Grain Boundary Diffusion

Grain Boundary Diffusion (GBD) in permanent magnets is the process of distributing heavy rare-earth elements into the intergranular material which is wrapped around the grains of a sintered magnet. This process increases the coercivity (Resistance to demagnetization) of the magnet without compromising the induction strength (Br) of the magnet.

The permanent magnets are coated with a thin layer of heavy rare earth metal (HRE) and then undergo special heat treatment. This allows us to create smaller and thinner magnets that have higher resistance to opposing magnets or coils without the risk of demagnetization. Grain Boundary Diffusion (GBD) process is an effective approach for enhancing coercivity with low material cost.

Figure 1. 1 H curves before and after GBD

 

Stanford Magnets adopts the following two methods:

• Spray method
• Physical Vapor Deposition – PVD method