Abstract: It is an object to provide an aluminum oxide-based sintered body and a manufacturing method thereof, according to which all of wear resistance, strength and fracture toughness can be exhibited to a high degree in a single sintered body, and there is provided a method of manufacturing a multi-layer aluminum oxide sintered body having high strength and wear resistance as well as high fracture toughness, that has a structure of at least two layers in which a surface layer is a high-strength wear-resistant layer comprising isometric crystals having a small grain size, and an inner part is a high-fracture-toughness layer constituted from anisotropic crystals, the method comprising the steps of (1) preparing a layered body by forming a layer of an aluminum oxide material that has a purity of at least 90% and contains a grain growth inhibiting agent and a layer of an aluminum oxide material that has a purity of at least 90% and contains a grain growth promoting agent, (2) carrying out setting such that the sintering

Abstract: This invention relates to highly toughened alumina sintered bodies, and the highly toughened alumina sintered bodies are fabricated by sintering an &agr;-aluminum oxide powder which is obtained by employing an aluminum hydroxide produced by the Bayer's process as a starting material, and calcining at 900-1200° C. a mixture obtained by adding abrasion powder worn from pulverizing alumina balls or another product to the material, in an amount of 0.01-20 mass % as seed crystals for &agr;-aluminum oxide.