Preparation of Fe₃B+Nd₂Fe₁₄B Powder with Fine Grain and its Magnetic Properties

Abstract

Amorphous powders with composition (Fe₃B)1-X(Nd₁₆Fe₇₈B₆)X(0.250≤X≤0.438) were prepared by mechanical alloying (MA) for 30h in Ar. These MA'ed powders were heat treated for crystallization at 873-973K in vacuum, and their magnetic properties were studied in connection with the composition and the heat treatment temperature. The optimum heat treatment temperature was found to be at 893K, where the specimen was composed of the hard magnetic phase of Nd₂Fe₁₄B, and the soft magnetic phases of Fe₃B and a -Fe. The coercivity increased with increasing Nd concentration, while the saturation magnetization decreased with increasing Nd concentration. The coercivity of 2.80kOe and saturation magnetization of 144emu⋅g^-1 were obtained in the 5.0 at% Nd specimen. TEM photograph showed that the grain size of crystallized powders was about 30nm, irrespective of Nd concentration.