Synthesis and sintering of YAG powder by a mechanochemical solid reaction of yttria with two types of Aluminum source

Synthesis and sintering of YAG powder by a mechanochemical solid reaction of yttria with two types of Aluminum source

YAG (yttrium aluminum garnet, Y₃Al5O₁₂) powders were synthesized by a mechanochemical solid reaction of Y₂O₃with 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.

YAG (yttrium aluminum garnet, Y₃Al5O₁₂) powders were synthesized by a mechanochemical solid reaction of Y₂O₃with 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.