Abstract: Ni coated α-Al₂O₃ composite microspheres are first synthesized by heterogeneous precipitation coating method, and then Al₂O₃/Ni cermets are prepared by hot presssintering of the asprepared Ni-coated α-Al₂O₃ powders. The microstructural features of the resultant Al₂O₃Ni cermets and the crystalline phases of precipitated precursors, reduced powders and sintered cermets are characterized by scanning electron microscope(SEM), energy dispersive spectroscopy(EDS), and X-ray diffractometer (XRD). The relative densities of cermets are measured by Archimedes’ method, and the flexural strength and fracture toughness are estimated by the threepoint bending and single-edgenotched beam methods. The results exhibit that the Ni-doping activated the sintering of α-Al₂O₃, and Ni particles are uniformly distributed at the interface of alumina grains, which increase the weak interfaces, and enhance the fracture toughness of alumina, achieving a maximum value of
7.62 MPa·m^1/2.

Key words: Ni coated α-Al₂O₃ composite microsphere, Al₂O₃/Ni cermet, heterogeneous precipitation coating method, hot press-sintering, weak interface