Sintered alumina-based ceramics and process for producing same
AssigneeNgk Spark Plug Co., Ltd.
InventorsHiroshi Yamamoto, Satoshi Iio
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Abstract
Alumina-based ceramics are thermally stable because of their high melting point and excellent materials in wear resistant properties and chemical stability. However, they contradictly have such a problem that fracture toughness is low, and its improvement is desired. The present invention provides such sintered alumina-based ceramics and their production process that have rendered to grow alumina grains anisotropically and fracture simultaneously attain high flexural strength and fracture toughness by sintering the formed mixture comprising Al2O3, 0.05-2.5 mol % of VA metal oxide and 0.01-4 mol % SiO2, relative to Al2O3, respectively.
Claims22
A sintered ceramic comprising a matrix phase of anisotropic alumina grains which are grown anisotropically and a grain boundary phase, said grain boundary phase comprising alumina, an oxide of a group VB element and SiO2, said sintered ceramics having a flexural strength at room temperature of not less than 500 MPa and a fracture toughness of not less than 5 MPa m0.5, said sintered ceramics having been produced by forming a mixture comprising Al2O3, the oxide of the group VB element and said SiO2 and sintering the mixture at a temperature of 1,320 to 1,600° C., wherein said oxide of the group VB element is present in an amount of 0.05 to 2.5 parts by mol, and said SiO2 is present in an amount of 0.01 to 4 parts by mol, relative to 100 parts by mol of Al2O3, respectively.
A sintered-ceramic comprising alumina, an oxide of a VB group element and SiO2, wherein said alumina comprises anisotropically grown alumina grains, and said alumina is present in an amount exceeding 96% by weight of said sintered ceramics, said sintered ceramics having a flexural strength at room temperature of not less than 500 MPa and a fracture toughness of not less than 5 MPa m0.5 said sintered ceramics having been produced by forming a mixture comprising Al2O3, the oxide of the group VB element and SiO2 and sintering the formed mixture at a temperature of 1,320 to 1,600° C.
A sintered ceramic comprising a matrix phase of anisotropically grown alumina grains and a grain boundary phase, the grain boundary phase comprising alumina, a group VB element oxide and SiO2,
- wherein said anisotropically grown alumina grains are grown in a liquid phase during sintering, and said liquid phase forming said grain boundary phase, said sintered ceramics having a flexural strength at room temperature of not less than 500 MPa and a fracture toughness of not less than 5 MPa m0.5.
Dependencies are inferred from the claim text.