Abstract
In this work, an experiment was carried out to investigate the preparation condition of anisotropic, Fe-deficient, M-type Sr ferrite with optimum magnetic and physical properties by changing experimental parameters, such as the La substitution amount and little additive modification during fine milling process. The compositions of the calcined ferrites were chosen according to the stoichiometry LaxSr1-xFe12-2xO19, where M-type single-phase calcined powder was synthesized with a composition of x = 0.30. The effect of CaCO3, SiO2, and Co3O4 inter-additives on the Sr ferrite was also discussed in order to obtain low-temperature sintered magnets. The magnetic properties of Br = 4608 Gauss, bHc = 3650 Oe, iHc = 3765 Oe, and (BH)max = 5.23 MGOe were obtained for Sr ferrite hard magnets with low cobalt content at 1.7 wt%, which will eventually be used as high-end permanent magnets for the high-efficiency motor application in automobiles with Br > 4600 ± 50 G and iHc > 3600 ± 50 Oe.
Highlights
Hexagonal magneto-plumbite-type strontium ferrite (SrFe12 O19 ) has material characteristics, such as a stable crystal structure, high coercivity and magnetic energy product, and magnetic anisotropy (K1 ) [1], so it is widely used in permanent magnet motors and various electronic devices, which is an important basic functional material in the electronics industry
CaCO3 and SiO2, the amount of Co3 O4 doped as the secondary additive after calcining is little, allowing it to be more economical to modify the magnetic properties of Sr ferrite and enhance mass production
La Sr substituted for Srferrite in theon calcined ferrite properties, a non-stoichiometric formula composed of La xSr1-xFe12-2x
Summary
Hexagonal magneto-plumbite-type strontium ferrite (SrFe12 O19 ) has material characteristics, such as a stable crystal structure, high coercivity and magnetic energy product, and magnetic anisotropy (K1 ) [1], so it is widely used in permanent magnet motors and various electronic devices, which is an important basic functional material in the electronics industry. CaCO3 and SiO2 , the amount of Co3 O4 doped as the secondary additive after calcining is little, allowing it to be more economical to modify the magnetic properties of Sr ferrite and enhance mass production. Co3 O4 with two other important additives, CaCO3 and SiO2 , added after calcining instead of during the calcination step to satisfy customers’ need for permanent ferrite magnet with high performance, low material prices, small batch production, easy manufacturing, large process-adjusting windows, and excellent economy. Our experimental results found that with a Fe-deficient calcined formula with a “Cobalt-free” recipe design and optimized process parameters, magnetic performance was obtained as follows: Br = 4608 Gauss, b Hc = 3710 Oe, i Hc
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