YAG precursor was synthesized by a co-precipitation method from a mixed solution of aluminum and yttrium nitrates with aqueous ammonia as the precipitator. The structure, phase evolution and morphology of YAG precursor and the sintered powders were studied by means of IR, TG/DTA, XRD, TEM methods. It was found the precursor with approximate composition of Al(OH)(3)center dot 0.3[Y-2(OH)(5)center dot(NO3)(2)center dot 2H(2)O] directly transformed to pure-YAG phase at 800 degrees C and no intermediate phases were detected. YAG nanocrystalline powders from sintering the precursor at different temperatures were less-aggregated and the diameters of the grains were about 40-100 nm. BET surface area of the particles decreased with increase of calcination temperature and the powder sintered at 800 degrees C can be used for fabrication of transparent YAG ceramics. (c) 2005 Elsevier Ltd. All rights reserved.