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

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 NO 2 concentrations in air. This study demonstrated that the crystalline microstructure of the iron oxide nanopowders greatly affects the NO 2 sensing properties, allowing to tune the performances of the developed sensor towards the target gas. γ-Fe 2 O 3 nanopowder-based sensor resulted to have better performance than α-Fe 2 O 3 sensor for NO 2 monitoring.