| 摘要 |
1,209,439. Ferrites; magnetic cores. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 5 June, 1969 [8 June, 1968], No. 28564/69. Heading H1H. A soft magnetic lithium-zinc-nickel ferrite material has the composition in mole per cent: Fe 2 O 3 74À5-80; Li 2 O 12À5-14À6; ZnO 3À0- 8À0; NiO up to 6À1. A sintered ferrite body, e.g. an annular core, is made by pre-firing a mixture of oxides and/or oxide-forming compounds of the above metals in the above proportions, forming a body of the pulverized pre-fired product, and sintering the body at 1100- 1200‹ C., the body being heated to the sintering temperature within 1 minute, maintained at this temperature for 1¢-8 minutes, and cooled to room temperature at substantially constant speed over 5-30 minutes. Pre-firing may be carried out at e.g. 600‹ C. in a fluidized bed. The body may be formed by compressing granules obtained by spray-drying an acetone suspension of pre-fired powder, or by punching a dried sheet made by casting on to a substrate a mixture of preferred powder with a binder. Acetone or binder may be removed by heating to 300‹ C.
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