Template-free Synthesis and Characterization of Spherical Y₃Al₅O₁₂:Ce³⁺(YAG:Ce) Nanoparticles

Abstract

Cerium-activated yttrium aluminate (Y 3 Al 5 O 12 :Ce 3+ ) exhibiting a garnet structure has been widely utilized in the production of light emitting diodes (LEDs) as a yellow emitting phosphor. The commercialized yttrium aluminum garnet (YAG) phosphor is typically synthesized by a solid-state reaction, which produces irregular shape particles with a size of several tens of micrometers by using the top-down method. To control the shape and size of particles, which had been the primary disadvantage of top-down synthetic methods, we synthesized YAG:Ce nanoparticles with a diameter of 500 nm using a coprecipitation method under the atmospheric pressure without the use of template or special equipment. The precursor particles were formed by refluxing an aqueous solution of the nitrate salts of Y, Al, and Ce, urea, and polyvinylpyrrolidone (55 K) at 100 °C for 12 h. YAG:Ce nanoparticles were formed by the calcination of precursor particles at 1100 °C for 10 h under atmospheric conditions. The phase identification, microstructure, and photoluminescent properties of the products were evaluated by X-ray powder diffraction, scanning electron microscopy, absorption spectrum and photoluminescence analyses.

Synthesis and characterization of YAG:Ce phosphors for white LEDs

“…The thermal treatment can be done at atmospheric pressure or under different values of pressure (i.e., 10 -3 Pa, vacuum condition). Fluxes such as NaOH, BaF 2 , H 3 BO 3 /BaF 2 /hexa− methylenetetramine, YF 3 , Li 2 CO 3 , NaF, NH 4 NO 3 , SiO 2 , etc., are added to obtain greater crystallinity and to decrease grain size at lower the sintering temperature [6,21,[34][35][36][37]. A Ce 3+ concentration of 0.01-10 mol% can be used.…”

“…Also some studies show that the starting oxides are present up to a specific temperature (i.e., Al 2 O 3 to 1600°C) [26,38]. Y(CH 3 COO) 3 [4,36,41].…”

“…By using an autoclave for precipitate producer (in hydrothermal condi− tions) solvothermal (co)precipitation method can be sped up. Some possible reactions, which may be involved in the (co)precipitation process for YAG:Ce and YAG:Ce, Re synthesis are presented below [23,36,39,[42][43][44] It is important to keep a constant pH value, which can be done by adding the precipitation agent in excess or by con− trolling the dropwise time of the raw material solution over the precipitant solution. The variation in pH and the concen− tration of [NH 4 + ] and [CO 3 2-] influence the final product.…”

“…Average crystallite size of the YAG:Ce and YAG:Ce, Re powders, obtained by the methods presented above, was reported to be 20-100 nm (estimated using Scherrer's equa− tion, Dhkl=kl/bcosq, where D is the average grain size, k is the dimensionless shape factor -Scherrer's constant, l is the X−ray wavelength, b is the full width at half maximum intensity (FWHM) -expressed in radians, q is the Bragg dif− fraction angle) [23,27,36,48].…”