authors

Vladimir A Morozov¹, Bogdan I Lazoryak¹, Aleksandra A Savina^{2

3}, Elena G Khaikina³, Ivan I Leonidov⁴, Alexey V Ishchenko⁵, Dina V Deyneko^{1

6}

Affiliations

¹ Chemistry Department, Moscow State University, 119991 Moscow, Russia.
² Skolkovo Institute of Science and Technology, 121205 Moscow, Russia.
³ Baikal Institute of Nature Management, Siberian Branch, Russian Academy of Science, 670047 Ulan-Ude, Russia.
⁴ Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences, 620990 Ekaterinburg, Russia.
⁵ NANOTECH Center, Ural Federal University, 620002 Ekaterinburg, Russia.
⁶ Laboratory of Arctic Mineralogy and Material Sciences, Kola Science Centre, Russian Academy of Sciences, 184209 Apatity, Russia.

Abstract

Gd³⁺ and Sm³⁺ 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_xGd_{((2-x)/3)-0.3-y}Sm_yEu³⁺_0.3☐_(1-2x)/3WO₄ (x = 0.50, 0.286, 0.20; y = 0.01, 0.02, 0.03, 0.3) scheelite-type phases (A_xGS_yE) have been synthesized by a solid-state method. A powder X-ray diffraction study of A_xGS_yE (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_xGS_yE demonstrate the strongest absorption at 395 nm, which matches well with commercially available UV-emitting GaN-based LED chips. Gd³⁺ and Sm³⁺ co-activation leads to a notable decreasing intensity of the charge transfer band in comparison with Gd³⁺ single-doped phases. The main absorption is the ⁷F₀ → ⁵L₆ transition of Eu³⁺ at 395 nm and the ⁶H_5/2 → ⁴F_7/2 transition of Sm³⁺ at 405 nm. The photoluminescence emission spectra of all the samples indicate intense red emission due to the ⁵D₀ → ⁷F₂ transition of Eu³⁺. The intensity of the ⁵D₀ → ⁷F₂ 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 Gd³⁺ and Sm³⁺ co-doped samples. The integral emission intensity of Ag_0.20Gd_0.29Sm_0.01Eu_0.30WO₄ in the red visible spectral range (the ⁵D₀ → ⁷F₂ transition) is higher by ~20% than that of the commercially used red phosphor of Gd₂O₂S:Eu³⁺. A thermal quenching study of the luminescence of the Eu³⁺ emission reveals the influence of the structure of compounds and the Sm³⁺ concentration on the temperature dependence and behavior of the synthesized crystals. Ag_0.286Gd_0.252Sm_0.02Eu_0.30WO₄ and Ag_0.20Gd_0.29Sm_0.01Eu_0.30WO₄, with the incommensurately modulated (3 + 1)D monoclinic structure, are very attractive as near-UV converting phosphors applied as red-emitting phosphors for LEDs.

Keywords: europium; gadolinium; incommensurately modulated structures; luminescence; phosphors; samarium; scheelite; silver; tungstates; white light-emitting diodes.

Abstract

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