Effect of niobium substitution on microstructures and thermal stability of TbCu7-type Sm-Fe-N magnets
来源期刊：Journal of Rare Earths2018年第3期
论文作者：Guiyong Wu Hongwei Li Dunbo Yu Kuoshe Li Wenlong Yan Chao Yuan Liang Sun Yang Luo Kun Zhang
文章页码：281 - 286
摘 要：This paper reports crystal structures, magnetic properties and thermal stability of TbCu7-type Sm8.5Fe(（85.8-x）Co4.5Zr1.2Nbx（x = 0-1.8） melt-spun compounds and their nitrides, investigated by means of X-ray diffraction, vibrating sample magnetometer, flux meter and transmission electron microscope. It is found that the lattice parameter ratio c/a of TbCu7-type crystal structure increases with Nb substitution, which indicates that the Nb can increase the stability of the metastable phase in the Sm-Fe ribbons. Nb substitution impedes the formation of magnetic soft phase a-Fe in which reversed domains initially form during the magnetization reversal process. Meanwhile, Nb substitution refines grains and leads to homogeneous micro structure with augmented grain boundaries. Thus the exchange coupling pining field is enhanced and irreversible domain wall propagation gets suppressed. As a result, the magnetic properties are improved and the irreversible flux loss of magnets is notably decreased. A maximum value 771.7 kA/m of the intrinsic coercivity Hcj is achieved in the 1.2 at% substituted samples.The irreversible flux loss for 2 h exposure at 120 ℃ declines from 8.26% for Nb-free magnets to 6.32% for magnets with 1.2 at% Nb substitution.
Guiyong Wu1，Hongwei Li1，Dunbo Yu1，Kuoshe Li1，Wenlong Yan1，Chao Yuan1，Liang Sun1，Yang Luo1，Kun Zhang1,2
1. National Engineering Research Center for Rare Earth Materials,General Research Institute for Nonferrous Metals,Grirem Advanced Materials Co.Ltd.2. Key Laboratory of Microgravity(National Microgravity Laboratory),Institute of Mechanics,Chinese Academy of Sciences
摘 要：This paper reports crystal structures, magnetic properties and thermal stability of TbCu7-type Sm8.5Fe(（85.8-x）Co4.5Zr1.2Nbx（x = 0-1.8） melt-spun compounds and their nitrides, investigated by means of X-ray diffraction, vibrating sample magnetometer, flux meter and transmission electron microscope. It is found that the lattice parameter ratio c/a of TbCu7-type crystal structure increases with Nb substitution, which indicates that the Nb can increase the stability of the metastable phase in the Sm-Fe ribbons. Nb substitution impedes the formation of magnetic soft phase a-Fe in which reversed domains initially form during the magnetization reversal process. Meanwhile, Nb substitution refines grains and leads to homogeneous micro structure with augmented grain boundaries. Thus the exchange coupling pining field is enhanced and irreversible domain wall propagation gets suppressed. As a result, the magnetic properties are improved and the irreversible flux loss of magnets is notably decreased. A maximum value 771.7 kA/m of the intrinsic coercivity Hcj is achieved in the 1.2 at% substituted samples.The irreversible flux loss for 2 h exposure at 120 ℃ declines from 8.26% for Nb-free magnets to 6.32% for magnets with 1.2 at% Nb substitution.
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