Preparation and microstructure of polycrystalline Al2O3–YAG composites

Polycrystalline Al2O3–YAG composites were obtained from the powder prepared by a co-precipitation method. After the calcination at different temperatures, the crystallization of YAG was found at about 1000°C. Dense sintering bodies could be obtained by hot-press sintering at 1550°C. Bending strength and fracture toughness of Al2O3–5 vol.% YAG and Al2O3–25 vol.% YAG composites were 604 MPa and 5.0 MPa m1/2, 611 MPa and 4.5 MPa m1/2 respectively. It indicated that the incorporation of YAG benefited to the mechanical property improvement of Al2O3 ceramics. TEM observation revealed that large YAG particles (about 1 μm) located on the grain boundaries of Al2O3, and some small YAG particles (100–200 nm) were inside Al2O3 grains in both composites. Many white areas were found in Al2O3–5 vol.%YAG composite, which probably results from low concentration of yttrium.