| 摘要 |
An Si3N4 sintered body produced by reactive sintering of silicon, wherein a compound of at least one element selected from the group consisting of Y, Yb and Sm is contained by 0.6 to 13% by weight as Ln2O3 (wherein Ln=Y, Yb or Sm), an oxygen content in Si3N4 crystal grains is not more than 1% by weight, a ratio of Si and Ln in the Si3N4 sintered body is within a range of 0.1 to 0.8 in a molar ratio of SiO2/Ln2O3 of the Si in terms of SiO2 to the oxide Ln2O3, and the sintered body has a relative density of 85 to 99.9%, a thermal conductivity of at least 70 W/m.K or more and a three-point bending strength of at least 600 MPa. The Si3N4 sintered body is produced by mixing 80 to 99% by weight of silicon powder and 1 to 20% by weight of powder of oxide of at least one element of Y, Yb and SM, by nitriding a molded body of the powder mixture in an atmosphere containing nitrogen at 1400° C. or less, and then sintering the nitrided body in an atmosphere containing nitrogen at a temperature of 1700 to 1950° C. In the production, a coupling agent including C, H, O and metal cations (e.g., Si or Ti) can be used as a reducing coating agent to further improve the thermal conductivity.
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