A ZrO 2 —Al 2 O 3 composite ceramic material having excellent wear resistance, hardness, strength and toughness is provided. This ceramic material comprises a ZrO 2 phase composed of 90 vol % or more of tetragonal ZrO 2 , and containing 10 to 12 mol % of CeO 2 as a stabilizer, and an Al 2 O 3 phase. An amount of the Al 2 O 3 phase in the ceramic material is in a range of 20 to 70 vol %, and preferably 40 to 70 vol %. In the composite ceramic material, Al 2 O 3 grains each having a fine ZrO 2 grain therein are dispersed. Some of the Al 2 O 3 grains each having the fine ZrO 2 grain therein are trapped within ZrO 2 grains to form composite grains. A ratio of the number of the Al 2 O 3 grains each having the fine ZrO 2 grain therein relative to the number of the entire Al 2 O 3 grains dispersed in the composite ceramic material is 10% or more, and preferably 50% or more.
1. A ZrO 2 —Al 2 O 3 composite ceramic material comprising a ZrO 2 phase containing 10 to 12 mol % of CeO 2 as a stabilizer and composed of 90 vol % or more of tetragonal ZrO 2 , and an Al 2 O 3 phase,
wherein an amount of said Al 2 O 3 phase in the composite ceramic material is in a range of 40 to 70 vol %,
Al 2 O 3 grains each having a fine ZrO 2 grain therein are dispersed in the composite ceramic material,
some of the Al 2 O 3 grains each having the fine ZrO 2 grain therein are trapped within ZrO 2 grains to form composite grains,
a first dispersion ratio defined as a ratio of the number of the Al 2 O 3 grains each having the fine ZrO 2 grain therein relative to the number of the entire Al 2 O 3 grains dispersed in the composite ceramic material is 50% or more, and
a second dispersion ratio defined as a ratio of the number of the Al 2 O 3 grains of said composite grains relative to the number of the entire Al 2 O 3 grains dispersed in the composite ceramic material is 0.3% or more.
2. The composite ceramic material as set forth in claim 1 , wherein ZrO 2 grains each having an Al 2 O 3 grain therein are dispersed in the composite ceramic material,
a third dispersion ratio defined as a ratio of the number of the Al 2 O 3 grains trapped within the ZrO 2 grains relative to the number of the entire Al 2 O 3 grains dispersed in the composite ceramic material is 1.5% or more, and
wherein the second dispersion ratio “R2” is 0.6% or more, and
wherein the second dispersion ratio “R2” satisfies the following condition:
R 2 ≧α×R 3 ×R 1/100
wherein “R1” is the first dispersion ratio, “R3” is the third dispersion ratio, and “α” is a coefficient determined within a range of 0.8 to 1 by taking account of measurement errors.
3. A method of producing the ZrO 2 —Al 2 O 3 composite ceramic material as set forth in claim 1 comprising the steps of:
mixing a first powder for providing said ZrO 2 phase with a second powder for providing said Al 2 O 3 phase such that an amount of said Al 2 O 3 phase in the composite ceramic material is in a range of 40 to 70 vol %;
molding a resultant mixture in a desired shape to obtain a green compact; and
sintering said green compact in an oxygen-containing atmosphere,
wherein the second powder contains Al 2 O 3 particles each having a fine ZrO 2 particle therein,
wherein some of the Al 2 O 3 particles each having the fine ZrO 2 particle therein becomes trapped within ZrO 2 particles to form composite grains,
wherein a ratio of the number of the Al 2 O 3 particles each having the fine ZrO 2 particle therein relative to the number of entire Al 2 O 3 particles dispersed in the composite ceramic material is 50% or more, and
wherein a ratio of the number of the Al 2 O 3 particles of said composite grains relative to the number of the entire Al 2 O 3 particles dispersed in the composite ceramic material is 0.3% or more.
4. The method as set forth in claim 3 , wherein a preparation process of the second powder comprises the step of adding a ZrO 2 powder to at least one selected from a θ-Al 2 O 3 powder and a γ-Al 2 O 3 powder having a specific surface area of 50 to 400 m 2 /g to obtain a mixed powder.
5. The method as set forth in claim 3 , wherein a preparation process of the second powder comprises the steps of adding a ZrO 2 powder to one of an aqueous solution of an aluminum salt and an organic solution of an aluminum alkoxide, hydrolyzing a resultant mixture to obtain a precipitate, and drying the precipitate.
6. The method as set forth in claim 3 , wherein a preparation process of the second powder comprises the steps of adding an aqueous solution of a zirconium salt to one of an aqueous solution of an aluminum salt and an organic solution of an aluminum alkoxide, hydrolyzing a resultant mixture to obtain a precipitate, and drying the precipitate.
7. The method as set forth in claim 4 , comprising the step of calcining the mixed powder in an oxygen containing atmosphere at a temperature of 800° C. to 1300° C.
8. The method as set forth in claim 5 , comprising the step of calcining the precipitate in an oxygen containing atmosphere at a temperature of from 800° C. to 1300° C.
9. The method as set forth in claim 6 , comprising the step of calcining the precipitate in an oxygen containing atmosphere at a temperature of from 800° C. to 1300° C.
10. The method as set forth in claim 3 , wherein a volume ratio of Al 2 O 3 :ZrO 2 in the second powder is in a range of 95:5 to 50:50.
11. The composite ceramic material as set forth in claim 1 , wherein ZrO 2 grains each having an Al 2 O 3 grain therein are dispersed in the composite ceramic material,
a third dispersion ratio defined as a ratio of the number of the Al 2 O 3 grains trapped within the ZrO 2 grains relative to the number of the entire Al 2 O 3 grains dispersed in the composite ceramic material is 1.5% or more.