Strategy for Co‐Enhancement of Remanence–Coercivity of RE‐Fe‐B Sintered Magnets with High Ce‐Content: Appropriate La Substitution

Abstract

The development of low-cost RE-Fe-B sintered magnets with large La/Ce content is of great significance for the balanced utilization of rare earth (RE) resources, but it is limited by reduced magnetic properties. In this work, the coercivity (H cj ), remanence (B r ), maximum energy product [(BH) max ], and temperature stability are simultaneously enhanced for magnets with LaCe accounting for 40 wt% of the total RE. The synergistic regulation of the REFe 2 phase, Ce-valence, and grain boundaries (GBs) in RE-Fe-B sintered magnets is realized for the first time by introducing appropriate La elements. The La elements inhibit the generation of the REFe 2 phase and tend to stay in the triple junctions, promoting the segregation of the RE/Cu/Ga elements and contributing to the formation of Ce/Nd/Cu/Ga-rich continuous thicker lamellar GBs, and as a result, weakening the detrimental effect on HA caused by La element substitution and enhancing H cj . In addition, partial La atoms entering the RE 2 Fe 14 B phase are beneficial for improving the B r and temperature stability of the magnets and promoting the Ce 3+ ion ratio, which also provides additional benefit for B r . The findings provide an effective and feasible way to co-enhance the remanence and coercivity of RE-Fe-B sintered magnets with high Ce content.

Improvement of the microstructure and magnetic properties of (La,Ce)–Fe–B nanocrystalline ribbons

“…[21] In addition, as the La content increased, fractions of the rare earth-rich phase and the CeFe 2 phase decreased, strengthening the exchange coupling effect between matrix phase grains. [17] The large segregation area of the β -La phase would generate poor GBs between matrix grains, [4] and they may act as nucleation sites for the reverse magnetization domains and worsen the H cj of ribbons.…”

“…To curb the cost of permanent magnet production, the cost-effective Ce-Fe-B [1][2][3] and (La,Ce)-Fe-B [4][5][6][7][8][9] rare earth permanent magnets have attracted wide attention. Herbst et al [10,11] and Soeda et al [12] reported the hard magnetic properties of Ce 2 Fe 14 B and (La,Ce) 2 Fe 14 B compounds, respectively.…”