D03-ordered Fe3Al magnetic nanopowders synthesized by low oxygen induction thermal plasma

Abstract

D03-ordered Fe3Al alloy with a large anomalous Nernst coefficient is considered as a promising candidate for a low-cost, flexible, and durable magneto-thermoelectric generator (MTG). To improve the thermoelectric performance of the more and more complex and smaller MTG modules, the incorporation of high-quality magnetic nanopowders (MNPs) is one solution. However, synthesizing fully chemically ordered MNPs without coalescence and/or oxidation with a conventional approach is challenging. In this study, we demonstrated, for the first time, D03-ordered (degree of ordering = 0.48) Fe3Al MNPs synthesized via a low oxygen thermal plasma process combined with appropriate post-annealing treatment. The resulting single crystalline MNPs are spherical in shape with a mean particle diameter of 116 ± 96 nm and exhibit a soft magnetic characteristic (saturation magnetization ≈ 112 emu/g; and coercivity ≈ 5 Oe at room temperature). The fundamental alloying mechanism during the thermal plasma process was investigated via numerical calculations, confirming that the alloying followed the route through the Fe-Al droplet. Our results will potentially aid the mass synthesis of chemical ordered MNPs for wearable energy harvesting and self-powered Internet of things applications.