A comparison of NO2 sensing characteristics of α- and γ-iron oxide-based solid-state gas sensors

Abstract

In this work, we report on the successful synthesis of α- and γ-iron oxide (hematite and maghemite, respectively) nanopowders using a simple sol–gel technique followed by dries in supercritical ethanol. Microstructural and morphological characterizations were performed using X-ray diffraction (XRD) and transmission and scanning electron microscopies (TEM and SEM). The iron oxide semiconducting materials have been tested as sensing layer in solid-state conductometric planar sensors for the monitoring sof low NO2 concentrations in air. This study demonstrated that the crystalline microstructure of the iron oxide nanopowders greatly affects the NO2 sensing properties, allowing to tune the performances of the developed sensor towards the target gas. γ-Fe2O3 nanopowder-based sensor resulted to have better performance than α-Fe2O3 sensor for NO2 monitoring.