Preparation of anisotropic permanent magnets

A.L. Stuyts (Inventor), A.H. Hoekstra (Inventor), G.H. Weber (Inventor), G.W. Rathenau (Inventor)

Research output: PatentPatent publication


A permanent magnet with the formula MO.6Fe2O3 is prepd. from Fe polyoxides, M = Ba, Sr, or Pb with hexagonal structure, and 0.01-1 wt. % modifying agent selected from Ca, La, W, As, Sb, and B oxides or other compds. which can be converted to oxides on heating. The material is compressed in a press magnet by application of d.c. voltage and sintered at 1150-1350 Deg. Thus, a mixt. of BaCO3 341 g. and Fe oxide 1661 g. is ball milled with 5 wt. % H2O, compressed into tablets, sintered at 1270 Deg, and cooled to 1200 Deg. The practice is repeated several times at different heating and cooling rates. The tablets are ball milled with alc. and mixed with 0.25 wt. % La2O3 and compressed with a press magnet. The tablets are heated in a continuous heating furnace at 10 mm./min. and sintered 10 min. at 1320 Deg. The tablets have d. 4.58 g./cm.3, Br 3400 gauss, IHc 2080 oe., BHc 1950 oe., and BHmax. 2.52 * 106 gauss-oe., as compared to 4.37, 3340, 1700, 1590, and 2.35 * 106 for pellets contg. no modifier and sintered at 1300 Deg. [on SciFinder (R)]
Original languageEnglish
Publication statusPublished - 22 Jul 1965


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