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Abstract Monodispersed alumina powders were prepared via nonaqueous precipitation process using aluminum powders as aluminum source, acetic acid as precipitant. Effect of oxygen donor and solvent alcohol such as methanol, ethanol, isopropanol on the preparation of ultrafine alumina powders and the precursor reaction mechanism have been investigated by XRD, FT-IR, TEM, FE-SEM and performance tests of sintered bodies. The intermolecular condensation of methanol with the catalysis of Lewis acid aluminum methoxide leads to hydrolysis of aluminum methoxide, forming amorphous precipitates, dehydration polycondensation of aluminum hydroxide and resulting in serious agglomeration of precipitates and alumina powders, the worst morphology and properties of sintered body. The pulling electron effect and steric hindrance of isopropyl group make the structure of aluminum isopropoxide overwhelmingly stable and relatively arduous to be replaced by precipitant acetic acid, which results in underdeveloped crystallinity and agglomeration of both precipitates and alumina powders, poor morphology and properties of sintered body. The optimized oxygen donor and solvent alcohol is ethanol. Monodispersed, high crystallinity C 4 H 7 AlO 7 precipitates and alumina powders can be obtained when ethanol is used as oxygen donor and solvent, and the highest relative density, mechanical properties and the most homogeneous microstructure was obtained. The density, flexural strength, volume resistivity, breakdown voltage and thermal expansion coefficient are 99.1% of TD, 128.0 ± 2.2 MPa, 9.8 × 1016 Ω∙cm, 45.2 kV/mm and 7.6 × 10−6 °C−1, respectively. Precursor reaction mechanism is deduced that aluminum powders react with oxygen donor alcohol to form aluminum alkoxide with the catalyst iodine, and then react with acetic acid to form crystal C 4 H 7 AlO 7 precipitates. Nonaqueous precipitation method is expected to become a promising candidate for mass production of alumina powders. [ABSTRACT FROM AUTHOR]

A monodispersed Al 2 O 3 @YAG: Ce core-shell phosphor has been synthesized by coating Y 2 O 3 : Ce film on Al 2 O 3 particle. The phosphor has particles size of 60–120 nm and shows high dispersity due to the high dispersed Al 2 O 3 particles prepared by nonaqueous precipitation method. The core-shell structured phosphor consists of a corundum core and a YAG shell. The Al 2 O 3 @YAG: Ce core-shell yellow phosphor presents high yellow emission. The light-emitting diode (WLED) based on this yellow phosphor and InGaN blue chip displays high white purity. This Al 2 O 3 @YAG: Ce core–shell phosphor can be viewed as a promising candidate yellow phosphor for white LEDs. [ABSTRACT FROM AUTHOR]