Abstract
Humidity sensing properties measured by impedance spectroscopy (IS) and DC conductivity for a group of high surface area nanostructured 5–30% w/w NiO/Al
2O
3 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-Al
2O
3 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.