The Strong Effect of Fe on the Structural and Optical Properties of CdTiO3

Fe-doped Cadmium titanium oxide (CdTiO3) powders were prepared by the sol-gel method. The samples were characterised by Fourier-transform infrared (FTIR) spectroscopy, Electron paramagnetic resonance (EPR) technique, x-ray diffraction (XRD) and diffuse reflection spectroscopy (DRS). The X-ray diffraction results show well that all the samples displayed the ilmenite structure with the presence of minor traces of Titanium Dioxide (TiO2) and (Cadmium oxide) CdO phases, which ratio was shown to change with various concentrations in Fe. The estimated average particle size of the samples was around 56 nm. The photoluminescence properties of Fe-doped CdTiO3 were investigated. FTIR spectroscopy showed the presence of the Ti-O and CdO vibration bands. The spectra from the diffuse reflectance spectroscopy (DRS) DRS showed a red shift and a strong reduction of the gap energy compared to that of the pure sample (CdTiO3). The crystal structure of the CdTiO3 nano-powder presented a certain level of distortion due to the high concentration of oxygen vacancies. In fact, under (400) nm excitation, a clear green emission consecutive to oxygen vacancies was observed. The luminescence spectra of the Fe- doped CdTiO3 samples revealed that, due to oxygen vacancies, the emission and absorption intensities were both enhanced when the size was decreased. It can be inferred from our studies that the concentration of oxygen vacancies could be increased by reducing the crystallite size. The optical and ESR studies showed that the form of bivalent and trivalent states of iron were observed in distorted octahedral symmetry.