Synthesis and Characterization of YAG Nanoparticles by Ultrasound‐Assisted and Ultrasound‐Microwave‐Assisted Alkoxide Hydrolysis Precipitation Methods

Abstract

Yttrium aluminum garnet (YAG, Y3Al5O12) nanoparticles were synthesized by ultrasound-assisted and ultrasound-microwave-assisted alkoxide hydrolysis precipitation methods. The effect of reaction parameters including pH value, ultrasonic radiation time, and calcination temperature on the composition of the products was investigated. The YAG nanoparticles and their precursor were characterized by X-ray powder diffraction (XRD), differential thermal analysis (DTA), Fourier-transform infrared spectroscopy (FT-IR), and high-resolution transmission electron microscopy (HRTEM). The results show that the single ultrasound-assisted method to synthesize YAG phase often contains intermediate phases of YAM (Y4Al2O9) and YAP (YAlO3); pure YAG phase can form only at special conditions and as single crystal. The pure phase YAG powders can be obtained at each experimental condition when using ultrasound-microwave-assisted synthesis and the grain is polycrystalline. This is due to the microwave radiation which promotes atomic diffusion and forms a lot of crystal nuclei of YAG in the precursor. The YAG nanoparticles with a grain size of 18 nm can be obtained at a calcination temperature of 900°C when using ultrasound-microwave-assisted method.

Garnet-Type Nanophosphors for White LED Lighting

“…To reduce even more the agglomeration of YAG:Ce NCs, surfactants, such as steric stabilizers (polyethylene glycol, PEG10000), electric stabilizers [(NH 4 ) 2 SO 4 , C 12 H 25 SO 4 Na], or other dispersing agents (e.g., graphene oxide nanosheets) (Li and Wang, 2009;Wang et al, 2009;Zhang and Yu, 2009;Que et al, 2017;Ji et al, 2018) were involved in the initial solutions, resulting after ∼1,000 • C calcination in nanoYAG (about 70 nm) with narrow particle size distribution, spherical shapes, moderate NC agglomeration, and enhanced PL emission intensity. With no surfactant but by combining ultrasonication during the addition of the initial solution to the precipitant and microwave heating, Si et al managed to produce uniformly dispersed 18 nm (900 • C) to 43 nm (1,100 • C, Figure 1B) YAG particles depending on the annealing temperature, with reduced agglomeration (Si et al, 2014). Very recently, Gaiser et al published an original two-step approach, including first the formation of particles in ionic liquid solution, followed by a heat-treatment at 600 • C to crystallize YAG:Ce NCs embedded in a LiCl matrix, preventing their agglomeration.…”

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“…, YAH transforms to YAP due to the affinity of oxygen for different solute atoms, and finally, Al [31,32]. The volume fraction relationship for the four particle types (YAG > YAP > YAH > YAM) may be explained by this formation sequence, which may due to the sintering process at 1200 • C and excess oxygen.…”

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“…Hakuta et al [42] Ultrasound microwave-assisted -Aggregated particles with a grain size of 18 nm Si et al [54] Sonochemical -Aggregated nanoparticles with an average size of 22…”