The magnetic properties, thermal stability and microstructure of Nd-Fe-B/Ga sintered magnets prepared by blending method

The effect of gallium added by blending method on the magnetic properties, thermal stability and microstructure of Nd16.5Dy16.0Fe53.45Co13.0B1.05 (wt% ) sintered magnets was investigated. The experimental results show that an appropriate Ga. addition can markedly increase the coercivity. reduce the i rreversible loss and slightly enhance the remanence. For instance, by addin g 0.5 wt% Ga, the coercivity is increased from 1232 to 1819 kA/m, the irrev ersible loss after being exposed at 200 degreesC for 0.5 It is reduced from above 33% to below 5%. Microstructure analyses show that the grain boundar ies of the magnets with and without Ga addition are substantially different . The grain boundaries of the Ga-free magnet are meandrous. On the other ha nd, most of the boundaries of Ga-containing magnets are straight and smooth . These characteristics can be explained by the appearance of new phases du ring sintering process. (C) 2001 Elsevier Science B.V. All rights reserved.