Srフェライト焼結磁石の特性改良に関する研究

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Basic investigation on mechanisms of high densification, grain growth control and high-preferred orientation of Sr-ferrite sintered compact in the production process are performed. The high performance magnet has the composition of SrO⋅5.9Fe1O3, which is slightly deviated from that of the stoichiometric Sr-ferrite.CaO and SiO2 additives play important roles in the rapid densification and the grain growth control in the sintering process of Sr-ferrite compacts. The densification of the Sr-ferrite compact containing GaO and SiO2 additives is promoted by the presence of low melting liquid phase of the CaO-SiO2-SrO⋅6Fe2O3 system in the grain boundaries. The addition of small amount of SiO2, which is added to the raw material powder before calcining, can control the grain growth of Sr-ferrite particles and increase the intrinsic coercivity (iHc).In the presence of CaO additive, the SiO2 impurity causes the liquid phase sintering during the sintering process. The Al2O3 additive increases He by forming a solid solution with Sr-ferrite. In order to obtain higher degree of orientation, an improved parallel magnetizing circuit having uniformly distributed magnetic field strength is newly developed. By the analysis of the compressing mechanism of the Sr-ferrite fine particles, it is revealed that the preferred orientation process of the particles through the pressing in parallel magnetic field are considerably influenced by the average particle size and the particle size distribution. Based on these results, the highest quality magnets in current use are manufactured with high cost performance.
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Srフェライト焼結磁石の特性改良に関する研究

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