LAUSR

Abstract The quaternary interstitial nitrides Nd2Fe14BNδ was synthesized through the gas-solid reaction of N2 gas and Nd2Fe14B powders. It was found that Nd2Fe14BNδ alloy maintains the tetragonal structure (space group P42/mnm) with an expansion of the unit cell. Structure analyses showed the nitrogen concentration (δ) is about 0.352(48) with the volume-expansion ratio (ΔV/V) of 0.6613% in the unit cell. Refinement of neutron diffraction data indicated that the N has a site occupation preference (8:3) for the 4e (0, 0, 0.0652) site over the 4f (0.1000, 0.1000, 0) site. The room temperature saturation magnetization and the magnetocrystalline anisotropy field of Nd2Fe14BNδ slightly decrease by about 6% and 5% as compared to the parent alloy, respectively. The Curie temperature of Nd2Fe14B compound increases from 312 °C to 331 °C after nitrogenation with such a subtle volume expansion, which provides a validation prediction that we may increase the volume-expansion ratio to improve Tc further. Therefore, Nd2Fe14BNδ, with better temperature stability could be obtained.