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

摘要: 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。

Abstract: In order to reduce the eddy current loss of samarium cobalt magnets in permanent magnet motors, in this paper, SmCo_5/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.