Hello,

I think that it is worth to start from the simplest way, i.e. examine the powder by XRD. Both diffractograms are similar, but in the case of Fe2O3 there are signals below 30 degrees (about 26 degrees for 220 and 211 peaks) not visible for the Fe3O4 phase and just after the peak 422 (about 53 degrees for Fe3O4) an additional peak or at least appears extension for the Fe2O3 phase (~54 degrees). For the quantitative analysis the composition of the intensity with the standard patterns should be performed (the standard curve method or the internal standard method).

Dear Nirmala Ilankoon,

I think the x ray diffraction is not a feasible technique for quantification of maghemite and magnetite in the mixtures. Both these phases have a close packing parameters with cubic unit cells. Mossbauer spectroscopy is the best alternate technique for the quantification of the same.

Regards

You can also try EELS to determine the Fe2+/Fe3+ ratio from the L3/L2 white line ratio. There are many studies on this, using different ways of background treatment which will influence the numerical robustness of the technique.

Dear Nirmala,

I will recommend bellow you some reviews or papers that could help you to find some answers at your questions.

However, I will like to point out for your consideration one key-aspect regarding instability of magnetite particles during storing in inadequate conditions. Please consider that magnetite (nano)particles are very sensitive to oxygen and might undergo oxidation to maghemite (γ-Fe2O3), whereas in the presence humidity/water could be converted to some hydroxides, such as Fe(OH)3.

You can consider for more information the following references (M. Yamaura et al. / Journal of Magnetism and Magnetic Materials 279 (2004) 210–217; R.Y. Hong et al., Magnetic field synthesis of Fe3O4 nanoparticles used as a precursor of ferrofluids, Journal of Magnetism and Magnetic Materials 310 (2007) 37–47, doi:10.1016/j.jmmm.2006.07.026).

Good luck in realization of your study and best regards,

Marius

For eventual interest:

Review, Wei Wu et al., Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications, Sci. Technol. Adv. Mater. 16 (2015) 023501 (43pp), doi:10.1088/1468-6996/16/2/023501

Review, Susheel Kalia et al., Magnetic polymer nanocomposites for environmental and biomedical applications, Colloid Polym Sci (2014) 292:2025–2052, DOI 10.1007/s00396-014-3357-y

Raman spectroscopy can readily give you information on the iron oxide phase. If you go for it, try using low laser power since magnetite can turn into hematite during measurements at even moderate laser power.

You can check this reference to identify the phase:

Article Raman spectroscopy of iron oxides and (oxy)hydroxides at low...

Thank you everyone for the answers and recommendations. very helpful!

I think you can use XRD, Mossbauer spectroscopy, and XPS techniques to get an accurate answer for your question.

Dear Nirmala,

I’m so sorry to see your question only now.

Nevertheless, I'll answer it once it is a challenge task.

The best way to qualitatively and quantitatively determine magnetite versus maghemite is by far using Mössbauer spectroscopy. You will be able to use XPS as well, however, less informative by the chemical environment than Mössbauer.

In such a case, you will have at once the full differentiation by the spectrum itself.

Magnetite will show you straight two superimposed spectra, one for Fe2+ and Fe3+ (octahedral) and another for Fe3+ (tetrahedral).

For maghemite, you will see just one, that may be fitted with two contributions (octahedral and tetrahedral), usually with larger width.

The hyperfine filed at room temperature is quite different; you may identify then straight. At low temperatures (N2) it is clearer about the difference. At lower temperatures (liquid helium) you may impose some extra difficulty due to magnetic behavior.

You will be able to perform a hyperfine field distribution that gives you a reasonable particle size distribution.

The quantification is direct by fitting to have in hands the Mössbauer parameters. Especially the Fe3/Fe2 relationship, that will, in fact, reflect to you by the value of the hyperfine field, the isomer shift will give you one good idea of the chemical environment that your iron atoms are feeling, such as isomorphic substitutions, deviation of stoichiometry, very small particle sizes, leading to a super paramagnetic behavior.

In the literature you will find the Mössbauer parameters to differentiate them, I’ll not list them here, they are quite sensitive to the exact temperature of your experiment.

Good luck

WNM