Hitachi Metals, Ltd.

Masahisa Sobue

Tsunehiro Kawata

Hisayuki Imamura

Shigeyuki Hamayoshi

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&#x2013;7 weight %, with Mg converted to MgO and rare earth elements converted to rare earth oxides REO. The silicon nitride sintered body is produced by mixing 1&#x2013;50 parts by weight of a first silicon nitride powder having a &#x3b2;-particle ratio of 30&#x2013;100%, an oxygen content of 0.5 weight % or less, an average particle size of 0.2&#x2013;10 &#x3bc;m, and an aspect ratio of 10 or less, with 99&#x2013;50 parts by weight of &#x3b1;-silicon nitride powder having an average particle size of 0.2&#x2013;4 &#x3bc;m; and sintering the resultant mixture at a temperature of 1,800&#xb0; C. or higher and pressure of 5 atm or more in a nitrogen atmosphere.

Silicon nitride powder, silicon nitride sintered body, sintered silicon nitride substrate, and circuit board and thermoelectric module comprising such sintered silicon nitride substrate

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 REO. 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 &#x3bc;m, and an aspect ratio of 10 or less, with 99&#x2212;50 parts by weight of &#x3b1;-silicon nitride powder having an average particle size of 0.2-4 &#x3bc;m; and sintering the resultant mixture at a temperature of 1,800&#xb0; C. or higher and pressure of 5 atm or more in a nitrogen atmosphere.

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Saitama-ken, Japan

Masahisa Sobue