Synthesis of high-energy-density Pr₂Fe_14-xCo_xB, x≤3, magnets for practical applications

Abstract

Stable magnetic powders, of 1-2μm particle size, of partially co-substituted, Pr₂Fe_14-xCo_xB, x≤3, alloys together with 2-4 at% excess Pr were prepared by rapidly quenching the associated melts into thin ribbons and then mechanical attriting the ribbons in the refined particle sizes. The saturation magnetization M_s, remanent magnetization J_r, intrinsic coercivity H_ci and Curie temperature T_c were studied in characterizing the powders for fabricating into sintered or polymer bonded magnets. It is found that the small x=0·4-0·8 substitution of the Co on Fe sites in this series sensitively leads to an increase in the value of H_ci, by as much as 40%, with the optimum value of 21 kOe at x ~ 0·55, together with an improvement in the T_c from 292°C to 325°C, without significantly diluting the M_s ~ 150 emu/g and J_r ~ 8·0 kG values. The co-substituted Pr₂Fe₁₄B alloy particles are better stable and corrosion resistant in ambient atmosphere. The results are discussed with the microstructure and comparison with the data for Nd₂Fe₁₄B powders processed under the same conditions.