Properties of α-Fe2O3 (hematite) nanoparticles can be significantly modified by substitution of Fe3+ ions with other metal ions. Due to the same charge and similar radii, Ru3+ ions are potentially suitable for the substitution of Fe3+ ions in α-Fe2O3. In the present work, the effects of Ru3+ ions on the structural, magnetic and optical properties of α-Fe2O3 nanorods prepared by hydrothermal precipitation and calcination were investigated. Ru-doped α-FeOOH (goethite) nanorods were formed by hydrothermal precipitation in a highly alkaline medium in the presence of up to 2 mol% of Ru3+ ions, while in the presence of 3 to 5 mol% of Ru3+ ions cylinder-shaped α-Fe2O3 particles, containing self-assembled and fused nanoparticles, were formed. Pure and Ru-doped α-Fe2O3 nanorods were prepared by calcination of precipitated pure and Ru-doped α-FeOOH nanorods at 500 °C. A gradual elongation of α-Fe2O3 nanorods with increased Ru doping to highly elongated Ru-doped α-Fe2O3 nanoneedles at 2 mol% Ru (Fig. 1a) was observed. The influence of the molar fraction of Ru3+ ions on the magnetic properties of Ru-doped α-Fe2O3 was investigated using magnetic measurements (Fig. 1b) and 57Fe Mössbauer spectroscopy (Fig. 1c). Temperature of the Morin transition gradually rose above room temperature with increasing Ru3+-for-Fe3+ substitution in α-Fe2O3. The optical band gap in Ru-doped α-Fe2O3 nanorods was found to get gradually narrower with increased Ru doping.

Influence of Ru doping on the structural, magnetic and optical properties of α-Fe2O3 nanorods

ACS Fall 2021

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