摘要
Iron-rich compounds with the tetragonal ThMn12-type structure have the potential to meet current demands for rare-earth-lean permanent magnets with high energy density and operating temperatures of 150-200℃.However,while it is normal for magnet technology to lag behind the development of underlying magnetic material,this gap has always been unusually large for ThMn12-type magnets.The gap has widened further in recent years,as excellent combinations of intrinsic magnetic properties have been obtained in compounds synthesized with a smaller amount of structure-stabilizing elements(e.g.,SmFe11V or Sm0.8Zr0.2Fe9.2Co2.3Ti0.5)or with no such elements(i.e.,SmFe9.6Co2.4 thin films).The search for promising compounds continues-with increasing help coming from theoretical calculations.Unfortunately,progress in the development of magnets beyond polymer-bonded interstitially modified powders remains marginal.The introduction of lanthanum(La)was found to stabilize low-meltingtemperature minority phases in Sm(Fe,Ti)12 alloys,thus allowing for liquid-phase sintering for the first time.The high reactivity of La,however,has apparently undermined the development of coercivity(Hc).A controlled crystallization of the initially suppressed ThMn12-type phase makes"bulk"magnetic hardening possible,not only in Sm-Fe-V alloys(in which it has been known since the 1990s),but also is in La-added(Ce,Sm)(Fe,Ti)12 alloys.The properties of the bulk-hardened alloys,however,remain unsatisfactory.Mechanochemically synthesized(Sm,Zr)(Fe,Si)12 and(Sm,Zr)(Fe,Co,Ti)12 powders may become suitable for sintering into powerful fully dense magnets,although not before a higher degree of anisotropy in both alloys and a higher Hc in the latter alloy have been developed.
基金
supported by the US Department of Energy,United States(DE-FG02-90ER45413)
EU Horizon 2020 Program(686056–NOVAMAG)
Ford Motor Company,United States.
作者简介
Corresponding author:A.M.Gabay,E-mail address:gabay@udel.edu.
