The effect of precipitant on co-precipitation synthesis of yttrium aluminum garnet powders

Polycrystalline yttrium aluminum garnet (Y3Al5O12, YAG) powders were prepared by the co-precipitation method from a mixed solution of aluminum and yttrium nitrates (Y(NO3)3·6H2O, Al(NO3)3·9H2O) using ammonium carbonate ((NH4)2CO3, AC) and ammonium hydrogen carbonate (NH4HCO3, AHC) as precipitants. The effect of precipitant and pH on the preparation of pure-phase YAG powders was mainly studied. Phase evolution of the precursors during calcination and sinterability of the resultant YAG powders were compared for the two precipitants. The composition of YAG precursor, the phase formation process of YAG and the properties of the powders were investigated by means of DTA–TG, XRD, and TEM. AC as precipitant could produce a hydroxide precursor, which transformed to a YAG and Y2O3 mixture at about 1300 K. AHC as precipitant could produce a loosely agglomerated carbonate precursor. The resultant YAG powders showed good dispersity and excellent sinterability. The precursor directly converted to pure YAG via YAlO3 (YAP) phase at about 1300 K.