Abstract

Nanostructured TiO2-CeO2 thin films and powders were prepared by a straightforward aqueous particulate sol-gel route Titanium (IV) isopropoxide and cerium chloride were used as precursors and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area The effect of Ce Ti molar ratio was studied on the crystallisation behaviour of the products X-ray diffraction (XRD) and Fourier transform Infrared spectroscopy (FTIR) revealed that the powders crystallised at the low temperature of 500 degrees C containing anatase-TiO2 rutile-TiO2 and cubic-CeO2 phases as well as Ti8O15 Ti3O5 and Ce11O20 depending on annealing temperature and Ce Ti molar ratio Furthermore it was found that CeO2 retarded the anatase to ruffle transformation up to 700 C The activation energy of crystallite growth was calculated in the range 1 92-8 79 kJ/mol Transmission electron microscope (TEM) image showed that one of the smallest crystallite sizes was obtained for TIO2-CeO2 binary mixed oxide being 3 nm at 500 C Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had nanostructured morphology with the average grain size in the range 17-28 nm at 500 C Thin films produced under optimised conditions showed excellent microstructural properties for gas sensing applications They exhibited a remarkable response towards low concentrations of CO gas at low operating temperature of 200 C resulting in increased thermal stability of sensing films as well as a decrease in their power consumption Furthermore calibration curves revealed that TiO2-CeO2 sensors follow the power law S = A[gas](B) (where S is sensor response coefficients A and B are constants and [gas] is the gas concentration) for the two types of gases and they have excellent capability for the detection of low gas concentrations (C) 2010 Elsevier B V All rights reserved