Preparation and Microstructure of Al_2O_3-YAG Composites

Polycrystalline Al_2O_3-YAG composites were obtained by using the coprecipitation method. After calcining at different temperatures, the crystallization of YAG was found at about 1000℃. Dense bodies could be got by hot-pressing at 1550℃. Bending strength and fracture toughness of Al2O3-5vol%YAG and Al2O3-25vol%YAG composites were 604 MPa and 5.0MPa.m1/2, 611MPa and 4.5MPa m1/2 respectively. It indicated that the incorporation of YAG improved the mechanical property of A12O3 ceramics. Through TEM observation, large YAG particles (about 1mm) located on the grain boundaries of Al2O3 were seen, and some small YAG particles (100~200nm) was among Al2O3 grains in both composites. A lot of white areas were found in Al2O3-5vol% YAG composite, which maybe result from the low concentration of yttrium.