An yttrium aluminum garnet (YAG) precursor precipitate was synthesized by urea method using yttria (Y(2)O(3)) and aluminum nitrate (Al(NO(3))(3)center dot 9H(2)O) as raw materials. The fresh wet precipitate was dried by supercritical carbon dioxide (CO(2)) fluid and the resulting powder was calcined at temperatures from 600 to 1600 degrees C. Crystallization of YAG was detected at 800 degrees C, and completed at 900 degrees C. HRTEM images of the YAG product obtained above 900 degrees C revealed crystallographically specific oriented attachment along the [1 1 2] direction. Based on the observation of the particle morphology a possible growth mechanism of YAG nanoparticles was presented. The fast increase on the average crystallite size of YAG at temperatures from 900 to 1300 degrees C is attributed to the crystallographically specific oriented attachment growth process. As the growth process proceeds at higher temperatures, oriented attachment based growth becomes less important because of the increase on particle size, and the self-integration assisted by the Ostwald ripening becomes dominant. (C) 2010 Elsevier Ltd. All rights reserved.