Synthesis of submicron-sized acicular goethite and platelet-like hematite particles and dependence of magnetic properties of α-Fe particles on their shape and size

Acicular goethite and platelet-like hematite particles, ranging submicron to micron size, were synthesized by a newly developed hydrothermal synthesis route without using any organic additives or solvents. The acicular goethite and platelet-like hematite particles could be converted to α-Fe particles by a common hydrogen reduction without the need for any coating to prevent sintering. The α-Fe obtained in this study had lesser number of voids compared to those prepared by conventional methods using silica coating to prevent sintering. Both the acicular and platelet-like α-Fe particles exhibited high saturation magnetization around 190 emu/g. We also demonstrated differences in the coercivity of submicron α-Fe particles depending on their shape.