A series of phase-pure [(Gd 0.6 Lu 0.4 ) 0.99 Ce 0.01 ] 3 [Al 1- z (Mg/Si) z ] 5 O 12 ( z = 0-0.10) garnet phosphor powders were prepared via gel-combustion, which were then sintered into ceramics (up to 1550 °C) under atmospheric pressure. Dilatometry revealed that equimole of Mg 2+ /Si 4+ substitution for Al 3+ accelerates densification and lowers the activation energy for grain boundary diffusion in the intermediate stage of sintering (∼1150–1370 °C), which was assayed to be ∼353 kJ/mol for z = 0 and ∼289 kJ/mol for z = 0.10. The acceleration effects of Mg 2+ /Si 4+ on sintering and grain growth were further demonstrated by the results of ramp and holding sintering. Firing at 1550 °C for 4 h also produced ∼99 % dense ceramics for the Mg 2+ /Si 4+ codoped garnet powders. Through considering crystal splitting of the Ce 3+ 5d energy level, photon-phonon coupling, and crystal structure/microstructure, the influences of Mg 2+ /Si 4+ content and material form on Ce 3+ luminescence, including intensity, external/internal quantum efficiencies, emission wavelength, CIE color coordinates and decay time, were clarified in detail.
Enbei Yang,Han Ma,Qiang Zhou,Mengyan Yang,Yurong Guo,Jing Wan,Huaijun Tang,Zhengliang Wang
The luminescence enhancement of near-infrared (NIR) emissive material is critical in emerging applications. In this work, we have prepared an NIR-emitting K 2 NaSc 1- x - y Al x F 6 : y Cr 3+ (denoted as KNS 1- x - y A x F: y Cr) solid solution phosphor via the introduction of Al 3+ , enhancing luminescence in a high-temperature solid-state reaction. The resultant solid solution phosphor exhibited a broad NIR emission band with a high internal quantum efficiency (IQE = 81.1 %) and an enhanced photoluminescence thermal stability (93 % at 423 K) under 432 nm excitation. When compared with the Al-free sample, the IQE and thermal stability are increased by 45.9 % and 22.4 %, respectively. The optimal Cr 3+ and Al 3+ doping content has been determined and a composition-optimized KNS 0.70 A 0.25 F 6 :0.05Cr phosphor is demonstrated by fabricating an NIR pc-LED device as a light source for light-emitting diode applications.
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