Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
58 words
A silicon nitride sintered body consisting essentially of 1.5 to 3.0% by weight of yttrium oxide, 0.1 to 1.0% by weight of aluminum oxide, and 96 to 98.4% by weight of silicon nitride, wherein the yttrium oxide/aluminum oxide weight ratio is at least 2.5 and the density of the silicon nitride sintered body is at least 3.0 g/cm³.
Claim 2
Dependent Claim
58 words
A silicon nitride sintered body consisting essentially of 1.5 to 3.0% by weight of yttrium oxide, 0.1 to 1.0% by weight of aluminum oxide, and 96 to 98.4% by weight of silicon nitride, wherein the yttrium oxide/aluminum oxide weight ratio is at least 2.5 and the density of the silicon nitride sintered body is at least 3.0 g/cm³.
Claim 3
Dependent Claim
103 words
A process for the preparation of a silicon nitride sintered body, which comprises sintering a powdery silicon nitride mixture consisting essentially of 1.5 to 3.0% by weight of yttrium oxide powder, 0.1 to 1.0% by weight of aluminum oxide powder, and 96 to 98.4% by weight of silicon nitride powder, the yttrium oxide/aluminum oxide weight ratio being at least 2.5, the oxygen content in the silicon nitride powder being not more than 2.0% by weight and the total metallic impurity content in the silicon nitride powder being not more than 200 ppm, at a temperature of 1,850°C to 2,000°C in a non-oxidizing atmosphere.
Claim 4
Dependent Claim
103 words
A process for the preparation of a silicon nitride sintered body, which comprises sintering a powdery silicon nitride mixture consisting essentially of 1.5 to 3.0% by weight of yttrium oxide powder, 0.1 to 1.0% by weight of aluminum oxide powder, and 96 to 98.4% by weight of silicon nitride powder, the yttrium oxide/aluminum oxide weight ratio being at least 2.5, the oxygen content in the silicon nitride powder being not more than 2.0% by weight and the total metallic impurity content in the silicon nitride powder being not more than 200 ppm, at a temperature of 1,850°C to 2,000°C in a non-oxidizing atmosphere.
Claim 5
Dependent Claim
24 words
A process according to claim 2 wherein said sintering is effected at a temperature of about 1,850°C to 1,900°C by the pressureless sintering method.
Claim 6
Dependent Claim
22 words
A process according to claim 2 wherein said sintering is effected at a temperature of 1,900°C to 2,000°C by the gas-comprising method.