High coercivity Pr₂Fe₁₄B magnetic nanoparticles by a mechanochemical method

Area of Science:

• Materials Science
• Nanotechnology
• Magnetism

Background:

• Neodymium-iron-boron (Nd₂Fe₁₄B) nanoparticles are key hard magnetic materials.
• Praseodymium-iron-boron (Pr-Fe-B) offers superior magneto-crystalline anisotropy but faces synthesis challenges.
• Higher reduction potential of Pr³⁺ and complex annealing hinder Pr-Fe-B nanoparticle production.

Purpose of the Study:

• To develop an efficient and green synthesis route for Pr₂Fe₁₄B nanoparticles.
• To investigate the impact of Pr₂O₃ content and preparation conditions.
• To provide a viable strategy for producing anisotropic Pr-Fe-B permanent magnets.

Main Methods:

• Utilized a mechanochemical approach involving high-energy ball milling, annealing, and washing.
• Employed CaO and CaH₂ to encapsulate oxide precursors during ball milling.
• Optimized annealing time and Pr₂O₃ excess for Pr₂Fe₁₄B formation.

Main Results:

• Successfully synthesized Pr₂Fe₁₄B nanoparticles via a green mechanochemical route.
• Observed uniform encapsulation of oxide precursors by CaO and CaH₂ after milling.
• Achieved a coercivity of 18.9 kOe for as-annealed powder with 100 wt% Pr₂O₃ excess.
• Obtained aligned magnetic properties: 9.8 kOe coercivity, 78.4 emu g^-1 remanence, and 9.8 MGOe maximum energy product.

Conclusions:

• The mechanochemical method is an efficient and green strategy for Pr₂Fe₁₄B nanoparticle synthesis.
• This method overcomes previous limitations associated with Pr³⁺ reduction and annealing.
• The produced Pr-Fe-B materials show promise for applications requiring high-performance permanent magnets.