Microstructure Characterization and Magnetic Characteristics of Ce–Fe–B Based Spark Plasma Sintered Magnets

Abstract

Nanocrystalline Ce–Fe–B based rare earth permanent magnets are prepared by spark plasma sintering (SPS) method using grounded ribbons as raw material. The phase compositions, microstructure, magnetic properties, intergranular magnetic interactions, recoil loops, and corrosion resistance of the magnets are investigated systemically. The relationship among sintering processes, microstructures, and magnetic characteristics are discussed in depth by mainly using transmission electron microscope (TEM) and Physical Property Measurement System (PPMS) techniques. It is demonstrated that the sintering temperature has a significant influence on the average grain size and width of coarse grain areas. The optimized magnetic properties of remanent magnetization $J_{r}= 0.37$ T, coercivity $H_{\mathrm {ci}} = 227$ kA/m, and maximum energy product $(BH)_{\mathrm {max}}= 16$ kJ/m3 are obtained at 650 °C under 50 MPa for 2 min. Their exchanging coupling interactions are quite weak compared with those of the counterpart alloys. The exchanged decoupled of soft magnetic materials and inhomogeneous magnetic anisotropy result in open and steep recoil loops. The electrochemical experiment results display that the corrosion resistance of the magnets is improved by sintering at high temperature. This paper plays a role in guiding the future research and development of nanocrystalline Ce–Fe–B based permanent magnetic materials.