Synthesis and properties of iridium-doped hematite (α-Fe2O3)

► Ir-doped hematites were prepared by heating Ir-doped goethites. ► Ir-doping in hematite led to an increase in unit cell and a decrease in crystallite size. ► Ir-doping significantly affected magnetic, infrared and UV–Vis properties of hematite. ► The Morin transition temperature increased with an increase in Ir-doping. ► Ir ions brought about changes in the size and shape of the formed hematite particles. The effect of the incorporation of Ir3+ ions on the properties of α-Fe2O3 formed by dehydroxylation of α-FeOOH was investigated using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), 57Fe Mössbauer, UV–Vis–NIR and FT-IR spectroscopies, SQUID magnetometer, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Pure and Ir-doped hematite samples were obtained by heating of pure and Ir-doped goethites (α-FeOOH) formed by precipitation from mixed Fe(III)–Ir(III) chloride solutions in a highly alkaline medium. The incorporation of Ir3+ ions into the α-Fe2O3 structure led to changes in unit-cell dimensions, crystallinity, particle size and shape, as well as changes in the magnetic, infrared and UV–Vis properties. An increase in the temperature of the Morin transition with an increase in Ir-doping was observed by Mössbauer spectroscopy and magnetic measurements.