High coercivity Pr2Fe14B/α-Fe nanocomposite permanent magnets with Zr addition

The ingots with nominal composition Pr9.5Fe84-xB6.4P0.1Zrx\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${ \Pr }_{9.5} {\text{Fe}}_{84 - x} {\text{B}}_{6.4} {\text{P}}_{0.1} {\text{Zr}}_{x}$$\end{document} (x = 0, 1, 2, 3) were prepared by an electric arc furnace under purified argon atmosphere. The ribbons were obtained by melt spinning at a wheel speed of 16-33 m center dot s(-1). X-ray diffraction (XRD) results show that P addition decreases crystallinity of hard phase, but further Zr addition increases the amorphous-forming ability of soft phase. The intrinsic coercivity largely increases from 502 (Zr-free) to 945 kA center dot m(-1) (2 at% Zr), which is among the highest value reported so far in this poor rare earth nanocomposite magnets. The hysteresis loops of the alloys with addition of 1 at% and 2 at% Zr show good squareness with single-phase characteristic, indicating well exchange coupling between hard and soft magnetic grains. Transmission electron microscope (TEM) results reveal small grain size and uniformity in the microstructure in the Zr-added samples, which is the reason for high coercivity.