MICROSTRUCTURE STUDY OF HIGH COERCIVITY GA CONTAINING ND-FE-B PERMANENT-MAGNETS

Recently we reported that substitution of 1 at% of Fe by Ga in a Nd18F e76B6 alloy led, in some cases, to an increase in coercivity by a fact or of 2 (to > 46 kOe) for chill block melt spun ribbons. In this paper a microstructural investigation by high resolution transmission elect ron microscopy of the Ga-containing ribbons is reported. It was observ ed that the Ga entered only the Nd2Fe14B hard magnetic phase with no e vidence of its presence in the Nd-rich grain boundary phase. Ultra fin e particles of similar to 5 nm mean diameter were observed within the Nd2Fe14B crystallites and these have been identified as rhombohedral g allium by analysis of lattice images. The possible reasons for the inc reased coercivity are briefly discussed.