Study on emission spectral lines of hematite and magnetite for purity's differentiation

Abstract

Iron oxides have been investigated by employing mostly Fourier-transform infrared spectroscopy (FTIR). However, absorption spectra sometimes are difficult to obtain in situ, where accessibility to the location is limited. In this paper, we propose using emission spectra to investigate the purity of hematite (α-Fe2O3) and magnetite (Fe3O4). We used an infrared beam (wavelength of 1064 nm) from a pulsed laser to obtain emission spectra of the α-Fe2O3 and Fe3O4 for two different purities (99.99% and 96%) ranging from visible to near-infrared regions. The average values of full width at half maximum (FWHM) for the 99.99% purity were found to be 0.15 nm and 0.17 nm for the hematite and the magnetite, respectively; the average values of FWHM for the 96% purity were found to be 0.19 nm and 0.23 nm for the hematite and the magnetite, respectively. In addition, it is found that lower purity iron oxides exhibited a higher amplitude in the broader emission spectrum when compared to the iron oxides with high purity under the same experimental conditions. Therefore, by observing the amplitude of the broader emission spectra, it is possible to differentiate qualitatively between hematite and magnetite purities; moreover, from the average value of the FWHM of the spectral lines, it is possible to evaluate percentage purity content of hematite and magnetite, which are useful for different mechanical and biomedical applications. FTIR measurements also confirmed that the purity of the oxides can be found by measuring the peaks' shifts. However, the proposed technique can be used in place of FTIR, where accessibility to the measurement's location becomes problematic.