Effects of Milling and Calcination Temperature on the Compressibility and Sinterability of a Nanocrystalline Al2O3-Y3Al5O12 Composite Powder

In the present work, the effects of milling and calcination temperature on the compressibility and sinterability of a nanocrystalline Al2O3-Y3Al5O12 composite powder prepared by an aqueous sol-gel method were investigated. The results showed that calcination temperature has a strong influence on the sinterability and final microstructure of amorphous powders. The lower calcination temperatures below 800 degrees C resulted in the reduction of density and formation of a vermicular microstructure after sintering. It was also found that breaking of hard agglomerates into particles and smaller agglomerates after 1 h of milling leads to an increase in green density at the early stage of compaction when the rearrangement of particles is the dominant mechanism of the densification. The best-performing sample was that calcined at 800 degrees C and milled for 1 h, which yielded a relative density of 95% with a micronic/sub-micronic microstructure after sintering at 1500 degrees C.