CaF₂掺杂对热压SmCo₅/CaF₂复合磁体磁性能和电阻率的影响

Effect of CaF₂ Doping on Magnetic Properties and Resistivity of Hot-Pressed SmCo₅/CaF₂ Composite Magnet

为减小永磁电机中钐钴磁体的涡流损耗,本文通过高能球磨制备了CaF2掺杂的SmCo5/CaF2复合粉体,采用热压技术制备了SmCo5/CaF2复合磁体,研究了掺杂对热压复合磁体的微观组织、磁性能和电阻率的影响。结果表明,随着CaF2掺杂量的增加,CaF2逐渐呈现连续带状分布,实现了对SmCo5的绝缘包覆,使复合磁体的电阻率增大。当CaF2掺杂量为5 wt%时,复合磁体的电阻率为245 μΩ∙cm,当CaF2掺杂量为20 wt%时,复合磁体的电阻率高达680 μΩ∙cm,较未掺杂的SmCo5磁体电阻率75 μΩ∙cm提升了900%;但是,随CaF2掺杂量的增加,复合磁体的密度和磁性能呈现下降趋势,当CaF2掺杂量为5 wt%时,复合磁体的磁能积(BH)max由53.07 kJ/m3下降到42.83 kJ/m3,较未掺杂时下降了19%。当CaF2掺杂量为5 wt%时,随着CaF2预磨时间的延长,CaF2逐渐呈片状形貌,CaF2预磨5 h后所制备的SmCo5/CaF2复合磁体电阻率增大到283 μΩ∙cm,其磁能积(BH)max为42.82 kJ/m3。可见,当CaF2掺杂量相同时,延长预磨时间可以提高复合磁体的电阻率,而对其磁性能没有影响。

In order to reduce the eddy current loss of samarium cobalt magnets in permanent magnet motors, in this paper, SmCo5/CaF2 composite powders doped with CaF2 were prepared by high-energy ball grinding, SmCo5/CaF2 composite magnets were prepared by hot-pressed technology, and the effects of doping on the microstructure, magnetic properties and resistivity of hot-pressed composite magnets were studied. The results show that with the increase of CaF2 doping, CaF2 gradually presents a continuous zonal distribution, realizing the insulation coating of SmCo5, and increasing the resistivity of the composite magnet. When the CaF2 doping amount is 5 wt%, the resistivity of the composite magnet is 245 μΩ∙cm. When CaF2 is doped at 20 wt%, the resistivity of the composite magnet is up to 680 μΩ∙cm, which is 900% higher than that of the undoped SmCo5 magnet at 75 μΩ∙cm. However, with the increase of CaF2 doping amount, the density and magnetic properties of the composite magnet show a decreasing trend. When the CaF2 doping amount is 5 wt%, the magnetic energy product (BH)max of the composite magnet decreases from 53.07 kJ/m3 to 42.83 kJ/m3, which is 19% lower than that in the undoped condition. When the doping amount of CaF2 is 5 wt%, CaF2 gradually shows a flake morphology with the proflation of pregrinding time. The resistivity of SmCo5/CaF2 composite magnet prepared after 5 h pregrinding increases to 283 μΩ∙cm, and its magnetic energy product (BH)max is 42.82 kJ/m3. It can be seen that when the doping amount of CaF2 is the same, extending the pregrinding time can improve the resistivity of the composite magnet, but has no effect on its magnetic properties.