# US 2006/0138715 A1 · Doped ceramic materials and methods of forming the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2006/0138715 A1 - Document ID: US20060138715A1 - Status: Published application - Kind: A1 - Application number: 11/291,271 - Filed: 2005-12-01 - Published: 2006-06-29 - Earliest claimed: 2004-12-01 - Inventors: Leong Lim; Ping Liu - Web page: https://patentgrep.com/patent/US20060138715A1 ## CPC - C04B 35/64: Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F}) - C04B 41/009: {characterised by the material treated} - C04B 41/5033: {Chromium oxide} - C04B 41/87: Ceramics - B23B 2226/18: Ceramic - C04B 2111/00405: {Materials with a gradually increasing or decreasing concentration of ingredients or property from one layer to another} - C04B 2235/3241: Chromium oxides, chromates, or oxide-forming salts thereof - C04B 2235/5445: submicron sized, i.e. from 0,1 to 1 micron - C04B 2235/6027: Slip casting - C04B 2235/6581: Total pressure below 1 atmosphere, e.g. vacuum - C04B 2235/661: Multi-step sintering - C04B 2235/75: Products with a concentration gradient - C04B 2235/77: Density - C04B 2235/785: Submicron sized grains, i.e. from 0,1 to 1 micron - C04B 2235/786: Micrometer sized grains, i.e. from 1 to 100 micron - C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE - B23B: TURNING; BORING (arrangements for copying or controlling B23Q) ## Abstract A doped ceramic material comprising: a first layer comprising ceramic material and an amount of dopant, a second layer comprising the ceramic material, and a transitional layer connecting the first layer and the second layer. The transitional layer comprises the dopant in an amount which decreases in a direction from the first layer to the second layer. A method of forming the doped ceramic material is also disclosed. ## Claims ### Claim 1 A doped ceramic material comprising: (a) a first layer comprising ceramic material and an amount of dopant, (b) a second layer comprising the ceramic material, and (c) a transitional layer connecting the first layer and the second layer, said transitional layer comprising the dopant in an amount which decreases in a direction from the first layer to the second layer. ### Claim 2 (depends on 1) A doped ceramic material according to claim 1, wherein the ceramic material is formed from at least two elements selected from the group consisting of: Group IIIA elements, Group IVA elements, Group IVB elements, Group VA elements and Group VIA elements of the periodic table of elements. ### Claim 3 (depends on 2) A doped ceramic material according to claim 2, wherein the ceramic material is selected from the group consisting of SiC, Si3N4, Al2O3, AlN, ZrO2, SiO2 and composites thereof. ### Claim 4 (depends on 3) A doped ceramic material according to claim 3, wherein the ceramic material is Al2O3. ### Claim 5 (depends on 1) A doped ceramic material according to claim 1, wherein the dopant is a metal oxide. ### Claim 6 (depends on 5) A doped ceramic material according to claim 5, wherein the metal oxide is a transition metal oxide. ### Claim 7 (depends on 6) A doped ceramic material according to claim 6, wherein the transition metal oxide is chromium oxide (Cr2O3). ### Claim 8 (depends on 1) A doped ceramic material according to claim 1, wherein the amount of dopant in the first layer is selected from the group consisting of: about 0.1 mol % to about 5 mol %; about 0.3 mol % to about 5 mol %; about 0.6 mol % to about 5 mol %; about 1 mol % to about 5 mol %; about 2 mol % to about 5 mol %; about 3 mol % to about 5 mol %; about 4 mol % to about 5 mol %; about 0.1 mol % to about 4 mol %; about 0.1 mol % to about 3 mol %; about 0.1 mol % to about 2 mol %; about 0.1 mol % to about 1 mol %; about 0.1 mol % to about 0.6 mol %; and about 0.1 mol % to about 0.3 mol %. ### Claim 9 (depends on 1) A doped ceramic material according to claim 1, wherein the second layer has substantially no dopant. ### Claim 10 (depends on 1) A doped ceramic material according to claim 1, wherein the doped ceramic material has a sintered relative density of at least about 97%. ### Claim 11 (depends on 1) A doped ceramic material according to claim 1, wherein the doped ceramic material has an average grain size selected from the group consisting of: about 0.5 μm to about 5 μm; about 0.5 μm to about 4 μm; about 0.5 μm to about 3 μm; about 0.5 μm to about 2 μm; about 0.5 μm to about 1 μm; about 1 μm to about 5 μm; about 2 μm to about 5 μm; about 3 μm to about 5 μm; and about 4 μm to about 5 μm. ### Claim 12 (depends on 1) A doped ceramic material according to claim 1, wherein the doped ceramic material has a surface hardness of at least about 17 GPa. ### Claim 13 (depends on 1) A doped ceramic material according to claim 1, wherein the doped ceramic material has a fracture toughness of at least about 3.6 MPa(m1/2). ### Claim 14 A method of forming a doped ceramic material comprising the steps of: (a) providing a high sinterability ceramic preform having a first layer, a second layer and a transitional layer connecting the first layer and the second layer; (b) doping the first layer of the ceramic preform with an amount of dopant to thereby cause the amount of dopant in said transitional layer to decrease in a direction from the first layer to the second; and (c) sintering the ceramic preform at a temperature for a period of time to form the doped ceramic material. ### Claim 15 (depends on 14) A method of forming a doped ceramic material according to claim 14, wherein the first layer, the second layer and the transitional layer form an integral structure. ### Claim 16 (depends on 14) A method of forming a doped ceramic material according to claim 14, wherein the providing step (a) comprises the steps of: (a1) casting a suspension of ceramic powder into a mould to form a green body; (a2) pre-firing the green body at a temperature for a period of time to form the high sinterability ceramic preform. ### Claim 17 (depends on 16) A method of forming a doped ceramic material according to claim 16, wherein the casting step (al) comprises the step of: (a3) selecting an average particle size of the ceramic powder from the group consisting of: about 0.05 μm to about 1 μm; about 0.05 μm to about 0.8 μm; about 0.05 μm to about 0.6 μm; about 0.05 μm to about 0.4 μm; about 0.05 μm to about 0.2 μm; about 0.05 μm to about 0.1 μm; about 0.1 μm to about 1 μm; about 0.2 μm to about 1 μm; about 0.4 μm to about 1 μm; about 0.6 μm to about 1 μm; about 0.8 μm to about 1 μm; and about 0.1 μm to about 0.2 μm. ### Claim 18 (depends on 16) A method of forming a doped ceramic material according to claim 16, wherein the pre-firing step (a2) comprises the step of: (a4) pre-firing the green body at a temperature selected from the group consisting of: about 700° C. to about 1100° C.; about 800° C. to about 1100° C.; about 9000° C. to about 1100° C.; about 1000° C. to about 1100° C.; about 700° C. to about 1000° C.; about 700° C. to about 900° C.; and about 700° C. to about 800° C. ### Claim 19 (depends on 16) A method of forming a doped ceramic material according to claim 16, wherein the pre-firing step (a2) comprises the step of: (a5) pre-firing the green body for a time period selected from the group consisting of: about 1 hour to about 4 hours; about 2 hours to about 4 hours; about 3 hours to about 4 hours; about 1 hour to about 3 hours; and about 1 hour to about 2 hours. ### Claim 20 (depends on 14) A method of forming doped ceramic material according to claim 14, wherein the providing step (a) comprises the step of: (a6) selecting the ceramic preform from compounds formed from at least two elements selected from the group consisting of: Group IIIA elements, Group IVA elements, Group IVB elements, Group VA elements and Group VIA elements of the periodic table of elements. ### Claim 21 (depends on 20) A method of forming a doped ceramic material according to claim 20, wherein the selecting step (a6) comprises the step of: (a7) selecting the ceramic preform from the group consisting of SiC, Si3N4, Al2O3, AlN, ZrO2, SiO2 and composites thereof. ### Claim 22 (depends on 14) A method of forming a doped ceramic material according to claim 14, wherein the providing step (a) comprises the steps of: (a8) shaping the ceramic preform. ### Claim 23 (depends on 21) A method of forming a doped ceramic material according to claim 21, wherein the selecting step (a7) comprises the step of: (a7) selecting Al2O3 as the ceramic preform. ### Claim 24 (depends on 14) A method of forming a doped ceramic material according to claim 14, wherein the doping step (b) comprises the step of: (b1) selecting a metal oxide as the dopant. ### Claim 25 (depends on 24) A method of forming a doped ceramic material according to claim 24, wherein the selecting step (b1) comprises the step of: (b2) selecting a transition metal oxide as the metal oxide. ### Claim 26 (depends on 25) A method of forming a doped ceramic material according to claim 25, wherein the selecting step (b2) comprises the step of: (b3) selecting chromium oxide (Cr2O3) as the transition metal oxide. ### Claim 27 (depends on 14) A method of forming a doped ceramic material according to claim 14, wherein the doping step (b) comprises the step of: (b4) selecting the amount of dopant in the first layer from the group consisting of: about 0.1 mol % to about 5 mol %; about 0.3 mol % to about 5 mol %; about 0.6 mol % to about 5 mol %; about 1 mol % to about 5 mol %; about 2 mol % to about 5 mol %; about 3 mol % to about 5 mol %; about 4 mol % to about 5 mol %; about 0.1 mol % to about 4 mol %; about 0.1 mol % to about 3 mol %; about 0.1 mol % to about 2 mol %; about 0.1 mol % to about 1 mol %; about 0.1 mol % to about 0.6 mol %; and about 0.1 mol % to about 0.3 mol %. ### Claim 28 (depends on 14) A method of forming a doped ceramic material according to claim 14, wherein the doping step (b) comprises the step of: (b5) selecting the amount of dopant in the second layer as about 0 mol %. ### Claim 29 (depends on 14) A method of forming a ceramic material according to claim 14, wherein the doping step (b) comprises the step of: (b6) immersing the ceramic preform into a solution having a selected concentration of the dopant for a selected period of time to dope the first layer with the selected amount of dopant and to cause infiltration of the dopant into the ceramic preform. ### Claim 30 (depends on 29) A method of forming a ceramic material according to claim 29, wherein the immersing step (b6) comprises the step of: (b7) immersing the ceramic preform into a solution of dopant for a period of time selected from the group consisting of: about 15 minutes to about 5 hours; about 30 minutes to about 5 hours; about 1 hour to about 5 hours; about 2 hours to about 5 hours; about 3 hours to about 5 hours; about 4 hours to about 5 hours; about 15 minutes to about 4 hours; about 15 minutes to about 3 hours; about 15 minutes to about 2 hours; about 15 minutes to about 1 hour; and about 15 minutes to about 30 minutes. ### Claim 31 (depends on 29) A method of forming a ceramic material according to claim 29, wherein the immersing step (b6) comprises the step of: (b8) immersing the ceramic preform in a saturated solution of the dopant. ### Claim 32 (depends on 14) A method of forming a ceramic material according to claim 14, wherein said sintering step (c) comprises the step of: (c1) sintering the ceramic preform at a temperature selected from the group consisting of: about 1200° C. to about 1600° C.; about 1200° C. to about 1500° C.; about 1200° C. to about 1400° C.; about 1200° C. to about 1300° C.; about 1300° C. to about 1600° C.; about 1400° C. to about 1600° C.; about 1500° C. to about 1600° C.; and about 1350° C. to about 1550° C. ### Claim 33 (depends on 14) A method of forming a ceramic material according to claim 14, wherein the sintering step (c) comprises the step of: (c2) sintering the ceramic preform for a period of time selected from the group consisting of: about 1 hour to about 24 hours; about 5 hours to about 24 hours; about 10 hours to about 24 hours; about 15 hours to about 24 hours; about 20 hours to about 24 hours; about 1 hour to about 20 hours; about 1 hour to about 15 hours; about 1 hour to about 10 hours; and about 1 hour to about 5 hours. ### Claim 34 (depends on 14) A method of forming a ceramic material according to claim 14, wherein the sintering step (c) comprises the step of: (c3) sintering the ceramic preform in a vacuum. ### Claim 35 (depends on 14) A method of forming a ceramic material according to claim 14, wherein the sintering step (c) comprises the step of: (c4) sintering the ceramic preform in an environment of gases selected from the group consisting of: oxygen gas, nitrogen gas, argon gas, air and combinations thereof. ### Claim 36 A chromium oxide (Cr2O3) doped alumina (Al2O3) material comprising: (a) a first layer comprising Al2O3 and an amount of Cr2O3, (b) a second layer comprising Al2O3, and (c) a transitional layer connecting the first layer and the second layer, said transitional layer comprising Cr2O3 in an amount which decreases in a direction from the first layer to the second layer. ### Claim 37 A method of forming Chromium Oxide (Cr2O3) doped alumina (Al2O3) material comprising the steps of: (a) providing a high sinterability Al2O3 preform having a first layer, a second layer and a transitional layer connecting the first layer and the second layer; (b) doping the first layer with an amount of Cr2O3 to thereby cause the amount of Cr2O3 in said transitional layer to decrease in a direction from the first layer to the second; and (c) sintering the Al2O3 preform at a temperature for a period of time to form the Cr2O3 doped Al2O3 material.