The effect of PrCuGa grain boundary diffusion on the magnetic properties and microstructure of sintered Nd-La-Y-Fe-B magnet

•The magnetic properties and microstructures of commercial Nd-La-Y-Fe-B permanent magnets grain boundary diffused with PrCuGa were systematically studied.•Both the Hcj and (BH)max of the magnets are obviously improved from 13.6 kOe, 32.2 MGOe to 18.3 kOe, 33.2 MGOe, respectively.•Pr enters into the main phases, leading to the increased HA and Ms of 2:14:1 phases. Ga and Cu elements in the grain boundary is advantageous to make the grain boundary phases clear and continuous, resulting in weakened exchange coupling interaction. Committed to acquiring cost-effective Nd-Fe-B based permanent magnets, commercial Nd-La-Y-Fe-B magnets had been grain boundary diffused with PrCuGa as the diffusion source. The optimized magnetic properties had been obtained when the magnet was annealed at 930 ℃. The Hcj and (BH)max increased from 13.6 kOe, 32.2 MGOe to 18.3 kOe, 33.2 MGOe respectively. The results show that the concentration of Pr in the grain boundary phase increases after the diffusion of PrCuGa, and the characteristic peak of the matrix magnet shifts to a large angle from the XRD pattern. Both Hcj and (BH)max are improved because Pr partially replaces La to from (Pr,Nd,La,Y)2Fe14B with higher intrinsic properties. In addition, Cu and Ga elements improve the continuity of the grain boundary phases and isolate the short-range exchange coupling between the main phase grains, contributing to the increased Hcj.