Combustion synthesis of YAG:Ce phosphors via the thermite reaction of aluminum

Abstract

Cerium-doped yttrium aluminum garnet (YAG:Ce) as a yellow phosphor for white light-emitting diodes (LEDs) was synthesized via a facile combustion method using Y 2 O 3 , CeO 2 , Al 2 O 3 , Al, and NaClO 4 as raw materials. The combustion synthesis approach utilizes the strong exothermic oxidation of aluminum to realize a self-sustaining reaction. In this study, we investigated the effects of the ratios of Al 2 O 3 to Al, fluxes, and coprecipitated materials as raw materials on the luminescence properties of the synthesized YAG:Ce phosphors. When the amount of Al 2 O 3 x was varied, the combustion reaction proceeded at x ≤ 1.8, with x = 1.725 being the optimum condition for producing a high-performance product. When 5 mass% BaF 2 was added, the luminescence intensity was significantly improved owing to a decrease of YAP (YAlO 3) formation with improved uniformity. However, the addition of CaF 2 and NaF did not improve the luminescence properties. To suppress the segregation of CeO 2 , we used the coprecipitated material Y 2 O 3-CeO 2 as a raw material. Unlike with separate addition of Y 2 O 3 and CeO 2 , Ce ions were uniformly distributed in the coprecipitated material, resulting in improved luminescence properties. The combination of BaF 2 and coprecipitated material significantly improved the internal quantum efficiency to 83.0%, which

Combustion Synthesis of Eu,Si-doped AlN Phosphor

“…白色 LED は，長寿命，高発光効率といった特徴から環 境への負荷が小さく，従来の照明源からの置き換えが進 んでいる。白色 LED は ， 青色 LED と Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+ ) [1,2]などの黄色蛍光体との組み合わせにより 疑似白色光を得る方式が一般的であるが，演色性を向上 させるため，青色 LED に赤色や緑色蛍光体を組み合わせ る方式や，紫色 LED に赤色，緑色，青色蛍光体を組み合 わせる方式が開発されている。用途に応じたさまざまな 特性を持つ蛍光体が開発されているが，中でも Ca-α-SiAlON:Eu 2+ 黄色蛍光体 [3][4][5][6][7][8]や，β-SiAlON:Eu 2+ 緑色蛍光 体 [4,6,9,10] Excitation Emission…”

YAG:Ce3+ Phosphor: From Micron-Sized Workhorse for General Lighting to a Bright Future on the Nanoscale

“…Both observations are a clear indication that Ce is not homogeneously distributed over the particles and suggest that CeO 2 particles form (doping concentrations of 1–5% are generally too low to be detected for elemental maps, as visible in Figure A, Ce map). It should be noted that dopant segregation is also known to occur in microcrystalline YAG:Ce, YAG:Ce single crystals, , and ceramics , but seems absent in microcrystalline YAG:Ce made via the solid state diffusion method, possibly because of the long reaction times at high temperature, which allow full diffusion of ions (often even further enhanced by the use of fluxes). An in-depth investigation in the Ce distribution over YAG nanocrystals would definitely add to the scientific literature, for example by NMR which was recently reported as a valuable tool for micron-sized phosphor crystals, , but also EPR-ENDOR techniques could give useful new insights.…”

Express Synthesis of YAG:Ce Ceramics in the High-Energy Electrons Flow Field

“…The developed synthesis methods, sol-gel [ 5 , 6 ], hydrothermal [ 7 ], and others, do not relieve the need for a long-term high-temperature treatment to form a phosphor powder with the desired structure and morphology and a purification from the substances used. The combustion method [ 8 , 9 ] provides the possibility of a rapid synthesis, but the need for a subsequent purification from residues of combustible materials requires annealing at high temperatures.…”