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AssigneeHitachi Metals, Ltd.
InventorsHisayuki Imamura, Shigeyuki Hamayoshi, Tsunehiro Kawata, Masahisa Sobue
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A silicon nitride sintered body comprising Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, the total oxide-converted content of the above elements being 0.6-7 weight %, with Mg converted to MgO and rare earth elements converted to rare earth oxides RExOy. The silicon nitride sintered body is produced by mixing 1-50 parts by weight of a first silicon nitride powder having a particle ratio of 30-100%, an oxygen content of 0.5 weight % or less, an average particle size of 0.2-10 μm, and an aspect ratio of 10 or less, with 99−50 parts by weight of α-silicon nitride powder having an average particle size of 0.2-4 μm; and sintering the resultant mixture at a temperature of 1,800° C. or higher and pressure of 5 atm or more in a nitrogen atmosphere.
A silicon nitride sintered body comprising Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, the total oxide-converted content of said Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb being 0.6-7 weight %, with Mg converted to MgO and rare earth elements converted to rare earth oxides y in which nano-size, fine particles at least containing Mg, at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, and O and having an average particle size of 100 nm or less are observed in silicon nitride grains, in a transmission electron micrograph having a magnitude of 10,000 times or more.
A silicon nitride substrate constituted by a silicon nitride sintered body comprising Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, the total oxide-converted content of said elements Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb being 0.6-7 weight %, with Mg converted to MgO and rare earth elements converted to rare earth oxides RExOy, and a weight ratio expressed by MgO/RExOy of 3-70, wherein said substrate has a surface texture having a centerline average surface roughness Ra of 0.2-20 μM and consists essentially of silicon nitride grains and grain boundaries, an area ratio of said silicon nitride grains being 70-100% in a substrate surface, assuming that the total area ratio of said silicon nitride grains and said grain boundaries is 100%.
A silicon nitride substrate constituted by a silicon nitride sintered body comprising Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, the total oxide-converted content of said Mg and at least one rare earth element selected from the group consisting of La, Y, Gd and Yb being 0.6-7 weight %, with Mg converted to MgO and rare earth elements converted to rare earth oxides RExOy, in which nano-size, fine particles at least containing Mg, at least one rare earth element selected from the group consisting of La, Y, Gd and Yb, and O and having an average particle size of 100 nm or less are observed in silicon nitride grains, in a transmission electron micrograph having a magnitude of 10,000 times or more,
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