Preparation and Mechanical Properties of Pressureless Sintered Al_2O_3 Ceramics with Submicrometer Grains

Al2O3ceramics with submicrometer grains were fabricated by pressureless sintering method,using high purityα-Al2O3 powders as starting material and MgO-Y2O3 as additive.The effects of sintering temperature and additive on densification process,microstructure and mechanical properties of Al2O3 were studied.The results show that the addition of MgO-Y2O3 additive could promote the densification,refine the microstructure and improve the mechanical properties of Al2O3.Submicrometer Al2O3 ceramics with relative density of 99.6% and average grain size of about 0.71μm can be obtained by sintering at 1450℃for 1h.The Vickers hardness and fracture toughness are 18.5GPa and 4.6 MPa·m1/2,respectively.