Studies of new YDy-based R₂Fe₁₄B magnets for high temperature performance (R = Y + Dy + Nd)

The effect of Nd substitution on microstructure and magnetic properties in [Nd_x(YDy)_0.5(1-x)2.2Fe₁₄B ribbons melt-spun at 22 m/s has been systematically studied. As-spun ribbons with low Nd content consist of 2:17 and 2:14 :1 phases in an amorphous matrix, while as-spun ribbons with high Nd contain 2:14:1 and Fe phases in the amorphous matrix. After annealing at 700°C for 15 min, all of the ribbons exhibit only a single 2:14:1 phase in their X-ray diffraction patterns. Nd substitution can improve the maximum energy product of annealed ribbons but deteriorate the temperature stability of the ribbons. Increasing Nd (x) from 0 to 0.8, decreases coercivity from 22 to 13.5 kOe, but increases the maximum energy product from 5.87 to 11.2 MGOe. The temperature coefficients for remanence and coereivity increase from -0.045°C to -0.106 %/°C, and -0.306 to -0.38 %/°C, respectively for the same substitution range. Transmission electron microscope microstructures show that the samples with less Nd content exhibit a more uniform distribution of grains. Their average grain size is about 40 nm. The studied results show that the YDy-based R₂Fe₁₄B magnets are very promising for high-temperature performance.