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EP0250153A2
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Silicon nitride sintered bodies and process for manufacturing the same
Assignee: NGK Insulators Ltd
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Filing: 1987-06-10
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Granted: —
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Expires: 2007-06-10
Abstract
Abstract Silicon nitride sintered bodies of high strength at high temperature comprise not less than 70% by weight of Si₃N₄ and essentially consist of Si, O, N and a remainder being at least two of the rare earth elements Y, Er, Tm, Yb and Lu. The ratio of the molar amount of all the rare earth elements when calculated as Ln₂O₃ in which Ln is Y, Er, Tm, Yb or Lu to the molar amount of oxygen when calculated as SiO₂ is in a range from 0.4 to 1.3. The amount of oxygen when calculated as SiO₂ is obtained by subtracting the amount of oxygen in all the Ln₂O₃ from the amount of oxygen in the sintered body and expressing the remaining amount of oxygen as SiO₂ . Each of the rare earth elements is not more than 95 mol% of the sum of all the rare earth elements in the sintered body. The intergranular phase of the Si₃N₄ grains is substantially a crystalline phase of which not less than 50% is a crystalline phase of an apatite structure. Such bodies can be made by pressureless sintering or sintering in a pressurized atmosphere.
Inventors
- 👤 Takao Soma
- 👤 Tomonori Takahashi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 22:53
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/5935
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
201 words
A silicon nitride sintered body comprising not less than 70% by weight of Si₃N₄ and essentially consisting of Si, O, N and a remainder being at least two rare earth elements selected from Y, Er, Tm, Yb and Lu, wherein (1) the ratio of the molar amount of all the rare earth elements in said sintered body when calculated as Ln₂O₃ in which Ln is Y, Er, Tm, Yb or Lu with respect to the molar amount of oxygen when calculated as SiO₂ is in the range from 0.4 to 1.3, said amount of oxygen when calculated as SiO₂ being obtained by subtracting the amount of oxygen in Ln₂O₃ obtained by expressing all the rare earth elements present as Ln₂O₃ from the amount of oxygen in said sintered body and converting the remaining amount of oxygen into Si02 (2) any one of the rare earth elements in said sintered body is not more than 95 mol% of the sum of all the rare earth elements in the sintered body and (3) the intergranular phase of the Si₃N₄ grains in said sintered body is substantially a crystalline phase of which not less than 50% is a crystalline phase of an apatite structure.
Claim 2
Dependent Claim
201 words
A silicon nitride sintered body comprising not less than 70% by weight of Si₃N₄ and essentially consisting of Si, O, N and a remainder being at least two rare earth elements selected from Y, Er, Tm, Yb and Lu, wherein (1) the ratio of the molar amount of all the rare earth elements in said sintered body when calculated as Ln₂O₃ in which Ln is Y, Er, Tm, Yb or Lu with respect to the molar amount of oxygen when calculated as SiO₂ is in the range from 0.4 to 1.3, said amount of oxygen when calculated as SiO₂ being obtained by subtracting the amount of oxygen in Ln₂O₃ obtained by expressing all the rare earth elements present as Ln₂O₃ from the amount of oxygen in said sintered body and converting the remaining amount of oxygen into Si02 (2) any one of the rare earth elements in said sintered body is not more than 95 mol% of the sum of all the rare earth elements in the sintered body and (3) the intergranular phase of the Si₃N₄ grains in said sintered body is substantially a crystalline phase of which not less than 50% is a crystalline phase of an apatite structure.
Claim 3
Dependent Claim
27 words
A silicon nitride sintered body according to claim 1, wherein Yb is present in an amount of 50 to 95 mol% of all the rare earth elements.
Claim 4
Dependent Claim
18 words
A silicon nitride sintered body according to claim 2, wherein the rare earth elements comprise Y and Yb.
Claim 5
Dependent Claim
161 words
A process for manufacturing a silicon nitride sintered body, which comprises preparing a mixed powder consisting of a raw material powder of silicon nitride and two or more rare earth element oxides selected from Y₂O₃, Er₂O₃, Tm₂O₃, Yb₂O₃ and Lu₂O₃ (or compounds convertible into two or more of those oxides), molding said mixed powder, and then firing a thus obtained molding at 1,700°C to 2,100°C pressurelessly or in a pressurized N₂ atmosphere, wherein any one of said selected rare earth element oxides is not more than 95 mol% of the total addition amount of the oxides of the rare earth elements and the ratio of the total addition molar amount of the selected oxides of the rare earth elements to the molar amount of SiO₂ which is obtained by calculating all oxygen contained in said sintered body (excluding oxygen introduced into the sintered body from the added rare earth element oxides) as SiO₂ is in a range from 0.4 to 1.3.
Claim 6
Dependent Claim
161 words
A process for manufacturing a silicon nitride sintered body, which comprises preparing a mixed powder consisting of a raw material powder of silicon nitride and two or more rare earth element oxides selected from Y₂O₃, Er₂O₃, Tm₂O₃, Yb₂O₃ and Lu₂O₃ (or compounds convertible into two or more of those oxides), molding said mixed powder, and then firing a thus obtained molding at 1,700°C to 2,100°C pressurelessly or in a pressurized N₂ atmosphere, wherein any one of said selected rare earth element oxides is not more than 95 mol% of the total addition amount of the oxides of the rare earth elements and the ratio of the total addition molar amount of the selected oxides of the rare earth elements to the molar amount of SiO₂ which is obtained by calculating all oxygen contained in said sintered body (excluding oxygen introduced into the sintered body from the added rare earth element oxides) as SiO₂ is in a range from 0.4 to 1.3.
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