Stoichiometric yttrium aluminate garnet (Y3Al5O12) precursors with a wide range of chemical compositions were precipitated by dripping a mixed solution of ammonium aluminum sulfate and yttrium nitrate into ammonium bicarbonate solutions. The resultant precursors were characterized by chemical analysis, infrared spectroscopy, differential thermal analysis/thermogravimetry, x-ray diffractometry, and scanning electron microscopy. The effects of reaction temperature, precipitant concentration, dripping speed of the salt solution, and the molar ratio of precipitant/total-cations on the composition, thermal behavior, and particle morphology of the resultant precursors were investigated. The precipitation conditions that yield carbonate precursors composed of ammonium dawsonite [NH4Al(OH)2CO3] and yttrium normal carbonate [Y2(CO3)3 · 3H2O] were determined.