The reduction-diffusion process using Ca as reducing agent has been practiced industrially in the production of the SmCo5 type, the Nd-Fe-B type and the Td-Fe-Co type magnetic materials. The advantages of the R-D process are the generally high yield of rare earth metals and the single-stage conversion of mixture of oxides and metal powders into a product of rare earth alloy powders. On the other hand, its disadvantages are the slightly high contents of O and Ca. These disadvantages are remarkable in the Nd-Fe-B type. An experimental study was carried out on oxygen and calcium reduction technique for Nd-Fe-B alloy powders produced by reduction-diffusion method using metallic Ca as reductant. One technique is to dope Co or Ni into the raw powders, and another is to reduce Nd content from the atomic ratio of Nd15Fe77B8. These alloy powders are suitable for the production of Nd-Fe-B sintered magnets and are expected higher magnetic properties.
