Thin-film sensing layers based on Fe2O3-In2O3 nanocomposites with different component ratio and structural features were synthesized by inorganic modification of sol gel method. The phase composition and morphology of the composites as a function of the synthesis conditions were studied by X-ray diffraction, transmission electron microscopy, electron diffraction, differential scanning calorimetry, electron paramagnetic resonance and infrared spectroscopy. The gas-sensing parameters the Fe2O3-In2O3 composites were correlated with their structure. The synthesis conditions resulting in the formation in the, Fe2O3-In(2)O(3)composites of metastable gamma-Fe2O3 phase, which is characterized by an enhanced activity in adsorption and catalysis as compared to alpha-Fe2O3 oxide, were revealed. An improved sensitivity of gamma-Fe2O3 based composites to different gases was shown. The chemical and structural compositions of Fe2O3-In2O3 thin-film sensing layers and operating temperatures optimal for the detection of O-3, NO2 and C2H5OH were proposed. (C) 2015 Elsevier B.V. All rights reserved.