R-T-B Sintered Magnet Grain Boundary Diffusion for Coercivity

The patent applies local quality by concentrating heavy rare-earth elements (Dy, Tb) specifically at the grain boundaries of the R2T14B main phase through controlled diffusion, rather than uniformly distributing them throughout the entire magnet. This localized placement at grain boundaries provides the necessary coercivity enhancement while minimizing the overall heavy rare-earth content and preserving the bulk saturation magnetization, thus maintaining high remanence Br.

The patent employs parameter changes by precisely controlling the diffusion process parameters including temperature (700-950°C), time (0.5-4 hours), and heavy rare-earth element concentration (0.05-0.40 mass%) to achieve optimal coercivity enhancement. By adjusting these parameters, the patent optimizes the distribution and concentration of heavy rare-earth elements at grain boundaries, resolving the contradiction between improving HcJ and maintaining Br.

The patent minimizes heavy rare-earth element consumption by applying local quality - concentrating Dy or Tb exclusively at the grain boundaries through controlled diffusion rather than uniform distribution. This localized approach achieves maximum coercivity enhancement per unit of heavy rare-earth element used, as the grain boundary phase is where these elements most effectively influence magnetic domain wall pinning.

The patent applies partial action by introducing only the minimum necessary amount of heavy rare-earth elements (0.05-0.40 mass%) required to achieve the desired coercivity enhancement. Rather than saturating the entire magnet with heavy rare-earth elements, the diffusion process introduces just enough at the grain boundaries to achieve the technical effect, thereby reducing overall resource consumption.

The patent applies parameter changes by optimizing the heavy rare-earth element content to a specific range (0.05-0.40 mass%) that achieves sufficient temperature stability of coercivity without excessive resource consumption. This parameter optimization balances performance requirements with resource availability and cost considerations, making the magnet commercially viable while maintaining high-temperature performance.

The patent resolves the contradiction between temperature stability and resource availability by applying local quality - placing heavy rare-earth elements only where they are most effective (at grain boundaries) rather than throughout the bulk material. This localized strategy achieves the necessary temperature stability with minimal heavy rare-earth content, thereby maintaining adaptability to resource constraints and cost considerations.