Photoluminescence Characteristics of a New Thiogallate‐Based Green‐Emitting Phosphor: MgGa₂S₄:Eu²⁺

Abstract

A new thiogallate-based green-emitting phosphor, MgGa 2 S 4 : Eu 2+ , was first synthesized via a high-temperature solid-state reaction in a CS 2 atmosphere. We then investigated the structures and luminescent properties of the MgGa 2 S 4 :Eu 2+ phosphors. The MgGa 2 S 4 :Eu 2+ phosphors can be excited efficiently by UV-visible light in the wavelength range from 350 to 520 nm and they emit an intensely green light with emission bands peaking at 538 nm. The optimal concentration for Eu 2+ in MgGa 2 S 4 was found to be about 6 mol%, and the corresponding concentration quenching mechanism was the electric multipole-multipole interaction. The quenching temperature was calculated to be 402 K, and the Huang-Rhys factor was about 4. The energy barrier for thermal quenching was calculated to be 0.28 and 0.27 eV by the two types of the Arrhenius equations. The small variation in the color coordinates of MgGa 2 S 4 :Eu 2+ under high temperatures indicates that the assynthesized phosphor has good color stability. Due to their broadband absorption in the 350-520 nm wavelength range, these phosphors may be able to fulfill the requirements for application in the development of Ga(In)N-based white LEDs.

Thermal quenching of Eu 2+ emission in Ca- and Sr-Ga 2 S 4 in relation with VRBE schemes

“…27 When doped with Eu 2+ , they show broad excitation bands in ultraviolet and blue regions, and a narrow FWHM (  50-60 nm) emission in the green region (500-560 nm). 14,15,27 These properties make Eu 2+ -doped MGa 2 S 4 very attractive as conversion phosphors for blue-emitting LEDs and backlight applications.…”

“…The optical properties of Eu 2+ -doped ZnGa 2 S 4 and MgGa 2 S 4 are very close to each other. 14,15 Recently, Joos 29,30 In the case of Eu 2+ -doped BaGa 2 S 4 , the FWHM is 60 nm, 10 which may be related to the fact that Eu 2+ can occupy both Ba sites and/or to the larger Stokes shift, which is 0.5 eV for M=Ba versus 0.26 eV for M=Ca and Sr.…”

“…7 Eu 2+ -doped thiogallates, in particular CaGa 2 S 4 , SrGa 2 S 4 and BaGa 2 S 4 , , have shown interesting luminescence properties which makes them attractive for blue-excited LED devices. [8][9][10][11][12][13][14][15] However, from an application point of view, the thermal quenching of Eu 2+ emission in these compounds at the operation temperature of the LED chip, which can reach 150ºC (420 K), is a major problem. Literature reports that T 50% , defined as the temperature at which luminescence intensity drops to 50% of the initial lower temperature value, is at 400 K for Eu 2+ -doped CaGa 2 S 4 , 16 and at 475 K for Eu 2+ -doped SrGa 2 S 4 when compared with the initial intensity at room temperature.…”

Synthesis and Luminescence Properties of Blue‐Emitting Phosphor Eu2+‐Doped Zinc Fluoro‐Phosphate Zn2[PO4]F

“…Lifetimes of Eu 2+ ions emission are usually in the range of 0.2–2 μs . The luminescent properties of Eu 2+ ‐doped solids have been widely studied during the past decades duo to its significant applications such as lamps lighting, white light‐emitting diodes (W‐LEDs), plasma display panels, long‐lasting fluorescence, X‐ray screen, and medical devices, etc …”

Broadband Luminescence in Rare Earth Doped Sr2SiS4: Relating Energy Levels of Ce3+ and Eu2+

“…Recently, protective coatings of luminescent particles were successfully applied to enhance the stability of these sulfide materials [3,4,5]. Particularly vivid are the studies on binary sulfides [6,7,8,9,10,11], thiogallates [12,13,14,15] and thiosilicates [16,17,18,19,20,21,22,23,24,25]. The thiosilicates are, in many practical aspects, comparable to the thiogallates, but considering the depletion of certain natural resources, silicon is to be preferred over gallium, since it is far more abundant and cheaper.…”