Synthesis of Hard Magnetic Nd-Fe-B Powders by a Thermochemical Process
Fabrication of Nd-Fe-B magnetic powders by R-D process using spray-dried precursors was tried. Due to stable formation of a-Fe as a primary phase as same as that in ingots, the hard magnetic Nd<SUB>2</SUB>Fe<SUB>14</SUB>B phase was not formed in the alloy powder with the composition of stoichiometric Nd<SUB>2</SUB>Fe<SUB>14</SUB>B unless excessive amount of Nd precursor or Ca was added in the process. However, this excessive addition, especially for Ca, led to abnormal grain growth of Nd<SUB>2</SUB>Fe<SUB>14</SUB>B. On the contrary, Nd<SUB>2</SUB>Fe<SUB>14</SUB>B was successfully obtained as a major phase from the alloy powder with the composition of Nd<SUB>15</SUB>Fe<SUB>77</SUB>B<SUB>8</SUB> without such excessive addition. The size of spherical shape Nd<SUB>2</SUB>Fe<SUB>14</SUB>B particles mostly consisted of one or more subgrains was less than 1, um. The coercivity measured from this powder was relatively low (-3 kOe) mostly due to residual CaO and soft magnetic phases.
粉体および粉末冶金 50(11), 889-893, 2003-11-15
Japan Society of Powder and Powder Metallurgy