engleski

Utilisation of ceramic thin-films for sensing humidity at room temperature

For semiconducting oxides, recent advantages that allowed conducting synthesis to yield materials with the constituent domains in the nano-range, proved beneficial in terms both of greater surface and pore exposure. Among such nanomaterials, materials used for sensing attracted much attention. In this research we derived nanosized ceria powders by a simple hydrothermal method, prepared intermediate slurries and then tape casted them onto conducting glass substrates, to derive planar thin-films with range of thicknesses. The thin-films were thoroughly characterized: structurally (powder and grazing incidence X-ray diffraction), morphologically (scanning electron microscopy and atomic force microscopy) and electrically (solid state impedance spectroscopy) in a wide range of temperature, frequency and humidity. Depth profiling points to monophasic crystalline ceria in form of slightly agglomerated spherical particles and low-roughness thin-films. Interestingly, the electrical measurements were performed employing surface geometry and cross-section geometry. From the dielectric spectroscopy results we elucidated the influence of the composition and film thickness on the electrical properties and derivatively the humidity sensing performance of the samples. Overall the relative humidity increase lead to a shift to higher conductivity, with gradual relaxation of the films. Thus proving the sensitivity and reversibility of the ceria thin films as humidity sensors.

ceria ; thin-films ; humidity sensing

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