Micro-Raman investigation of iron oxide films and powders produced by sol-gel syntheses

Films and powders of iron oxide (Fe2O3) prepared by two different sol–gel syntheses, starting from Fe(NO3)3·9H2O or FeCl3·6H2O, were investigated by Raman microscopy. Different phases with different morphology were produced according to the preparation. The spectra obtained in the micro‐Raman configuration were compared with the ambiguous data in the literature given by conventional Raman techniques. The principal difficulty in the correct interpretation of the Raman spectrum of the iron oxides is the co‐existence of different phases. Contradictory results are also explained by laser–induced thermal effects which easily change the wavenumbers and lineshapes of the phonons. A Stokes–Anti‐Stokes procedure was utilized to control the local temperature during the measurement and also for calibration of the wavenumbers. The micro‐Raman spectra of hematite, magnetite and other iron oxides are presented and compared with literature data. Copyright © 1999 John Wiley & Sons, Ltd.