異方性Ca-La-Nd-Srフェライト磁石の研究

概要

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Experiments were carried out to investigate the optimum conditions for preparing anisotropic Ca-La-Nd-Sr ferrite magnets having the best magnetic and physical properties. Compositions were chosen according to the formula {100-X(CaO・6Fe_2O_3)}{X(70%La_2O_3)} and {92(CaO_<1-y>SrO_y・6Fe_2O_3)}{8(70%La_2O_3)}, where X was varied between 0 and 13wt%, and y between 0 and 1.0. The samples used in these experiments were prepared by mixing of raw materials of α-Fe_2O_3, CaCO_3, 70%La_2O_3 (containing 20%Nd_2O_3), and SrCO_3 powder. The mixtures were semisintered at 1175〜1225℃ in O_2 gas for 1h. The resulting products were finely ground by a ball-milling crusher, compacted into cylindrical specimens in the magnetic field and then sintered at 1200〜1300℃ in O_2 gas for 0.5h. The results can be summarized as follows: (1) In the formula {(100-X)(CaO・6Fe_2O_3)}{X(70%La_2O_3)}, it was shown that magnets containing 7〜9wt% 70%La_2O_3 were equivalent to Ba and Sr ferrite in their magnetic properties. (2) In the formula {92(CaO_<1-y>SrO_y・6Fe_2O_3)}(8(70%La_2O_3)}, the magnetic properties of these magnets were apparently improved by substitution of SrO for a part of the component oxides. Moreover, their coercive force and curie temperature increased with the increase of y value. Ca-La-Nd-Sr system ferrite having the value of (BH) max. 28.4〜29.4 kJ/m^3 could be prepared by a standard manufacturing technique.