Study on a Method to Control the Oxygen Content in the Sintering Atmosphere for MnZn Ferrites

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  • Isaka Akira
    The Electrical Communication, Laboratory, Nippon Telegraph and Telephone Public Corporation
  • Matsumoto Yasushi
    The Electrical Communication, Laboratory, Nippon Telegraph and Telephone Public Corporation
  • Sugihara Makoto
    The Electrical Communication, Laboratory, Nippon Telegraph and Telephone Public Corporation

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  • MnZnフェライトの焼成雰囲気制御法に関する研究
  • MnZn フェライト ノ ショウセイ フンイキ セイギョホウ ニ カンスル ケンキュウ

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Abstract

An appropriate method to control the oxygen content in the sintering atmosphere for MnZn ferrites was devised to obtain high quality magnetic cores of the ferrites. The magnetic properties of MnZn ferrites are influenced particularly by the sintering atomosphere. In order to obtain low loss ferrites, it requires to choose a proper oxygen content in the ambient sintering atomosphere. Since the ferrites are ionic crystals, an equation of Clausius-Clapeylon can be applied to the relation between vaper pressure and temperature. In this case, the logarithm of oxygen pressure has a liner relation to the inverse of absolute temperature. Therefore, a method to control the equilibrium atomosphere successively for sintering and cooling temperatures has been investigated to satisfy this relation. When the inert gas flows with a constant velocity into the closed furnace filled up with a mixture gas of oxygen and nitrogen in a proper proportion, the oxygen content is reduced exponentially. It was found experimently that the oxygen per cent Pt at the time t is expressed by the formula Pt=P0exp(−At⁄αV). The relation could be applied to obtain any desirable equilibrium atomosphere at the temperatures during the sintering and cooling processes. The magnetic properties of the ferrites prepared by this method were measured, with the result that these ferrites have high permeability, low loss and a homogeneous structure.

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