Synthesis And Photoluminescence Properties Of YAG:Ce³⁺, Ln³⁺ And YAG:Eu³⁺ Ultra-Fine Phosphors

In this paper, we briefly illustrated the luminescence theory of WLED. And the development and synthesis methods of phosphors were introduced too. In addition, the luminescence properties of rare-earth were reviewed. The progress in the field of YAG: Ce³⁺, Ln³⁺ (Ln=Pr³⁺, Eu³⁺) and YAG: Eu³⁺ materials were also summarized.YAG: Ce³⁺, Ln³⁺ (Ln=Pr³⁺, Eu³⁺) and YAG: Eu³⁺ phosphors were prepared by co-precipitation method and micelle-assisted co-precipitation method. The structure, morphology and luminescent properties of the powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and photoluminescence method. Generally, YAG: Ce³⁺, Ln³⁺ (Ln=Pr³⁺, Eu³⁺) is used to assemble the White Light Emitting Diode (WLED). YAG: Eu³⁺ is excellent red-phosphor and has attracted a great deal of interest for use in cathode ray tubes, high-pressure fluorescent mercury lamps and plasma display panels (PDP).The precursor was prepared via a co-precipitation method using NH4HCO3 solution as the precipitator. Then, Y2.94-xCexPr0.06Al5O12 (YAG: Ce³⁺, Pr³⁺) powders were obtained by calcining the precursor at 1200°C for 3 hours in argon atmosphere. The as-calcined powder is a body-center cubic Y3Al5O12: Ce³⁺, Pr³⁺ phase. YAG: Ce³⁺, Pr³⁺ particles were agglomerated and coral-like in shape. The excitation spectra of YAG: Ce³⁺, Pr³⁺ powders consist of three excitation bands at 290 nm, 342 nm and 450-470 nm, respectively. When excited with a ultraviolet light of 290 nm, the YAG: Ce³⁺, Pr³⁺ powders showed four emission bands at 386 nm, 489 nm, 535 nm and 612 nm. However, when excited with a blue light of 460 nm, the YAG: Ce³⁺, Pr³⁺ powders showed two emission bands at 535 nm and 612 nm. The energy transfer between Ce³⁺ and Pr³⁺ in YAG: Ce³⁺, Pr³⁺ powders was discussed.The precursor was prepared via a co-precipitation method using NH4HCO3 solution as the precipitator. Then, YAG: Ce³⁺, Eu³⁺ powders were obtained by calcining the precursor at 1200°C for 3 hours in argon atmosphere. The as-calcined powder is a body-center cubic YAG: Ce³⁺, Eu³⁺ phase. The YAG: Ce³⁺, Eu³⁺ particles were agglomerated and coral-like in shape. The excitation spectra of YAG: Ce³⁺, Eu³⁺ powders consist of two excitation bands at 340 nm and 450-470 nm. When excited with a ultraviolet the lights of 460 nm and 342 nm, the YAG: Ce³⁺, Eu³⁺ powders showed only an emission bands at 530 nm. It was found that doping with Eu³⁺ in YAG: Ce the emission intensities of Ce³⁺ quenched strongly.YAG: Eu³⁺ precursors were prepared via a micelle-assisted co-precipitation method using cetyltrimethylammonium bromide (CTAB) as surfactant, 1-butanol and ethanol as the solubilizer of CTAB. YAG: Eu³⁺ powders were obtained after the precursors were sintered for 2 hours at 900°C and 1000°C in air atmosphere, respectively. XRD result indicated that the resultant powders at 900°C and 1000°C belong to cubic YAG: Eu³⁺ phase. TEM result indicated that the particle sizes were 50-70 nm, and that the particles were agglomerated into coral-like structure. The resultant YAG: Eu³⁺ powders can emit orange-red light.