High-pressure sintering behavior of α″-Fe16N2 nanopowder

Abstract

α″-Fe16N2 nanopowder was sintered at high-pressure and low temperature in order to explore its feasibility as a bulk magnet. TEM observation confirmed that the nanopowder was densely consolidated by sintering at a pressure of 1.2 GPa and temperatures around 200 °C. Increasing the sintering temperature enhanced the densification, leading to a suppression of oxidization. However, XRD analysis revealed that sintering at 222 °C caused the decomposition α″ → α-Fe + ε-Fe3N, which reduced the saturated magnetization (Ms) and coercivity (Hc). Consequently, sintering at 190 °C produced a dense magnet that retained the Ms of the raw powder due to the avoidances of oxidization and decomposition. On the other hand, it was found that Hc degrades after sintering, which is believed to be due to magnetic interaction between the particles.