Effect of Zr on the microstructure and magnetic properties of Sm(CobalFe0.1Cu0.088Zrx)8.5 magnets

The effect of Zr content on the microstructure and magnetic properties of Sm(CobalFe0.1Cu0.088Zrx)8.5 magnets with x varying from 0 to 0.1 was systematically studied using magnetic, x-ray diffraction, and transmission electron microscopy measurements. The results have revealed that addition of Zr greatly affects the microstructure and magnetic properties. X-ray diffraction, electron diffraction, and thermomagnetic data showed that the normal microstructure consists of 2:17 cells surrounded by 1:5 cell boundaries and intersected by lamella phase perpendicular to the c axis. The lamella phase appears to have the SmCo3 structure and its amount increases with increasing Zr content. When the Zr content is above 0.08, the microstructure becomes inhomogeneous, showing regions with a considerable amount of mixtures of 1:3 and 2:7 phases. The formation of the cellular microstructure mainly depends on the Cu content, and the existence of the lamellar phase can stabilize a uniform cellular microstructure with larger cells and help the redistribution of Cu at the cell boundaries, improving the coercivity greatly. A room temperature intrinsic coercivity of around 40 kOe has been obtained in magnets with a wide range of Zr contents from x=0.02–0.06.