Spark plasma sintering Fe3B/(Pr,Tb)2Fe14B bulk nanocomposite permannet magnets

In this paper, the microstructure and magnetic properties of the Fe₃B/(Pr,Tb)₂Fe₁₄B nanocomposite permanent magnets obtained from melt-spun powders with composition of Pr_4.2Tb_0.3Fe₇₈B_17.5 by applying spark plasma sintering (SPS) was discussed. Since the magnetic properties such as remanence (Br) and coercivity (Hci) will deteriorate dramatically due to excessive grain growth during sintering process. An important advantage of SPS is its high sintering speed, which can effectively restrain the grain growth and allows the formation of fine crystalline materials with full density in a short time. Hence, it was considered that the exchange coupling between magnetically hard and soft phase maintained during the densification. The average grain size of the sample consolidated at 973 K, however, reached 50 nm, which was suggested to be responsible for the decrease of both Br and Hci of the magnets. The XRD, TEM and SAED pattern of samples consolidated at various temperatures like 898 and 923 K were obtained respectively.