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http://dx.doi.org/10.4283/JMAG.2009.14.1.027

High Coercive Nd-Fe-B Sintered Magnets for High Temperature Application  

Kim, D.H. (Jahwa Electronics Co.)
Kim, A.S. (Jahwa Electronics Co.)
Lim, T.H. (Department of Hybrid Engineering, Sunmoon University)
Jang, T.S. (Department of Hybrid Engineering, Sunmoon University)
Publication Information
Journal of Magnetics / v.14, no.1, 2009 , pp. 27-30 More about this Journal
Abstract
Various sintered magnets containing $28{\sim}31\;wt%$ Nd and $0{\sim}7\;wt%$ Dy were evaluated for coercivity and irreversible flux loss as a preliminary study to develop highly-coercive, high-temperature magnets that can be applied for driving motors in a hybrid vehicle. The sintered magnets were prepared in sequence of strip casting, HD treatment, jet milling, magnetic field pressing, sintering and post-annealing. Increasing Dy content and adjusting post-annealing temperature monotonically increased coercivity of magnets from about 14 kOe to 30 kOe. A magnet containing 28 wt% Nd and 7 wt% Dy exhibits a $(BH)_{max}$+$_i{H_c}$ value of almost 64. This is very close to what the automobile industry considers as the minimum value (65) for a hybrid vehicle system. Moreover, irreversible flux loss of the magnet was about 3% at $200^{\circ}C$, which is well less than the allowable limit (5%) to a driving motor in hybrid vehicles.
Keywords
Nd-Fe-B; coercivity; thermal stability; irreversible flux loss;
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