The effect of Pr and Zr substitutions on the disproportionation reaction in Nd-Fe-B-based materials

A range of ten Pr- and Zr-containing Nd-Fe-B-based alloy samples were disproportionated in a flow of hydrogen gas using a specially modified vibrating-sample magnetometer. The magnetization of the samples was measured as a function of temperature in order to monitor the changes taking place in the material during the hydriding and disproportionating reactions. The disproportionation reaction, which results in the formation of iron, was observed to vary significantly, depending on the zirconium content of the alloy. Substituting praseodymium for neodymium also had an effect on the progress of the disproportionation reaction, with two-stage behavior being replaced by a single-stage reaction as more praseodymium is added at the expense of neodymium. The intrinsic coercivities of bonded magnets produced from HDDR powders demonstrated that small substitutions of zirconium can substantially increase the coercivity providing that not too much zirconium is added, and that almost completely substituting the neodymium in the alloy with praseodymium leads to the best coercivities.