Synthesis and characterization of xTiO2(1 − x)α-Fe2O3 magnetic ceramic nanostructure system

Rutile-doped hematite xTiO2(1 − x)α-Fe2O3 (x = 0.0–1.0) nanostructures were synthesized using mechanochemical activation by ball milling. Their complex structural, magnetic and thermal properties were characterized by X-ray diffraction, Mössbauer spectroscopy and simultaneous DSC–TGA. XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time. For the molar concentrations x = 0.1 and 0.3, the Mössbauer spectra were fitted with one, two, three or four sextets, corresponding to the degree of Ti ion substitution of Fe ions in hematite lattice. After 12 h of ball milling, the completion of Ti ion substitution of Fe ions in hematite lattice occurs for x = 0.1 and 0.3. For x = 0.5 and 0.7, Mössbauer spectra fitting required sextets and a quadrupole-split doublet, representing Fe ions substituting Ti ions in the rutile lattice. The completion of Fe ion substitution of Ti ions in rutile lattice was not observed, as indicated by XRD patterns and Mössbauer spectra for these two molar concentrations. Simultaneous DSC–TGA measurements revealed that the mechanochemical activation by ball milling has a strong effect on the thermal behavior of this nanostructure system. The enthalpy dropped dramatically after 2 h of milling time, indicating the strong solid–solid interactions between TiO2 and α-Fe2O3 after ball milling. The change in weight loss of hematite was caused by the decrease of grain size and ion substitutions between Fe and Ti after mechanochemical activation.