METHOD OF MAKING A POLYCRYSTALLINE MN CONTAINING FERRITE BODY

摘要

1436015 Manganese ferrite MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 11 Dec 1973 [11 Dec 1972] 57425/73 Headings C1A and C1J A polycrystalline manganese ferrite material comprising crystallites of which a substantial proportion are disposed in substantially parallel crystallographic planes (claimed per se) is made by providing a manganese compound in the form of platelets and ferrite constituents, orienting these and sintering. The manganese compound which may be formed into a body with ferrite constituents, may beγ-MnOOH, #-MnO 2 ,α- MnOOH,γ-MnO 2 , #-MnOOH, #-MnOOH or Mn(OH) 2 or products of these by pyrolysis at below 900‹ C. The orientation may be done by precipitating the manganese compound in a liquid and/or cold pressing at 500-3000 kg./cm.2 The manganese compound and ferrite constituent may be mixed before or after orienting. The sintering may be done at above 1000‹ C. and in a vacuum or an inert gas. The body may be hot-pressed. The degree of orientation may be over 50%. The initial platelets may have a grain size greater than 0À01 Á and the product a grain size greater than 10 Á. The ferrite constituents may include Co, Zn, Ni, Mg, Li and Cu. The product may be used in the magnetic heads of audio- and video-tape-recorders.