等方性Ca-La-Nd-(Sr)フェライト磁石の諸特性
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An experiment was carried out to investigate the preparation condition of isotropic Ca-La-Nd-(Sr) ferrite magnets with optimum magnetic and physical properties. Compositions, {92(CaO・6Fe_2O_3) 7 (70% La_2O_3)}, {92(CaO・6Fe_2O_3) 8 (70% La_2O_3)}, were chosen according to the formula {92(CaO_<1-y>SrO_y・6Fe_2O_3) 8 (70% La_2O_3)}, where y was varied between 0.1. 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 semi-sintered at 1000-1250℃ in O_2 gas for 1h. The resulting products were finely ground by ball-milling crusher, compacted into cylindrical specimens and then sintered at 1200-1300℃ in O_2 gas for 0.5h. The results are summarized as follows: 1) To obtain magnet having (BH) max. more than 8.0 kJ/m^3 in composition of {93(CaO・6Fe_2O_3) 7 (70% La_2O_3)} and {92(CaO・6Fe_2O_3) 8 (70% La_2O_3)}, semi-sintering at the temperature above 1200℃ is required. 2) The optimum condition of making magnets and magnetic properties of a typical specimens of isotropic Ca-La-Nd system ferrites are as follows, The preparation condition: composition {92(CaO・6Fe_2O_3) 8 (70% La_2O_3)}, semi-sintering condition 1225℃×1h in O_2 gas, sintering condition 1250℃×0.5h in O_2 gas. Magnetic properties: Im=0.370T. Ir=0.255T, _IH_C=165.5kA/m, _BH_C=131.3kA/m, (BH) max.=10.35kJ/m^3. 3) In the formula {92(CaO_<1-y>SrO_y・6Fe_3O_3(70% La_2O_3)}, the magnetic properries of these magnets were aprarently imppoved by substitution of SrO for a part of the component oxides, Moreover, curie temperature increased with the increase of y value. 4) Isotropic Ca-La-Nd-Sr system ferrite magnets semi-sintered at 1000℃ were equivalent to ordinary Ba and Sr ferrites in thier magnetic properties.
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