Nanostructured oxides by high-energy ball milling technique: Application as gas sensing materials

It is commonly believed that the gas sensitivity can be improved with the use of nanosized materials for the sensing layer. In this paper, we present several types of nanosized metal oxide semiconductor materials that have been successfully synthesized for the sensing of both ethanol and oxygen gases. Using the high-energy ball milling process, stable nanoparticle powders down to a few nanometers can be obtained at room temperature. For ethanol gas sensing application, nanosized α-Fe₂O₃-based solid solutions mixed separately with different mole percents of SnO₂, ZrO₂ and TiO₂ are synthesized and fabricated into thick film sensor devices. In the case of oxygen sensing application, stabilized zirconia-based and TiO₂-based solid solutions mixed with different mole percents of α-Fe₂O₃ are synthesized as the sensing materials. All the nanosized oxide materials are systematically characterized using XRD, and the fabricated sensor devices are characterized for their electrical and sensing properties. The sensing properties are compared and analyzed and the electrochemical reaction mechanisms are explained for the different types of sensing materials. The effects of the nanosize on the sensing properties are investigated. In the case of ethanol sensing, the α-Fe₂O₃-SnO₂ and α-Fe ₂O₃-ZrO₂ materials are found to be most suitable whereas for the oxygen sensing, the ZrO₂-α-Fe ₂O₃ type is useful for low temperature application.