Study of phase transformation in iron oxides using Laser Induced Breakdown Spectroscopy

Synthetic magnetite (Fe3O4) was heated in air at 200–500 °C for different time periods to study its phase transformation to maghemite (γ-Fe2O3) and hematite (α-Fe2O3). Laser Induced Breakdown Spectroscopy (LIBS) was used to take the spectra of these samples which were then compared to the spectra of standard iron oxide powders using linear correlation. The linear correlation procedure used showed probabilities of identification close to unity. Complementary techniques to LIBS, Fourier Transform Infrared (FTIR) spectroscopy and X-ray Diffraction (XRD) analysis were also used to characterize iron oxides. By taking advantage of the time gated detector capability of LIBS, the identification of iron oxide phases was found to be in good agreement with FTIR and XRD analysis. This study demonstrates that LIBS can be successfully applied to the characterization of the oxidation states of multivalent oxides of elements like Fe, Cr, Pb, and others.