Effect of composition and temperature on conductive and sensing properties of CeO2 + In2O3 nanocomposite films

The sensory response of nanostructured In2O3 + CeO2 composite films to hydrogen and carbon monoxide in air ambience is investigated for varying film composition and temperature ranging from 280 degrees C to 520 degrees C. The temperature dependence of the sensor responses S(S = R-0/R, where R-0 and R are respectively the film resistance in pure air and air containing the sample gas), exhibits the trend typical of such sensors, specifically, curves with maximum S-max at a certain temperature T-max. The values of Smax, characterizing the sensor response of the films significantly increase when a small amount of CeO2 is added to In2O3. Addition of CeO2 to In2O3 also results in a decrease in T-max. The measured XPS spectra show that at low CeO2 composition, the composite film structure is characterized by clusters with a high concentration of oxygen vacancies, which increase the chemisorption of reagents and oxygen. The maximum sensor response is observed in In2O3 + CeO2 composite films containing 3-10 wt.% CeO2. Further enrichment of the composite with CeO2 produces a sharp decrease in sensor response, which at 40 wt.% CeO2 is less than the response of pure In2O3. The response mechanism in the In2O3 + CeO2 composite is also investigated, considering the promotion of sensory reactions by small CeO2 nanoclusters located on the surface of the In2O3 nanocrystals. (C) 2014 Elsevier B.V. All rights reserved