Studies on low rare earth Nd-Fe-B compositions

Investigations have been carried out to evaluate the optimum Nd-Fe-B composition to have H_ci of at least 4 kOe. The optimum composition for the best magnetic properties is as follows: TRE 18 wt.%, B 1 wt.% and balance Fe. The magnetic properties are B_r , 10.1 kG, H_ci 4.3 kOe and BH_max 12.5 MGOe. All the additives (Ga, Nb, Mo, V, Cr) with or without cobalt addition did not improve the magnetic properties. The bonded magnets made using this material had B_r value slightly higher than the standard MQP-B powder. The low coercivity of these materials limit their operating temperature to 80°C. This material having Nd₂Fe ₁₄B/∝-Fe shows improved saturation behavior compared to those having Nd₂Fe₁₄B/Fe₃B and Nd₂ Fe₁₄B structures. It would then be a good candidate for applications where magnetization is difficult