Magnetic properties and resistivity of a 2:17-type SmCo magnet doped with ZrO₂

In order to counteract the demagnetization caused by eddy current loss, widespread attention has been devoted to increasing the resistivity of permanent magnets. We prepared 2:17-type SmCo magnets doped with different ZrO₂ contents and investigated the influence of the ZrO₂ content on the magnetic properties and resistive anisotropism. The results showed that not only was the resistivity of the magnet improved, but, in addition, the coercivity of the magnet was significantly increased. The microstructure was studied with TEM, which showed that ZrO₂ doping was able to cause a decrease in the lamellar phase density and the growth of cellular structures. The increased grain boundaries and Sm₂O₃ phases were favorable to the improvement of resistivity. The decrease of the lamellar phases caused a narrowing of the resistive anisotropism. The additional Cu in the center of the cellular boundaries was the main reason for the enhancement of H_cj. However, an excessive amount caused an increase of the Zr₆(FeCo)₂₃ phase and a deterioration of the cellular structure, thereby leading to a decrease in coercivity.