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Barium strontium titanate ((Ba0.87Sr0.13)TiO3-BST) ceramic powder was prepared by mechanochemical process. The thick films of different thicknesses of BST were prepared by screen-printing technique and gas-sensing performance of these films was tested for various gases. The films showed highest response and selectivity to ammonia gas. The effect of film thickness on gas response was also studied. As prepared BST thick films were surface modified by dipping them into an aqueous solution of titanium chloride (TiCl3) for different intervals of time. Surface modification shifted response to H2S gas suppressing the responses to ammonia and other gases. The surface modification, using dipping process, altered the adsorbate-adsorbent interactions, which gave the unusual sensitivity and selectivity effect. Sensitivity, selectivity, thermal stability, response and recovery time of the sensor were measured and presented. [ABSTRACT FROM AUTHOR]

H2S gas sensing properties of BST ((Ba0.67Sr0.33)TiO3) thick films are reported here for the first time. BST ceramic powder was prepared by mechanochemical process. Thick films of BST were prepared by screen-printing technique. The sensing performance of the films was tested for various gases. The films were surface customized by dipping them into aqueous solutions of CuCl2 and CrO3 for various intervals of time. These surface modified BST films showed improved sensitivity to H2S gas (100 ppm) than pure BST film. Chromium oxide was observed to be a better activator than copper oxide in H2S gas sensing. The effect of microstructure and amount of activators on H2S gas sensing were discussed. The sensitivity, selectivity, stability, response and recovery time of the sensor were measured and presented. [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]