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The preparation of γ-Fe2O3by the thermal decomposition of Fe3O4obtained from the hydrazine reduction of ferric nitrate was studied employing differential thermal analysis (DTA), and X-ray diffraction (XRD). Here we report a simple technique that does not need any explosive or high-energy reactions to obtain γ-Fe2O3. The ethanol sensitivity of pure and Pt doped γ-Fe2O3were investigated by studying the electrical resistance characteristics of sensor elements prepared from this material. The Pt doped sensor elements showed a linear response of sensitivity, in the range of 1–1000 ppm ethanol in air, in the logarithmic scale. γ-Fe2O3behaves as an n-type basic semiconducting oxide when exposed to ethanol vapors and in turn ethanol probably decomposes via the route of CH3CHO to form CO2and H2O. The maximum sensitivity after Pt incorporation is found at 175°C. The high sensitivity of the sensor to ethanol can be explained on the basis of a catalytic activity that invokes the acid base properties of the test gas and the sensor surface. The response time of the elements to 10 ppm ethanol in air is less than 30 s. Cross sensitivity to other gases like liquefied petroleum gas (LPG), CO, CH4, H2, H2S and NH3was also studied.

Barium stannate, a semiconducting oxide with cubic perovskite structure, has been prepared by the thermal decomposition method. Of its several applications, this material has proved to be one of the successful candidates for chemical sensors to detect toxic and inflammable gases. BaSnO3was incorporated with different noble metal additives and the gas sensing behavior of these materials to various reducing gases like LPG, CO and CH4have been studied. A model for the electronic interaction between additives and semiconducting BaSnO3gas sensors is discussed. The model is based on the depletion layer that is created due to metal-semiconducting oxide contact. Change of the gas sensor characteristics before and after the exposure to the different test gases has been explained on the basis of work function of metal additives. The valence band X-ray photoelectron spectroscopy studies were used to support the results on the gas sensing characteristics in each of the noble metal incorporated BaSnO3sensor materials and bring out the difference in the sensing mechanisms in these materials.