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Vol.18, No.3, 251 ~ 261, 1980
Title
A Study of the Effects of the Composition , and Sintering and Heat Treating Temperature on Magnetic Properties and Microstructures of SmCo5 Permanent Magnets
김성수Sung Su Kim, 윤용구Young Ku Yoon
Abstract
Effects of the composition, sintering temperature and heat treating temperature on magnetic properties of sintered SmCo_5 permanent magnets were investigated. SmCo_5 magnets heat treated at 900℃ and quenched exhibited the highest coercive force. This is believed to be due to the difficulty in nucleation of reverse domains without the Sm₂Co_(17) phase in the microstructure of the magnets and strong pinning of domain walls at grain boundaries where oxygen is segregated. The coercive force of the magnets decreased as the heat treating temperature was raised to higher temperatures (>900℃). This is attributed to the weaker pinning of domain walls at grain boundaries. The SmCo_5 magnets heat treated at lower temperatures (<900℃) exhibited lower coercive Force values than those exhibited by the magnets heat treated at 900℃. This lower coercive values are due to easier nucleation of reverse domains at the Sm₂Co_(17) phase that is formed as an eutectoid decomposition product below 800℃. SmCo_5 magnets whose total Sm content was 36wt.% exhibited the highest coercive force and also the greatest shrinkage. The SmCo_5 magnets with 36wt.% Sm content are of a hyperstoichiometric composition at which Co vacancy concentration is the maximum. The highest coercive force exhibited by the magnets containing 36wt.% Sm is attributed to the fact that the more the Co vacancy exists, the more the segregation of oxygen occurs at grain boundaries and the stronger the domain wall pinning is. The coercive force decreased as the sintering temperature was raised to higher temperatures. This decrease of the coercive force is attributed to the grain growth and ripening of inclusions and pores, since domain wall pinning at new grain boundaries become weaker.
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