Garnet-based Li₆CaLa₂Sb₂O₁₂:Eu³⁺red phosphors: a potential color-converting material for warm white light-emitting diodes

Abstract

To alleviate the issues of low thermal stability and high correlated color temperature, exploring an inorganic color converter with both yellow-and red-emissions to replace the conventional resin/silicone-based phosphor converter for obtaining high-power warm white light-emitting diodes is highly desired. In this study, a series of garnet-based Li 6 CaLa 2À2x Eu 2x Sb 2 O 12 (x = 0.1-1.0) red phosphors have been successfully synthesized by a conventional high-temperature solid-state method. The microstructure and luminescence properties were systematically investigated by X-ray diffraction, emission/excitation spectra, luminescence lifetimes and temperature-dependent decays. The as-synthesized phosphors exhibited a highly efficient red luminescence at 611 nm corresponding to the 5 D 0 -7 F 2 electric dipole transition of Eu 3+ , and the luminescence monotonously enhanced as the Eu 3+ content was increased to 100 mol%. The absence of concentration quenching was ascribed to the large Eu 3+ -Eu 3+ distance (7.048-7.105 Å) and subsequently the hindering of unwanted energy migration among them in the Li 6 CaLa 2 Sb 2 O 12 crystalline lattice. Impressively, the Li 6 CaLaEuSb 2 O 12 phosphor showed an excellent thermal stability with only 9.7% emission loss when the recording temperature was increased from 293 K to 553 K. To evaluate the suitability of Li 6 CaLa 2 Sb 2 O 12 :Eu 3+ as a red converter, both the garnet-based Y 3 Al 5 O 12 :Ce 3+ yellow and Li 6 CaLa 2 Sb 2 O 12 :Eu 3+ red phosphor co-doped glass ceramics were successfully fabricated by a low-temperature co-sintering technique.Importantly, the adverse energy transfers between Ce 3+ and Eu 3+ were efficiently suppressed due to the spatial separation of Ce 3+ in Y 3 Al 5 O 12 and Eu 3+ in Li 6 CaLa 2 Sb 2 O 12 in the crystal lattice. As a consequence, the quantum yield of the glass ceramic reached as high as 89.3%, and the constructed white light-emitting diode exhibited an optimal luminous efficacy of 101 lm W À1 , a correlated color temperature of 5449 K and a color rendering index of 73.7. It is expected that the developed Li 6 CaLa 2À2x Eu 2x Sb 2 O 12 red phosphors and the related glass ceramics should have potential applications in high-power warm white light-emitting diodes.

Glass Ceramic Phosphors: Towards Long‐Lifetime High‐Power White Light‐Emitting‐Diode Applications–A Review

“…Likewise, CaMg 2 Al 16 O 27 :Mn 4+ , YAG:Mn 4+ ,Mg 2+ , SrMgAl 10 O 17 :Mn 4+ ,Li + [ ] red phosphors are also demonstrated possessing good ability to tune the spectral property of YAG:Ce 3+ GC. The other interesting example is the partition of garnet‐based Li 6 CaLa 2 Sb 2 O 12 :Eu 3+ (LCLSO:Eu 3+ ) into glass host (Figure b) . LCLSO:Eu 3+ exhibits highly efficient red luminescence in absence of the concentration quenching.…”

“…c) CIE color coordinates of the GCs with various LCLSO:Eu 3+ contents (1‐15 wt%) and a fixed Ce:YAG content (3 wt%). Reproduced with permission . Copyright 2015, Royal Society of Chemistry.…”

A series of tunable emission phosphors of Sm3+, Eu3+ and Mn2+ doped Ba3Tb(PO4)3: luminescence and energy transfer

“…2,3 Generally, the trivalent europium (Eu 3+ ) ion has been recognized as an excellent activator in many red phosphors due to the 5 D 0 -7 F J(J=0, 1, 2, 3, 4) transitions of Eu 3+ . [4][5][6] For the Eu 3+ -doped phosphors, the excitation lines via the characteristic f-f transitions of Eu 3+ locate at ultraviolet region. However, in the region of 300-380 nm, Eu 3+ -doped phosphors have a weak absorption, thus, it is necessary to find a sensitizer for Eu 3+ luminescence.…”

Sol-gel synthesis and third-order optical nonlinearity of Au nanoparticles doped monolithic glass

“…The highly extensive focus and study on nanomaterials in all fields has maintained for decades [4,5]. Nanomaterials with great third-order optical nonlinearities and fast response time are significant for future optical device applications [6][7][8].…”