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Thick film technique is popular because of low cost, simple for construction and better sensing surface area, hence for resistive gas sensor thick films of pure ZrO2 powder were prepared by Standard screen printing technique. The material was characterized by X-Ray diffraction pattern, surface morphology was observed by SEM, elemental composition were observed by EDAX and optical properties were studied with UV spectroscopy Techniques, electrical properties were studying with different applied voltages and at different working temperature. X-Ray Diffraction studies confirmed that the combinations of tetragonal and monoclinic structure. The energy band gap and the thicknesses of the films were evaluated, the crystalline grain size was determined using Scherrer's formula. The gas sensing performances of various gases were tested with working temperatures from 100oto500oc. The sensitivity and selectivity to different gases was tested and the resistive thick films showed highest response to NH3 (100 ppm) at 300°C. It was observed that increase in gas concentration its sensing response goes on increasing but slowly increase being still constant for higher concentration. The sensitivity and selectivity may be further enhanced by doping other element and ZrO2 can be stabilize by mixing other oxides. The quick response and fast recovery time was recorded. [ABSTRACT FROM AUTHOR]

Thick films of AR Grade nano Fe2O3 material with n-type semiconducting properties were prepared and tested for their gas sensing performances. Thick films of the materials were prepared by screen printing technique. The gas sensing performance was studied using static gas sensing system. The material was tested for various gases such as CO, CO2, NH3, Cl2, H2, LPG, ethanol and H2S. The nano Fe2O3 film showed maximum sensitivity to ethanol gas at 350 °C temperature at 250 ppm concentration with short response time and large recovery time. Physical and structural properties of the film material were studied by SEM, TEM, XRD and UV spectroscopy. [ABSTRACT FROM AUTHOR]

Strontium titanate (SrTiO3) nanopowder has been synthesized through a sol-gel-hydrothermal method. The X-ray diffraction studies of SrTiO3 nanopowder have shown that the as-prepared powder was single phase, crystalline, and has a cubic perovskite structure (ABO3) with a lattice constant a = 3.903 Å. The particle size calculated from FWHM was ∼22 nm. SrTiO3 nanopowder was examined using thermo gravimetric analysis; differential thermal analysis and UV-visible absorption spectroscopy. The transmission electron microscopic investigations have shown that the particle size of the as-prepared powder has a mean size of 34 nm. Then highly sensitive and selective sensors to H2S based on glass substrate were fabricated successfully by screen-printing technique. Sensitivity, selectivity, response time, and recovery time of the sensors were systematically investigated as a function of operating temperature, using H2S, CO, CO2, H2, Cl2, LPG, C2H2OH, O2, NH3 and NO2 as test gases. The sensitivity was found to lie below and around the ppm level for H2S gas at 150 °C. [ABSTRACT FROM AUTHOR]

Thick films of AR grade In2O3 were prepared by standard screen-printing technique. The gas sensing performances of thick films were tested for various gases. It showed maximum sensitivity to ethanol vapour at 350°C for 80 ppm concentration. To improve the sensitivity and selectivity of the film towards a particular gas, In2O3 sensors were surface-modified by dipping them in a solution of 2% nanosilver for different intervals of time. Obtained results indicated that spherical nano-Ag grains are highly dispersed on the surface of In2O3sensor. The surface area of the nano-Ag/ In2O3 sensor is several times larger than that of pure In2O3 sensor. In comparison with pure In2O3 sensor, all of the nano-Ag-doped sensors showed better sensing performance in respect of response, selectivity, and optimum operating temperature. The surface-modified (30 min) In2O3 sensor showed larger sensitivity to H2S gas (10 ppm) at 100°C. Nano silver on the surface of the film shifts the reactivity of film from ethanol vapour to H2S gas. A systematic study of gas sensing performance of the sensor indicates the key role played by the nano silver species on the surface. The sensitivity, selectivity, response, and recovery time of the sensor were measured and presented. [ABSTRACT FROM AUTHOR]