Effects of additives on hydrogen absorption and desorption characteristics of Nd(Fe,Mo)12 alloys

Effects of such additives as Co, Zr, Nb or Ga on hydrogen absorption and desorption characteristics of Nd(Fe,Mo)₁₂ alloys are investigated. It is found that Zr or Nb addition increases the disproportionation temperature of Nd(Fe,Mo)₁₂ alloys, and Co or Ga addition decreases the recombined temperature of its disproportionated products. This shows that Zr or Nb addition retards the disproportionation, while Co or Ga addition is effective for improving the recombination, which is similar to the effects of the additives on the hydrogen absorption and desorption characteristics of Nd₂Fe₁₄B alloys. However, according to X-ray diffraction (XRD) investigations for the magnetic-oriented samples, the final hydrogenation disproportiontation desorption recombination (HDDR) NdFe_10.5−XM_XMo_1.5 (M=Co, Zr, Nb or Ga) products are isotropic. The effects of additives on hydrogen absorption and desorption characteristics of Nd₂Fe₁₄B and Nd(Fe,Mo)₁₂ alloys are very similar, but the magnetic anisotropy of the final two HDDR products are different. In order to investigate this, similarities and differences of the two alloy systems and their corresponding HDDR phenomena are further studied. The results show that the formation of anisotropic powders may be related to the disproportionated products and crystal growth direction of the Nd₂Fe₁₄B and Nd(Fe,Mo)₁₂ system.