Nec Corporation

Hitachi Metals Precision, Ltd.

Katsuhisa Ishikawa

Yasuhiro Sasaki

Atsushi Ochi

Yoshitsugu Okada

Osamu Myohga

Mitsuru Furuya

Ryoji Yamamoto

Takayuki Tsukahara

A Ni--Zn type ferrite has the composition represented by the general formula: Ni.sub.X Zn.sub.1-X Fe.sub.2-Y-Z Mn.sub.Y Zr.sub.Z O.sub.4 (0.55.ltoreq.X.ltoreq.0.80, 0.001.ltoreq.Y.ltoreq.0.20, 0.001.ltoreq.Z.ltoreq.0.04). The Ni--Zn type ferrite is formed with the step described below. A raw powder is first mixed for 64 hours and then fired at 850.degree. C. in an oxygen atmosphere for two hours. Next, the fired powder is crushed and then the crushed powder is again mixed. Then, a binder is added to the resulting powder, which is then press-formed under a pressure of 2.5 ton/cm.sup.2, and the press-formed powder is sintered at 1350.degree. C. for 5 hours in an oxygen atmosphere.

Ni-Zn type ferrite

A Ni--Zn base ferrite is provided with a relatively small dielectric loss (tan.delta.(.epsilon.)) of the order of 10.sup.-3. Its saturation magnetization (4.pi.Ms) is relatively still high. A Ni--Zn base ferrite having a small dielectric loss (of the order of 10.sup.-3) can be obtained by proportioning raw materials to give a finished composition range of Ni.sub.X Zn.sub.1-X Fe.sub.2-Y-Z Mn.sub.Y M.sub.Z O.sub.4 where M: Ge and/or Sn, 0.55.ltoreq.X.ltoreq.1.00, 0.001.ltoreq.Y.ltoreq.0.36, and 0.002.ltoreq.Z.ltoreq.0.36, by calcination.

Ni-Zn base ferrite

A novel low thermal expansion cast alloy is provided. The alloy consists of, by percents by weight, 0.02 to 0.25% of C, 30.5 to 33.3% of Ni, 4.0 to 6.0% of Co, 0.005 to 0.70% of Mn, 0.005-0.50% of Si and the balance substantially of Fe, with the proviso that % C.gtoreq.3.0285-0.0936 x % Ni (% C and % Ni are weight % of C and Ni). By such composition, micro-segregation of Ni can be reduced and the Ni content range showing the low thermal expansion coefficient can be broadened to an extent of substantially enabling mass production by a casting process in place of the conventional forging or rolling process. The average thermal expansion coefficient at the temperature range from - 50 to 120.degree. C. of the cast alloy is not more than 1.5.times.10.sup.-6 /.degree.C.

Low thermal expansion cast alloy

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Tokyo, Japan

Katsuhisa Ishikawa