Structural, transport and spectroscopic properties of Ti4+ substituted magnetite: Fe3−xTixO4

The effect of Ti4+ ion on the formation of magnetite, which were prepared by solid-state route reaction method, were studied by resistivity, Raman and 57Fe Mössbauer spectrometry. Resistivity measured in the range of 10 < T < 300 K for Ti4+ magnetite Fe3−xTixO4 exhibit first order phase transformations at the Verwey transition Tv for Fe3O4, Fe2.98Ti0.02O4 and Fe2.97Ti0.03O4 at 123 K, 121 K and 118 K, respectively. No first order phase transition was observed for Fe2.9Ti0.1O4 and small polaron model retraces the semiconducting resistivity behavior with activation energy of about 72 meV. The changes in Raman spectra as a function of doping show that the changes are gradual for samples with higher Ti doping. The Raman active mode for Fe2.9Ti0.1O4 at ≅634.4 cm−1 is shifted as compared to parent Fe3O4 at ≅670 cm−1, inferring that Mn2+ ions are located mostly on the octahedral sites. 57Fe Mössbauer spectroscopy probes the site preference of the substitutions and their effect on the hyperfine magnetic fields confirms that Ti4+ ions are located mostly on the octahedral sites of the Fe3−xTixO4 spinel structure.

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► XRD shows that Fe3−xTixO4 (0.0 ≤ x ≤ 0.1) has cubic inverse spinel structure.
► The Tv for Fe3O4, Fe2.98Ti0.02O4 and Fe2.97Ti0.03O4 is at 123 K, 121 K and 118 K.
► The A1g Raman active mode for Fe3O4 (Fe2.9Ti0.1O4) is at about 669.7 (634.4) cm−1.
► Ti doping at Fe site leads to gradual changes in phonon modes.
► Mössbauer spectroscopy shows that Ti4+ ions are located on the octahedral sites.