COMBUSTION SYNTHESIS OF FINE PARTICLE RARE-EARTH ORTHOALUMINATES AND YTTRIUM-ALUMINUM-GARNET

Fine particle rare earth orthoaluminates, LnAlO3, where Ln = La, Pr, Nd, Sm, Gd, Tb, and Dy, and yttrium aluminum garnet, Y3Al5O12 (YAG), have been prepared by a novel combustion process using corresponding rare earth nitrate, aluminum nitrate, and urea/carbohydrazide mixtures. A saturated aqueous solution of the mixture when rapidly heated at 500°C foams and ignites to yield voluminous, crystalline single phase rare earth orthoaluminates in less than 5 min. The solid combustion products were characterized by XRD, SEM, TEM, particle size analysis, and surface area measurements. Rare earth orthoaluminates obtained have 3-4 m2/g surface area, with particle size in the range of 0.1-0.6 μm and an average agglomerate size of 4-5 μm. © 1990.