Titanium and iron oxides produced by sol–gel processing of [FeCl{Ti2(OPri)9}]: structural, spectroscopic and morphological features

The first structurally characterised titanium and iron isopropoxide, [FeCl{Ti2(OPri)9}] (1), has been used as a single-source precursor for TiO2/Fe2TiO5 composites prepared by the sol–gel route. Two distinct hydrolysis and condensation conditions were employed, followed by drying and thermal treatment up to 1000 °C. Product composition and oxide phase transitions were characterised by powder X-ray diffractometry and Raman, electron paramagnetic resonance, Mössbauer and Fourier-transformed infrared spectroscopies. A mixture of nanometric-size TiO2 (anatase, 3.6–5.8 nm) and amorphous iron(III) oxide was obtained up to 500 °C, while TiO2 (rutile), α-Fe2O3 (hematite) and Fe2TiO5 (pseudobrookite) were found at 700 °C. At 1000 °C, only rutile and pseudobrookite were observed. These results suggest that 1 behaves as a type III single-source precursor. Powders calcined at 1000 °C were analysed for surface morphology, microstructure and elemental composition by scanning electron microscopy/energy dispersive X-ray spectroscopy. Results suggest no phase segregation on a sub-micrometer level. Different morphologies were observed for the materials produced by the N2 route, and this could relate to early crystal growth in an oxygen-deficient environment.