YAG (yttrium aluminum garnet, Y3Al5O12) powders were synthesized by a mechanochemical solid reaction of Y2O3 with AlOOH and γ-Al2O3. Phase development of the resultant YAG samples during grinding and calcination was compared between two types of aluminum source. The reaction of Y2O3 with AlOOH was activated by mechanical energy and the use of fine powder instead of heat energy, leading to the direct formation of YAG without second phases such as YAP (yttrium aluminum perovskite, YAlO3) and YAM (yttrium aluminum monoclinic, Y4Al2O9) with calcination at 800oC. However, the sample containing g-Al2O3 and Y2O3 yielded YAP along with YAM after calcination at 900oC because g-Al2O3 transformed into α-Al2O3, which made it difficult to diffuse Al3+ into Y2O3 lattice, and then by increasing temperatures to 1300oC, a wellcrystallized phase of pure YAG was obtained. YAG powders showed good sinterability, although the samples were hardly agglomerated after grinding. After the same calcination of two samples at 1000oC, YAG samples containing the AlOOH and γ-Al2O3 were densified to ~96.7 and ~92.9% of the theoretical density, respectively, by sintering at 1600oC for 4 h under atmospheric conditions. It is concluded that the use of a fine, type of starting materials and grinding time are believed to be important factors in the mechanochemical synthesis of YAG.

Keywords: YAG, Synthesis, Phase formation, Transition alumina, Sintering