Sensor performance of nanostructured TiO2-Cr2O3 thin films derived by a particulate Sol-Gel route with various Cr:Ti molar ratios

M. R. Mohammadi (Lead / Corresponding author), D. J. Fray

    Research output: Contribution to journalArticle

    3 Citations (Scopus)

    Abstract

    Nanocrystalline and nanostructured TiO2-Cr2O3 thin films and powders were prepared by a facile and straightforward aqueous particulate sol-gel route at low temperature of 400°C. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range of 17.7 nm to 19.0 nm. Moreover, the sols were stable over 4 months, with constant zeta potential measured during this period. The effect of the Cr:Ti molar ratio on the crystallization behavior of the products was studied. X-ray diffraction (XRD) analysis revealed that the powders crystallized at low temperature of 400°C, containing anatase-TiO2, rutile-TiO2, and Cr2O3 phases, depending on the annealing temperature and Cr:Ti molar ratio. Furthermore, it was found that Cr2O3 retarded the anatase to rutile transformation up to 800°C. The activation energy of crystallite growth was calculated to be in the range of 1.3 kJ/mol to 2.9 kJ/mol. Transmission electron microscopy (TEM) imaging showed that one of the smallest crystallite sizes was obtained for TiO2-Cr2O3 binary mixed oxide, being 5 nm at 500°C. Field-emission scanning electron microscopy (FESEM) analysis revealed that the deposited thin films had nanostructured morphology with average grain size in the range of 20 nm to 40 nm at 500°C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of NO2 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-Cr2O3 sensors followed the power law{S = A[\mathrm{gas}]^{B}} S = A [ gas ] B (where S is the sensor response, the coefficients A and B are constants, and [gas] is the gas concentration) for two types of gas, exhibiting excellent capability for detection of low gas concentrations.

    Original languageEnglish
    Pages (from-to)3922-3932
    Number of pages11
    JournalJournal of Electronic Materials
    Volume43
    Issue number11
    Early online date22 Jul 2014
    DOIs
    Publication statusPublished - Nov 2014

    Keywords

    • aqueous particulate sol-gel
    • Cr:Ti molar ratio
    • gas sensor
    • nanocrystalline
    • TiO-CrO

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