CO and C₃H₈ sensing performance of coatings obtained from TiO₂-powders

Different semiconductor oxides have been widely studied for gas sensing applications. In this work, titanium dioxide (TiO₂) powders, synthesized by the homogeneous precipitation method, have been used to deposit thick coatings over sodalime glass sustrates by using a simple and scalable chemical method, Doctor Blade. TiO₂ powders were processed via the precipitation process from both titanium isopropoxide (TTI) and titanium butoxide (TiBu), separately, as Ti precursors. For processing the TiO₂, the precursors were dissolved in a mix of methanol, glacial acetic acid, and sulfuric acid; the disolution was stirried and heated at 65 °C and kept under a reflux system, resulting in a white precipitate. This precipitate was centrifuged, decanted, dried at 200 °C for 2 h, and finally calcined in air at 650 °C for 6 h. For depositing the TiO₂ coatings, a paste prepared from TiO₂ powders, deionized water and lactic was used. Afterwards, the coatings were dried at 45 °C for 2 h, and finally thermally treated at 400 and 450 °C for 3 h. The structure and morphology of the TiO₂ powders were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively, whereas the TiO₂ coatings were characterized by profilometry and Atomic Force Microscopy (AFM). The gas sensing response of the coatings was tested in both, C₃H₈ and CO, at different operating temperatures and gas concentrations. The sensitivity results were significant to both gases, and it was confirmed the potential application of TiO₂ coatings deposited by the Doctor Blade method as gas sensors.