The Effect of Addition Cu on the Appearance of Formation Ability and High Coercivity for Nd-Fe Metastable Phase by Using Short Drop Tube Process

Abstract

We have previously reported the undercooling solidification behavior and high coercivity(Hc) of the Nd Fe based metastable phase using various containerless processes. However, the mechanism of high coercivity of the metastable phase is unclear. In this study, we have intended to examine the effect of Cu addition on the formation and high coercivity of Nd Fe based metastable phase using close to the stoichiometric composition of the Nd 60 Fe 40 binary alloy. In addition, we have analyzed the relationship between high coercivity and the 3d 4f valence electron state by X ray photoelectron spectroscopy (XPS) analysis.The Nd Fe Cu ternary particle samples were found to solidify by the drop tube process. The coercivity which was 5.8×10 3 Oe, increased by about two fold after Cu addition. X ray diffraction (XRD) results showed that crystallization of the a Nd phase was markedly suppressed in the Nd 60 Fe 25 Cu 15 ternary particle samples. This is attributed to the increased production of the metastable phase by addition of Cu. The effectiveness of Cu addition on the formation of the metastable phase is suggested for this purpose. Using energy dispersive X ray analysis (EDS), the Nd Fe Cu ternary metastable phase composition ratio was found to be very similar to that of the Nd 60 Fe 25 Cu 15 ternary based material (Nd:Fe:Cu＝12:5:3).From the XPS result for the Nd 60 Fe 40 binary and Nd 60 Fe 25 Cu 15 ternary particle samples, the 3d 4f bonding energy shifted to lower energy by Cu addition. Therefore, it is suggested that high coercivity depends on the increase of the 3d 4f electron bonding energy strength by the addition of Cu. [doi:10.2320/jinstmet.JBW201509] (Received October 14, 2015; Accepted December 21, 2015; Published February 19, 2016) Keywords: droptube, neodymium iron alloy, metastable phase, high coercivity, 3d 4f valence electron state, X ray photoelectron spectroscopy (XPS) analysis