The Non-Concentration-Quenching Phosphor Ca₃Eu₂B₄O₁₂ for WLED Application

Abstract

Commercial white LED devices usually suffer from a high color temperature and poor color rendering. Developing a new, efficient, and stable red phosphor is the key to solving this problem. In this work, a series of pure Ca3Y2‑xB4O12:xEu3+ (0 < x ≤ 2) samples, including the new and fully transitional borate phosphor Ca3Eu2B4O12 (CEBO), have been successfully prepared by solid-state reaction synthesis. CEBO is isostructural with Ca3Y2B4O12 (CYBO), belonging to the orthorhombic system with space group Pnma (No. 62). Under optimal 393 nm excitation, this borate exhibits a strong red emission, peaking at 615 nm, with high color purity. Interestingly, the luminescence of CEBO is relatively higher than that of CYBO:Eu3+ phosphors. The quantum yield of this non-concentration-quenching phosphor reaches 95.6%. Furthermore, a warm pc-WLED device has been fabricated by mixing as-prepared CEBO powders and commercial BaMgAl10O17:Eu2+ and (Sr, Ba)2SiO4:Eu2+ phosphors, which exhibits a high color rendering index (Ra = 83.7) along with a color temperature of around 3883 K. The present work indicates that this new borate, with outstanding quantum efficiency and favorable thermal stability, can be used as a red phosphor for application in WLEDs.

Delayed Concentration Quenching of Luminescence Caused by Eu3+-Induced Phase Transition in LaSc3(BO3)4

“…As presented in Figure , most of the reported Eu 3+ -doped phosphors are located in the green rectangle, with the QE of 60%–85% and the remained fluorescent intensity of 70%–85% at 400 K compared with the initial intensity at room temperature (for details, see Table S5, Supporting Information). ,,,,,− In order to further improve the fluorescent performances, more research studies have been conducted, such as K 2 Tb­(PO 4 )­(WO 4 ):Eu 3+ with better thermal stability and Ca 3 Y 2 B 4 O 12 :Eu 3+ and Ca 4 LaO­(BO 3 ) 3 :Eu 3+ with higher quantum efficiencies. ,, However, the enhancement in only one aspect cannot meet the requirements of practical applications. The LSBO:0.8Eu 3+ phosphor in this work with a higher QE and a more excellent thermal performance not only jumps out of the rectangle but also locates at a better position in Figure .…”

“…An alternative strategy is finding quenching-free phosphors in appropriate hosts. A higher amount of Eu 3+ in the crystal cell is expected to have more absorption, and thus, numerous highly Eu 3+ -doped phosphors have been reported, for example, Ca 8 MgLu­(PO 4 ) 7 :Eu 3+ , Ba 6 Gd 2 Ti 4 O 17 :Eu 3+ , Ca 3 Y 2 B 4 O 12 :Eu 3+ , and so on. − Being different from those cases, a polymorphism compound LaSc 3 (BO 3 ) 4 (LSBO) is selected for Eu 3+ in this work. − We find that there always are two phases, a monoclinic α-LSBO and a trigonal β-LSBO, coexisting and constantly changing with different concentration of Eu 3+ doping. The phase transition induced by the doping concentration of the activator and the changes of luminescent properties caused by the transition are then studied in detail.…”

“…As shown in Figure 8, when the Eu 3+ concentration increases from 0.1 to 0.8 accompanied with α-LSBO continuously transforming to β-LSBO, there are reductions in the number of peaks at around 610 and ∼1300 cm −1 , corresponding to the vibrations of La−O and B−O on [BO 3 ] plane triangles, respectively. 31,51,52 In other words, the number of vibrational modes in β-LSBO is much less. Because of the strong correlation between the two vibrations of La−O and B−O, the O atoms, which are a part of the triangular plane [BO 3 ], simultaneously coordinated with La, are locked as targets.…”

Novel double‐perovskite Mg2InSbO6:Sm3+ phosphor with excellent heat‐resistant performance and high color purity used in white LEDs

“…Therefore, the greater the E a is, the more difficult the crossover process to occur. The following equation is used to calculate the activation energy (E a ), which can be used to confirm the thermal quenching mechanism of Mg 2 InSbO 6 :Sm 3+ samples 41 :…”

Efficient red and broadband near‐infrared luminescence in Mn2+/Yb3+‐doped phosphate phosphor

“…Therefore, many researchers are committed to developing red phosphors with excellent properties. There are some reports on red emitters, such as Sr[LiAl 3 N 4 ]:Eu 2+ , 10 CaAlSiN 3 :Eu 2+ , 25 Sr 2 [MgAl 5 N 7 ]:Eu 2+ , 26 Sr 2 Si 5 N 8 :Eu 2+ , 9,27 Rb 3 YSi 2 O 7 :Eu 2+ , 15 Sr 3 Ga 4 O 9 :Bi 3+ , 28 ZnWO 4 :Bi 3+ , 29 Ca 3 Y 2‑x B 4 O 12 :xEu 3+ 30 M 9 MnLi(PO 4 ) 7 (M = Ca, Sr), 31,32 and K 2 SiF 6 :Mn 4+ 33 …”