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In this work we report the synthesis, microstructure, electric properties and sensing performance of BaSnO3 (BS) powder, it was prepared by mechano-chemical method. As prepared powder is calcinated at temperatures 1100°C, and 1300°C tested for crystallization. Thick films were prepared using simple screen-printing technology. Structural and electrical analyses were performed and the results have been correlated. The material was tested for various gases such as CO, CO2, NH3, Cl2, H2, LPG, ethanol, and H3S. The pure BS film shows good response multiple gases at various operating temperature up to 500°C as NH3, CO2, CO, ethanol and, H3S for different gas concentrations, when the pure film is surface modified with aqueous solution of Cucl2 using simple dipping technique for various time intervals (5 min., 10 min., 20 min. and, 30 min.), film improves the selectivity and sensitivity. Maximum response (S=36.2) was found to H2S gas at temperature of 250°C and S=12.1 for ethanol at 500°C for gas concentration of 50 ppm with film dipped for 10 min. time interval. The characterization of the films was done by XRD, SEM and TG-DTA. Crystallite size, texture coefficient, specific surface area, electric properties and gas sensitivity of the films were measured and presented. [ABSTRACT FROM AUTHOR]

MoO3 thin films have been prepared by a simple spray pyrolysis technique at substrate temperature 250°C. The structure and morphology of thin films are characterized by X-ray powder diffraction (XRD), scanning electron microscopy and UV-vis spectroscopy. The gas sensing properties of MoO3 thin film is studied at gas concentration 400 ppm and working temperature of 100-400 °C. It was found that the sensitivity depended on the working temperatures and also H2S gas concentration. The results show that the MoO3 thin film can be used to fabricate high performance H2S gas sensors. [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]

Tin oxide thin films were deposited on alumina substrates at 350°C by spray pyrolysis technique. The films were studied after annealing them in air at different temperatures 550°C, 750°C and 950°C for 30 min. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption spectroscopy technique. The grain size was observed to be increased, ranging from 40 to 56.1 nm, with the increase in annealing temperature. Absorbance spectra were taken to examine the optical properties. The band gap energy was observed to be decreased with the increase in annealing temperature. These films were tested to various gases at different operating temperature ranging from 50°C to 450°C. The Tin Oxide film showed maximum sensitivity to H2S gas. The H2S sensing property of the SnO2 films was investigated with different annealing temperatures of the films and at different concentrations of H2S gas. It was found that the annealing temperature of the film significantly affects the sensitivity of the SnO2 to the H2S gas. The maximum sensitivity was found in case of the film annealed at temperature 950°C at the operating temperature 100°C. The sensitivity was found to be increased by 24% in case of the film annealed at 950°C as compared to the sensitivity of the film annealed at 550°C. The observed response of the film was for gas concentration of 10 ppm for H2S with reasonable sensitivity. The quick response and fast recovery are the main features of this film. The effect of annealing temperature on the structural, microstructural, optical and gas sensing properties of the nanocrystalline tin oxide thin films were studied and discussed. [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]