A sustainable route to high-performance Nd-Fe-B magnets using recycled feedstock and grain boundary design

Advanced grain boundary engineering through Zr-based additives has enabled a development in recycled Nd-Fe-B permanent magnet performance, achieving an intrinsic coercivity (Hcj) of 1930 kA/m at 20°C which is comparable to virgin magnet benchmarks. The enhanced magnetic architecture stems from the controlled formation of nanoscale ZrB 2 precipitates, which exhibit preferential growth along (001) planes, creating an optimized network of grain boundaries. Detailed microstructural characterization revealed various distinct intergranular phases, including Fe-Nd oxides and Co-Cu-rich regions, working synergistically to enhance magnetic isolation and structural stability. In this study, we distinguish between grain boundary (GB) regions, which separate Nd 2 Fe 14 B grains and serve as diffusion pathways, and intergranular (IG) phases, which form at grain junctions and play a role in magnetic isolation. The engineered grain boundary network, verified through comprehensive TEM and EDXS analyses, facilitates superior thermal stability with improved reversible temperature coefficients across operational temperature ranges. This validated recycling approach not only preserves but enhances critical magnetic properties, establishing a scalable pathway for producing high-performance magnets that meet the demanding requirements of electric mobility and renewable energy applications while addressing rare earth supply chain vulnerabilities.