Gas-sensing properties of p-type α-Fe2O3 polyhedral particles synthesized via a modified polyol method

Abstract

The gas sensing properties of polyhedral α-Fe₂O₃ particles were investigated. The polyhedral α-Fe₂O₃ particles were synthesized via a modified polyol method with the addition of an extra amount of NaBH₄ in ethylene glycol, and fabricated to a thick gas sensing film after calcination at 500 °C and 900 °C. The polyhedral α-Fe₂O₃ particles exhibited a p-type nature, which is a new result opposite to other results of recent reports of semiconductor gas sensors using α-Fe₂O₃. In particular, we suggest that the difference between structure and morphology of α-Fe₂O₃ particles can lead to p-type and n-type characterization. In addition, we suggested that Na ions from NaBH₄ were incorporated into α-Fe₂O₃ oxide. They are the cause of the generation of holes in α-Fe₂O₃ oxide that led to the p-type nature of α-Fe₂O₃ oxide. The measurement of the sensor response to hydrogen, carbon monoxide, toluene, propane and ethanol revealed that the sensor device synthesized using polyhedral α-Fe₂O₃ particles is sensitive to hydrocarbons and ethanol. Importantly, the sensor device using polyhedral α-Fe₂O₃ particles calcined at 900 °C was strongly sensitive to ethanol due to the porous structure of the α-Fe₂O₃ particles.