Al.sub.2 O.sub.3 /ZrO.sub.2 ceramic
AssigneeRockwell International Corporation
InventorFrederick F. Lange
Life of this patent
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Abstract
Fracture toughness and strength of an Al.sub.2 O.sub.3 /ZrO.sub.2 ceramic is increased by incorporating metastable grains of tetragonal ZrO.sub.2 in the structure. During cracking, the metastable tetragonal ZrO.sub.2 transforms to a stable monoclinic structure thus increasing the energy required for the crack to propagate and retarding its growth. The ZrO.sub.2 occupies from 5 to 95% of the volume of the ceramic and has dissolved in it a rare earth oxide such as Y.sub.2 O.sub.3, CeO.sub.2, La.sub.2 O.sub.3 and/or Er.sub.2 O.sub.3 to promote retention of the metastable tetragonal ZrO.sub.2.
Claims9
A ceramic comprising:
- 5 to 95 v/o ZrO.sub.2 in the form of crystalline grains having a diameter less than about 2 .mu.m and a substantially tetragonal structure;
- a rare earth oxide selected from the group consisting of Y.sub.2 O.sub.3, CeO.sub.2, Er.sub.2 O.sub.3, and La.sub.2 O.sub.3, there being at least enough of said rare earth oxide to increase the amount of ZrO.sub.2 having a tetragonal crystal structure, but not enough of said rare earth oxide to form substantial amounts of said ZrO.sub.2 having a cubic crystal structure;
- and
- the remainder of said ceramic being substantially Al.sub.2 O.sub.3.
A ceramic comprising:
- 5-95 v/o ZrO.sub.2 in the form of grains having a diameter less than about 2 .mu.m;
- about 2 m/o Y.sub.2 O.sub.3 ;
- and
- 95 to 5 v/o Al.sub.2 O.sub.3, whereby said ZrO.sub.2 grains are substantially tetragonal in structure and said ceramic is free of ZrO.sub.2 grains having a cubic structure.
A ceramic comprising:
- 5 to 95 v/o ZrO.sub.2 in the form of grains having a diameter less than about 2 .mu.m and a sbstantially tetragonal structure;
- 0.5 to 5.5 m/o Y.sub.2 O.sub.3 ;
- and
- 95 to 5 v/o Al.sub.2 O.sub.3.
A ceramic comprising:
- 5 to 95 v/o ZrO.sub.2 in the form of grains having a diameter less than about 2 .mu.m and a substantially tetragonal structure;
- 0.5 to 10 m/o CeO.sub.2 ;
- and
- 95 to 5 v/o Al.sub.2 O.sub.3.
A ceramic comprising:
- 5 to 95 v/o ZrO.sub.2 in the form of grains having a diameter less than about 2 .mu.m and a substantially tetragonal structure;
- 0.4 to 4 m/o Er.sub.2 O.sub.3 ;
- and
- 95 to 5 v/o Al.sub.2 O.sub.3.
A ceramic comprising:
- 30 to 60 v/o ZrO.sub.2 in the form of grains having a diameter less than about 2 .mu.m and a substantially tetrogonal structure;
- about 2 m/o Y.sub.2 O.sub.3 ;
- and
- the remainder of said ceramic being substantially Al.sub.2 O.sub.3.
A two phase ceramic composite comprising:
- a first phase occupying 5 to 95% of the volume of said ceramic composite, said first phase comprising ZrO.sub.2 grains having a diameter less than about 2 .mu.m with a rare earth oxide dissolved therein, at least 80% of said ZrO.sub.2 having a tetragonal structure, said rare earth oxide being selected from the group consisting of Y.sub.2 O.sub.2, CeO.sub.2, and Er.sub.2 O.sub.3 ;
- and
- a second phase comprising Al.sub.2 O.sub.3 and occupying substantially all remaining volume of said ceramic composite.
A ceramic comprising:
- 5 to 95 v/o ZrO.sub.2 in the form of grains having a diameter less than about 2 .mu.m and a substantially tetragonal structure;
- 0.5 to 5 m/o La.sub.2 O.sub.3 ;
- and
- 95 to 5 v/o Al.sub.2 O.sub.3.
Dependencies are inferred from the claim text.