Zirconia ceramics and process for producing the same

Claim 2

A ceramic comprising a sintered body containing zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, the proportions of zirconium oxide and cerium oxide being 74 to 84% by weight of zirconium oxide and 26 to 16% by weight of cerium oxide, and the proportions of zirconium oxide-cerium oxide and aluminum ozide being 99.9 to 80% by weight of zirconium oxide-cerium oxide and 0.1 to 20% by weight of aluminum oxide.

Claim 3

A ceramic according to claim 1, wherein the proportions of zirconium oxide-cerium oxide-cerium and aluminum oxide is 95 to 99.9% by weight of zirconium oxide-cerium oxide and and 0.1 to 5% by weight of aluminum oxide.

Claim 4

A ceramic according to claim 1, wherein the proportions of zirconium oxide and cerium oxide is 79 to 84% by weight of zirconium oxide and 16 to 21% by weight of cerium oxide.,

Claim 5

A process for producing a ceramic comprising a sintered body containing zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, which comprises: heat treating a mixture of 74 to 84% by weight of zirconium oxide powder and 16 to 26% by weight of cerium oxide powder at a temperature of 1000° to 1500° C. to give an intermediate oxide mixture, adding 0.1 to 20% by weight of aluminum compound in terms of the weight of aluminum oxide to 80 to 99.9% by weight of the intermediate oxide mixture, mixing, grinding and molding the resulting mixture, and sintering the molded mixture at a temperature of 1500° to 1700° C. to form said sintered body.

Claim 6

A process for producing a ceramic comprising a sintered body containing zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, which comprises: heat treating a mixture of 74 to 84% by weight of zirconium oxide powder and 16 to 26% by weight of cerium oxide powder at a temperature of 1000° to 1500° C. to give an intermediate oxide mixture, adding 0.1 to 20% by weight of aluminum compound in terms of the weight of aluminum oxide to 80 to 99.9% by weight of the intermediate oxide mixture, mixing, grinding and molding the resulting mixture, and sintering the molded mixture at a temperature of 1500° to 1700° C. to form said sintered body.

Claim 7

A process according to claim 4, wherein 0.1 to 5% by weight of aluminum compound in terms of the weight of aluminum oxide is added to 95 to 99.9% by weight of the intermediate mixture.

Claim 8

A process according to claim 4, wherein the intermediate mixture comprises 79 to 84% by weight of zirconium oxide and 16 to 21% by weight of cerium oxide.

Claim 9

A ceramic comprising a sintered body consisting essentially of zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals; said sintered body being produced by heat treating a mixture consisting essentially of 74% to 84% by weight of zirconium oxide and 26 to 16% by weight of cerium oxide at a temperature of 1000° to 1500° C. to give an intermediate oxide mixture, by adding 0.1 to 20% by weight of at least one aluminum compound in terms of the weight of aluminum oxide to 80 to 99.9% by weight of the intermediate mixture, thereafter by mixing, grinding and molding the resulting mixture, and by sintering the molded mixture at a temperature of 1500° to 1700° C.

Claim 10

A ceramic comprising a sintered body consisting essentially of zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals; said sintered body being produced by heat treating a mixture consisting essentially of 74% to 84% by weight of zirconium oxide and 26 to 16% by weight of cerium oxide at a temperature of 1000° to 1500° C. to give an intermediate oxide mixture, by adding 0.1 to 20% by weight of at least one aluminum compound in terms of the weight of aluminum oxide to 80 to 99.9% by weight of the intermediate mixture, thereafter by mixing, grinding and molding the resulting mixture, and by sintering the molded mixture at a temperature of 1500° to 1700° C.

Claim 11

A ceramic according to claim 7, wherein 0.1 to 5% by weight of aluminum oxide is added to 95 to 99.9% by weight of the intermediate mixture.

Claim 12

A ceramic according to claim 7, wherein the heat-treated mixture consists essentially of 79 to 84% by weight of zirconium oxide and 16 to 21% by weight of cerium oxide.

Claim 13

A ceramic according to claim 7, wherein said sintered body includes up to 2% by weight of SiO 2 , TiO 2 and Fe 2 O 3 as impurities.

Claim 14

A process for producing a ceramic comprising a sintered body consisting essentially of zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, which comprises: heat treating a mixture consisting essentially of 74 to 84% by weight of zirconium oxide powder and 16 to 26% by weight of cerium oxide powder at a temperature of 1000° to 1500° C. to give an intermediate oxide mixture, adding 0.1 to 20% by weight of an aluminum compound in terms of the weight of aluminum oxide to 80 to 99.9% by weight of the intermediate oxide mixture, mixing, grinding and molding the resulting mixture, and sintering the molded mixture at a temperature of 1500° to 1700° C. to form said sintered body.

Claim 15

A process for producing a ceramic comprising a sintered body consisting essentially of zirconium oxide, cerium oxide and aluminum oxide in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, which comprises: heat treating a mixture consisting essentially of 74 to 84% by weight of zirconium oxide powder and 16 to 26% by weight of cerium oxide powder at a temperature of 1000° to 1500° C. to give an intermediate oxide mixture, adding 0.1 to 20% by weight of an aluminum compound in terms of the weight of aluminum oxide to 80 to 99.9% by weight of the intermediate oxide mixture, mixing, grinding and molding the resulting mixture, and sintering the molded mixture at a temperature of 1500° to 1700° C. to form said sintered body.

Claim 16

A process according to claim 11, wherein 0.1 to 5% by weight of the aluminum compound in terms of the weight of aluminum oxide is added to 95 to 99.9% by weight of the intermediate oxide mixture.

Claim 17

A process according to claim 11, wherein the intermediate oxide mixture consists essentially of 79 to 84% by weight of zirconium oxide and 16 to 21% by weight of cerium oxide.

Claim 18

A ceramic comprising a sintered body consisting of zirconium oxide, cerium oxide, aluminum oxide and impurities in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, the proportions of zirconium oxide and cerium oxide being 74 to 84% by weight of zirconium oxide and 26 to 16% by weight of cerium oxide, the proportions of zirconium oxide-cerium oxide and aluminum oxide being 99.9 to 80% by weight of zirconium oxide-cerium oxide and 0.1 to 20% by weight of aluminum oxide; and the proportions of impurities being up to 2% by weight of SiO 2 , TiO 2 and Fe 2 O 3 based on the weight of the sintered body.

Claim 19

A ceramic comprising a sintered body consisting of zirconium oxide, cerium oxide, aluminum oxide and impurities in the form of tetragonal crystals with 20% by weight or less of monoclinic and/or cubic crystals, the proportions of zirconium oxide and cerium oxide being 74 to 84% by weight of zirconium oxide and 26 to 16% by weight of cerium oxide, the proportions of zirconium oxide-cerium oxide and aluminum oxide being 99.9 to 80% by weight of zirconium oxide-cerium oxide and 0.1 to 20% by weight of aluminum oxide; and the proportions of impurities being up to 2% by weight of SiO 2 , TiO 2 and Fe 2 O 3 based on the weight of the sintered body.

Claim 20

A ceramic according to claim 7, wherein the heat-treated mixture consists of 79 to 84% by weight of zirconium oxide and 16 to 21% by weight of cerium oxide.

Claim 21

A process according to claim 11, wherein the intermediate oxide mixture consists of 79 to 84% by weight of zirconium oxide and 16 to 21% by weight of cerium oxide.

Claim 22

A process according to claim 16, wherein 0.1 to 5% by weight of the aluminum compound interms of the weight of aluminum oxide is added to 95 to 99.9% by weight of the intermediate oxide mixture.