Phase Equilibria and Magnetic Phases in the Ce-Fe-Co-B System

Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS), and Magnetic Force Microscope (MFM) is used in this research to understand the phase equilibria and to explore promising magnetic phases in this system. Three magnetic phases were detected and their homogeneity ranges were determined at 900 °C, which were presented by the formulae: Ce(2)Fe(14−x)Co(x)B (0 ≤ x ≤ 4.76), CeCo(4−x)Fe(x)B (0 ≤ x ≤ 3.18), and Ce(3)Co(11−x) Fe(x)B(4) (0 ≤ x ≤ 6.66). The phase relations among the magnetic phases in this system have been studied. Ce(2)(Fe, Co)(14)B appears to have stronger magnetization than Ce(Co, Fe)(4)B and Ce(3)(Co, Fe)(11)B(4) from MFM analysis when comparing the magnetic interactions of selected key alloys. Also, a non-magnetic CeCo(12−x)Fe(x)B(6) (0 ≤ x ≤ 8.74) phase was detected in this system. A boron-rich solid solution with Ce(13)Fe(x)Co(y)B(45) (32 ≤ x ≤ 39, 3 ≤ y ≤ 10) chemical composition was also observed. However, the crystal structure of this phase could not be found in the literature. Moreover, ternary solid solutions ε(1) (Ce(2)Fe(17−x)Co(x) (0 ≤ x ≤ 12.35)) and ε(2) (Ce(2)Co(17−x)Fe(x) (0 ≤ x ≤ 3.57)) were found to form between Ce(2)Fe(17) and Ce(2)Co(17) in the Ce-Fe-Co ternary system at 900 °C.