熱処理-再粉砕法によるSrフェライト焼結体の作製

概要

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Effects of milling conditions and particle size of Sr-ferrite powder on microstructure and magnetic properties of sintered Sr-ferrite have been investigated. Processes for obtaining a fine Sr-ferrite powder have direct effects upon the crystallite size and its distribution of sintered Sr-ferrite specimens. As a result of new improved processing for obtaining fine powders having a narrow particle size distribution, both Br and iHc of sintered Sr-ferrite specimens increased. Probably, these phenomena are related to the increase in the amount of crystals having magnetic single domain. To improve the particle size distribution of Sr-ferrite powder in the milling process, a new process consisting of three steps, i.e., primary milling, annealing and remilling, has been studied. In this process, annealing makes submicron particles grow into spherical particles of about 1 μm. In the subsequent remilling process, residual coarse particles of more than 2 μm can be milled selectively into fine particles. Consequently, the new annealing-remilling process gives Sr-ferrite powders with more uniform particle size distributions than the conventional milling process, resulting in success of fabricating high-performance sintered Sr-ferrite magnets having ≧Br0.44T, ≧iHc287kA/m, (BH)≧max37.4 kJ/m^3 or ≧Br0.42T, ≧iHc334 kA/m, (BH)≧max34.2 kJ/m^3.
社団法人日本セラミックス協会の論文
1993-08-01