High coercivity Pr2Fe14B magnetic nanoparticles by a mechanochemical method

Nd2Fe14B nanoparticles are widely used because of their outstanding hard magnetic properties. In fact, Pr2Fe14B has higher magneto-crystalline anisotropy than Nd2Fe14B, which makes Pr-Fe-B a promising magnetic material. However, the chemical synthesis route to Pr2Fe14B nanoparticles is challenging because of the higher reduction potential of Pr3+, as well as the complex annealing conditions. In this work, Pr2Fe14B nanoparticles were successfully synthesized via an efficient and green mechanochemical method consisting of high energy ball milling, annealing, and a washing process. Microstructural investigations revealed that the oxide precursors were uniformly wrapped by CaO and CaH2, which formed an embedded structure after ball milling. Then, Pr2Fe14B powder was synthesized via a time-saving annealing process. The impact of the Pr2O3 content and the preparation conditions was investigated. The coercivity of the as-annealed powder with 100 wt% Pr2O3 excess is 18.9 kOe. After magnetic alignment, the coercivity, remanence, and maximum energy product were: 9.8 kOe, 78.4 emu g−1, and 9.8 MGOe, respectively. The present work provides a promising strategy for preparing anisotropic Pr-Fe-B permanent magnetic materials.