The reaction mechanism of formation of chemically synthesized Nd2Fe14B hard magnetic nanoparticles.
Deheri, P. K.
Ramanujan, Raju V.
Date of Issue2011
School of Materials Science and Engineering
Nd2Fe14B based magnetic materials exhibit excellent magnetic properties and are widely used in many engineering applications. However, chemical synthesis of this compound is challenging. In this work, the formation mechanism of chemically synthesized Nd2Fe14B magnetic nanoparticles was studied. Nd, Fe and B precursors were converted to Nd–Fe–B oxide by the sol–gel method, reduction of these oxides by CaH2 resulted in Nd2Fe14B nanoparticles. Nd2Fe14B phase formation resulted from two competing reactions: (a) Nd2Fe14B phase formation by direct combination of NdH2, Fe and B, (b) Nd2Fe17 phase formation from NdH2 and Fe, followed by Nd2Fe14B phase formation by the reaction of Nd2Fe17 and B. Addition of boron to Nd–Fe–B oxide during reduction resulted in improved magnetic properties. The activation energy for Nd2Fe14B phase formation was found to be 365 kJ mol−1. The optimum heat treatment temperature and time for Nd2Fe14B phase formation were found to be 800 °C and 90 min, respectively.
Journal of solid state chemistry
© 2011 Elsevier Inc.