Hydrogen absorption and desorption behavior in Pr–Fe–B type alloys

Abstract

In this study, the hydrogen absorption and desorption behavior of Pr–Fe–B type alloys with addition of Co, Ga, and Zr was investigated focusing on the disproportionation and recombination reaction in HDDR process. In Pr13B6Febal. alloy, the second hydrogen absorption reaction which corresponds to the disproportionation reaction in HDDR process occurs at about 620 °C, and the recombination reaction was not observed below 1000 °C in hydrogen atmosphere. In alloys with Co content of 12 at.%, the second hydrogen desorption reaction, which corresponds to the recombination reaction in HDDR process, occurs at about 955 °C and the occurring temperature of the recombination reaction is further decreased with increasing Co content. The Ga addition to Pr13B6Febal. alloy also reduces the recombination reaction temperature and has no significant influence on the disproportionation reaction. Moreover, the lowering of the recombination reaction temperature is remarkable when Ga and Co are added simultaneously. On the contrary, Zr addition to Pr13B6Febal. alloy may not cause the recombination reaction but make the disproportionation reaction sluggish. The Pr–Fe–B type magnet powder which has a remanence of 9.8 kG and coercivity of 4.8 kOe, was obtained by HDDR treatment.