Tdk Corporation

Yoshito Nihira

Takeshi Nomura

Masahiro Onizuka

Hisanao Tosaka

Noriaki Hirano

Haoren Zhuang

A PTC thermistorcomprises, at least, a pair of electrodesand a thermistor body, disposed between the electrodes, having a positive resistance vs. temperature characteristic. The thermistor body includes, at least, a thermoplastic resin and an electrically conductive particle made of a metal powder. The thermoplastic resin and electrically conductive particle have respective contents and a state of dispersion adjusted so as to yield a magnetization of 4.0&#xd7;10to 6.0&#xd7;10Wb&#xb7;m&#xb7;kgwhen a magnetic field of 3.98&#xd7;10A&#xb7;mis applied to the thermistor body.

PTC thermistor body, PTC thermistor, method of making PTC thermistor body, and method of making PTC thermistor

Ferrite materials including spinel and magnetoplumbite ferrite materials are prepared by using a mixture containing at least one metal chloride and at least one metal oxide as a starting raw material and roasting the mixture in a steam-containing atmosphere to carry out pyrolysis reaction and solid phase reaction at the same time.

Preparation of ferrite materials

Ferrous chloride is used as a starting material and roasted in a steam-containing atmosphere for pyrolysis to prepare a magnetite magnetic powder having a saturation magnetization .sigma.s of 82-92 emu/g and a magnetite phase content of at least 90 wt. %. Prior to roasting, the ferrous chloride may be pre-treated by heat treating it at a low temperature in a non-oxidizing atmosphere, cooling it down to a predetermined temperature, and then exposing it to an oxygen-containing atmosphere. A mixture of ferrous chloride and ferric chloride may also be used as the starting material. These methods can produce magnetite magnetic powder having improved magnetic properties through fewer steps in a simple and easy manner.

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Chiba, Japan

Yoshito Nihira