Synthesis, morphology, microstructure and magnetic properties of hematite submicron particles

We report on hydrothermal synthesis, plate-like morphology, microstructure and magnetic properties of hematite (α-Fe2O3) plate-like particles. The sample is obtained immediately after the hydrothermal process without using any template and without further heat treatment. The so-obtained sample is characterized by X-ray powder diffraction (XRPD), energy-dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and superconducting quantum interference device (SQUID) magnetometer. XRPD confirms the formation of a single-phase hematite sample whereas EDX reveals that iron and oxygen are the only components of the sample. SEM, FE-SEM, TEM and HRTEM show that the sample is composed of plate-like particles. The width of the particles is ∼500 nm whereas thickness is ∼100 nm (aspect ratio 5:1). The HRTEM images exhibit well defined lattice fringes of α-Fe2O3 particles that confirm their high crystallinity. Moreover, the HRTEM analysis indicates the plate-like particles preferring crystal growth along [0 1 2] direction. Magnetic measurements display significant hysteretic behavior at room temperature with coercivity HC = 1140 Oe, remanent magnetization Mr = 0.125 emu/g and saturation magnetization MS = 2.15 emu/g as well as the Morin transition at TM ∼ 250 K. The magnetic properties are discussed with respect to morphology and microstructure of the particles. The results and comparison with urchin-like, rods, spherical, hexagonal, star-like, dendrites, platelets, irregular, nanoplatelets, nanocolumns and nanospheres hematites reveal that the plate-like particles possess good magnetic properties. One may conjecture that the shape anisotropy plays an important role in the magnetic properties of the sample.

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► Plate-like hematite α-Fe2O3 particles were prepared by template-free hydrothermal route.
► The micrographs show a width of the plate-like particles of ∼500 nm and a thickness of ∼100 nm (aspect ratio ∼ 5).
► The HRTEM shows perfect lattice fringes and preferring crystal growth along [0 1 2] direction.
► The values of the coercivity, remanent magnetization and saturation magnetization at room temperature are HC = 1140 Oe, Mr = 0.125 emu/g and MS = 2.15 emu/g, respectively.
► The Morin temperature is observed at TM ≈ 250 K.