Effect of annealing on microstructural changes of Nd-rich phases and magnetic properties of Nd-Fe-B sintered magnet

Abstract

The microstructural changes of Nd-rich interface phases during postsintering annealing were investigated. A mixture of very fine (about 2-3 nm) crystallites of hexagonal h-Nd(2)O(3), cubic Ia (3) over bar -Nd(2)O(3) (C-Nd(2)O(3)), and amorphous phases were observed at the interface phase in the as-sintered magnet and after the first postsintering annealing process. The transformation from h-Nd(2)O(3) to C-Nd(2)O(3) occurred during the second postsintering annealing process, and the resulting C-Nd(2)O(3) has the proper crystallographic relation with the main phase. The reduced lattice mismatch between the (110) plane of C-Nd(2)O(3) interface phase and the (001) or (100) plane of Nd-Fe-B main phase after the second postsintering annealing process is the primary reason for the enhancement in the magnetic properties. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3348479]