Influence of Addition of Some Oxides on the Magnetic Properties of the Strontium Ferrite Magnets Takeshi Anbo, Takahiro Motone, Takashi Furuya and Koichi Sasaki Synopsis Recently high coercivity ferrite magnets have been demanded for stors or rotors of motors and generors. We took up the anisotropic strontium ferrite magnets pressed in wet for above request and studies the influence of the addition of some oxides such as SiO2, K2O, Li2O, MgO, BaO and Bi2O3 on the magnetic properties. Addition of SiO2 delays the sintering reaction and decreases the degree of oriention each sintering temperure below 1300 Ž. Remanence Br and maximum energy product (BH)max decrease slightly with increase of SiO2, but coercive force BHC rises excellently. For instance, 0.25 `0.6wt% SiO2, BHC more than 3,000 Oe was obtained with Br 3,900 `4,000 G and (BH)max 3.3 `3.7 MGOe. Duplex addition of SiO2 and K2O increases BHC and duplex addition of SiO2 and BaO increases Br and (BH)max respectively.
Table 1. Chemical composition of Fe203 and SrCO3 used for experiment. Fig. 1. Process of preparion of the specimen.
Fig. 2. Relion between magnetic properties and mol rio (Fe2O3/SrO) of strontium ferrite magnets with 0.4wt% SiO2, sintered 1,240 Ž for 60 minutes. Fig. 3. Influence of average size of perticles pulverized on magnetic properties and density of strontium ferrite magnets with 0.25wt% SiO2 and mol rio 5.6, sintered 1,250 Ž for 60 minutes. Fig. 4. Change in magnetic properties and density with sintering temperure, for strontium ferrite magnets with no-sio2 and mol rio 5.6, sintered each teperure for 60 minutes.
Fig. 5. Change in magnetic properties and density with sintering temperure, for strontium ferrite magnets with 0.25wt% SiO2 and mlo rio 5.6, sintered each temperure for 60 minutes. Fig. 6. Change in magnetic properties and density with sintering temperure, for strontium ferrite magnets with 0.6wt% SiO2 and mol rio 5.6, sintered each temperure for 60 minutes.
Fig. 7. Effect of SiO2 addition on magnetic properties and density of strontium ferrite magnets with mol rio 5.6, sintered 1,240 Ž for 60 minutes. Fig. 8. Change of oriention rio f of grains aligned to k00l l direction by X-ray analysis against sintering temperure for strontium ferrite magnets with mol rio 5.6, sintered each temperure for 60 minutes.
156 電気製鋼 Perpendicular to the pressing direction 1,200 1,250 1,300 Photo. 1. Microphotographs 第2号 Paralel to the pressing direction of 第48巻 sintered strontium ferrite magnets 1,200 1,250 1,300 with no-sio2. ( ~800)
昭 和52年4月(1977) 157 Perpendicular Photo. 2. to the pressing direction Paralel to the pressing direction 1,200 1,200 1,250 1,250 1,300 1,300 Microphotographs of sintered strontium ferrite magnets with 0.25wt% SiO2. ( ~800)
Fig. 9. Relion between magnetic properties and rio of oriention of grains aligned to k00l l direction in strontium ferrite magnets with mol rio 5.6. Fig. 10. Influence of Li2O, K2O and MgO addition on magnetic properties of strontium ferrite magnets with 0.3wt% SiO2 and mol rio 5.6 sintered 1,250 Ž for 60 minutes.
Fig. 11. Influence of Bi2O3 and BaO addition on magnetic properties of strontium ferrite magnets with 0.4wt% SiO2 and mol rio 5.6 sintered 1,240 Ž for 60 minutes. 1) H. Kojima: Sci. Rep. RITU, A-10 (1958), 175 2) A. Cochardt: J. Appl. Phys. 38 (1967) 4, 904 3) A. Cochardt: J. Appl. Phys. 34 (1963) 4, 273 4) F.K. Lotering: J. Inorg. Nucl. Chem., 9 (1959), 113 6) A.L. Stuijts: Trans. Brit. Cer. Soc., 55 (1956), 57