A ZrO 2 —Al 2 O 3 composite ceramic material having high mechanical strength and toughness as well as excellent wear resistance and hardness is provided. This ceramic material includes a first phase of ZrO 2 grains containing 10 to 12 mol % of CeO 2 as a stabilizer and having an average grain size of 0.1 μm to 1 μm, and a second phase of Al 2 O 3 grains having an average grain size of 0.1 to 0.5 μm. The ceramic material has a mutual nano-composite structure formed under a condition that a content of the second phase in the ceramic material is within a range of 20 to 60 vol % such that the Al 2 O 3 grains are dispersed within said ZrO 2 grains at a first dispersion ratio of 2% or more, and preferably 4% or more, which is defined as a ratio of the number of the Al 2 O 3 grains dispersed within the ZrO 2 grains relative to the number of the entire Al 2 O 3 grains dispersed in the ceramic material, and the ZrO 2 grains are dispersed within the Al 2 O 3 grains at a second dispersion ratio of 1% or more, which is defined as a ratio of the number of the ZrO 2 grains dispersed within the Al 2 O 3 grains relative to the number of the entire ZrO 2 grains dispersed in the ceramic material.
1. A method of producing a ZrO 2 —Al 2 O 3 composite ceramic material, said composite ceramic material comprising:
a first phase of ZrO 2 grains containing 10 to 12 mol % of CeO 2 as a stabilizer and having an average grain size of 0.1 μm to 1 μm, said ZrO 2 grains composed of 90 vol % or more of tetragonal ZrO 2 ;
a second phase of Al 2 O 3 grains having an average grain size of 0.1 to 0.5 μm;
wherein said Al 2 O 3 grains are dispersed within said ZrO 2 grains at a first dispersion ratio of 4% or more, which is defined as a ratio of the number of said Al 2 O 3 grains dispersed within said ZrO 2 grains relative to the number of the entire Al 2 O 3 grains dispersed in the composite ceramic material, and
said ZrO 2 grains are dispersed within said Al 2 O 3 grains at a second dispersion ratio of 1% or more, which is defined as a ratio of the number of said ZrO 2 grains dispersed within said Al 2 O 3 grains relative to the number of the entire ZrO 2 grains dispersed in the composite ceramic material,
wherein the method comprises:
mixing an α-Al 2 O 3 powder having an average particle size of 0.3 μm or less with a γ-Al 2 O 3 powder having a specific surface within a range of 10 to 100 m 2/ g and a substantially spherical shape prepared such that a mixture ratio by volume of the γ-Al 2 O 3 powder to the α-Al 2 O 3 powder is in a range of 50:50 to 90:10, thereby obtaining a second powder for providing said Al 2 O 3 grains;
mixing a first powder for providing said ZrO 2 grains with the second powder;
molding a resultant mixture in a desired shape to obtain a green compact, and sintering said green compact at a sintering temperature in an oxygen-containing atmosphere.
2. The method as set forth in claim 1 , wherein said resultant mixture is calcined at a temperature of 800° C. or more and less than said sintering temperature, and then pulverized to obtain a calcined powder, and wherein said green compact of the calcined powder is sintered in the oxygen-containing atmosphere.