Influence of synthesis route on structural, optical, and electrical properties of TiO2

TiO2 samples with two different morphology were synthesized via sol-gel and hydrothermal techniques. The effect of synthesis procedure on structural, morphological, optical, and electrical properties was studied. Rietveld analysis revealed that anatase phase having tetragonal structure dominates at room temperature. The presence of anatse phase of TiO2 was further confirmed by the analysis of various peaks obtained from the Raman spectra. The field-emission scanning electron microscopy (FESEM) and transmission electron microscopy micrographs depicted the formation of two different kinds of morphologies with average particle size ranging from 9.87 to 11.35 nm. The FESEM micrographs showed homogeneous particle distribution for sol-gel synthesized sample, whereas it depicted rod-like structure in the sample synthesized via hydrothermal technique. The X-ray photoelectron spectroscopy analysis clearly indicated the presence of appropriate chemical composition and valency states of Ti and O element in TiO2 samples. The optical bandgap was estimated from the UV-visible spectra and found to be in corroboration with the reported values. The conductivity spectra were analyzed using Jonscher power law. The values of activation energy suggested that the conduction mechanism is thermally activated. The conductivity isotherms were scaled through Ghosh scaling model. In the sol-gel synthesized sample, the conduction mechanism was found to be independent of temperature in the entire measured temperature range; however, the hydrothermally synthesized sample depicted that the conduction mechanism is temperature-dependent in the measured temperature range. This discrepancy was understood in terms of structural changes and charge trapping within the structure.