Composite NiO/Al2O3 was prepared by calcination of Ni/Al hydrotalcite for gas sensing materials. Methods of XRD, SEM, TEM, EDS and BET were used to analyze the structure, composition and morphology of the composite oxide. It was found that the sample was composed of crystal NiO and amorphous Al2O3. Furthermore, the composite NiO/Al2O3 has smaller grain size and larger surface area than that of pure NiO obtained by the same process. In the gas sensing experiments, the sensor based on NiO/Al2O3 showed superior gas sensing response and selectivity to 2-chloroethanol at low temperature. The response (Rg/Ra) of NiO/Al2O3 was 6.8–20 ppm 2-chloroethanol at 160 °C. The role of Al2O3 in the composite was also discussed.

Semiconducting sensors offer an inexpensive and simple method for monitoring gases. Sensors based on the ABO3-type composite oxides materials have an advantage of high stability. The perovskite structures of these compounds are preserved, when an A-site deficiency of some perovskite structure compounds was formed. However, they exhibit particular physical properties. In this paper, La0.9□0.1FeO3 powder with an orthorhombic perovskite phase was prepared by sol-gel method. The electrical properties and CO-sensing characteristics of the La0.9□0.1FeO3 were also investigated. The results demonstrated that the La0.9□0.1FeO3 was a p-type semiconductor material. Compared with LaFeO3, the conductance of La0.9□0.1FeO3 was better than that of LaFeO3. The sensor based on La0.9□0.1FeO3 showed excellent CO gas-sensing characteristics.