Patent GB-822097-A (GB)
Title: Improvements in methods of manufacturing ferromagnetic ferrite bodies from ferromagnetic ferrite materials
IPC: C04B35/26
Filed: 1957-05-30
Abstract: 822,097. Magnetic compositions. PHILIPS ELECTRICAL INDUSTRIES Ltd. May 30, 1957 [June 2, 1956], No. 17206/57. Drawings to Specification. Class 38 (2). Bodies exhibiting soft magnetic properties are made by sintering or compressing the particles of a powder which have been aligned in a magnetic field, the powder being of a ferromagnetic material, the crystals of which exhibit a non- cubic crystal structure and show a preferred plane of magnetization. A method of determining whether the crystals exhibit a preferred plane of magnetization is described. Four classes of suitable material are specified, viz: (a) BaM 2 <SP>II</SP>Fe 16 <SP>III</SP>O 27 , where Ba may be wholly or partly replaced by Sr, Pb, and/or up to 40% by Ca; the Fe<SP>III</SP> may be replaced up to 20% by Al and/or Cr; and M<SP>II</SP> is one or more of Fe, Mn, Co, Ni, Zn, Mg, Li<SP>I</SP>+Fe<SP>III</SP>/2 ; (b) B 3 M 2 <SP>II</SP>Fe 24 <SP>III</SP>O 4 , where Ba may be replaced up to 1/3 by Sr, to 1/5 by Pb, to 1/10 by Ca, and where M<SP>II</SP> is one or more of Fe, Mn, Co, Cu, Ni, Zn, Mg, Li<SP>I</SP>+Fe<SP>III</SP>/2 ; (c) BaM<SP>II</SP>Fe 6 <SP>III</SP>O 11 , where Ba may be replaced up to ¢ by Sr and up to “ by Ca or Pb, where Fe<SP>III</SP> may be replaced up to <SP>1</SP>/ 10  by Al and/or Cr, and where M<SP>II</SP> is one or more of Mn, Fe, Co, Ni, Cu, Zn, Mg; (d) BaCo a <SP>II</SP>Tia<SP>IV</SP>Fe (12-2a) <SP>III</SP>O 19 , where 1.0<a<1.6, the Ba may be wholly or partly replaced by Sr, Pb and/or up to <SP>2</SP>/ 5  by Ca. An example of group (b), Ba 3 Co 2 Fe 24 O 41 , was made by grinding cobalt carbonate, barium carbonate, and ferric oxide in alcohol for 15 hours, drying it and firing in oxygen at 1050‹ C. for 2 hours; regrinding and firing at 1200‹ C. and grinding again. Test rings and rods were made from this material by compression in steady unidirectional and steady and varying rotating magnetic fields followed optionally by sintering at 1300‹ or 1290‹ C. for 2 hours in oxygen. For comparison similar samples were made without using a magnetic field. An example of group (c), BaZnFe 6 O 11 , was made by grinding zinc oxide, barium carbonate, and ferric oxide in alcohol for 15 hours and firing in oxygen at 1100‹, 1200‹ and 1260‹ C. for two hours and regrinding. Test rings and rods were made by compressing the material with or without a rotating magnetic field, and optionally sintering at 1275‹ C. in oxygen. Other examples of group (b), Ba 3 CoZnFe 24 O 41 , Ba 3 Co 0À8 Zn 1À2 Fe 24 O 41  and Ba 3 Co 2 Fe 24 O 41  were made by grinding appropriate carbonates and oxides in alcohol, drying, prefiring in oxyegn at 1250‹ or 1200‹ C. for 2 hours, and regrinding. Test rings were made by compressing the material with and without a rotating magnetic field and sintering at 1240‹ or 1200‹ C. in oxygen. The initial permeability of each specimen was measured, and the results tabulated, showing that higher values were obtained by the alignment in a magnetic field. Specification 557,838 is referred to.