Humidity sensing properties of NiO/Al2O3 nanocomposite materials

Humidity sensing properties measured by impedance spectroscopy (IS) and DC conductivity for a group of high surface area nanostructured 5–30% w/w NiO/Al2O3 composite materials are reported. The nanocomposites were prepared via a sol–gel method, which involved mixing of the respective sol–gel precursors and the subsequent drying and calcination at 873 K for 3 h. Accordingly, nanosized NiO particles dispersed in γ-Al2O3 matrix were formed. Conductivity changes amount to six orders of magnitudes were observed in response to 5–90% relative humidity (RH) change in the measuring chamber. Results indicate that humidity sensing was increased with the increase of NiO content in the composite. Moreover, conductance kinetics and conduction mechanism are discussed in terms of surface texture and nanostructured morphology of the composite materials that facilitate ionic transport mechanism.