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 s yntheses, starting from Fe(NO3)(3). 9H(2)O or FeCl3. 6H(2)O, were investiga ted by Raman microscopy. Different phases with different morphology were pr oduced according to the preparation, The spectra obtained in the micro-Rama n configuration were compared with the ambiguous data in the literature giv en by conventional Raman techniques. The principal difficulty in the correc t interpretation of the Raman spectrum of the iron oxides is the co-existen ce of different phases. Contradictory results are also explained by laser-i nduced thermal effects which easily change the wavenumbers and lineshapes o f the phonons, A Stokes-Anti Stokes procedure was utilized to control the l ocal temperature during the measurement and also for calibration of the wav enumbers. The micro-Raman spectra of hematite, magnetite and other iron oxi des are presented and compared with literature data. Copyright (C) 1999 Joh n Wiley & Sons, Ltd.