Change of ferric oxide (Fe2O3) semiconductor conductivity type in the interaction with reducing gases

The interaction processes between semiconductor ferric oxide (α-Fe2O3) obtained by different methods and reducing gases are investigated. It is shown that only α-Fe2O3 doped by 1 wt.% ZnO changes its conductivity type from p to n when adsorbing such gases. The long-term stability of a semiconductor gas sensor made of undoped α-Fe2O3 and α-Fe2O3 doped by SO42−, Zn2+ and Sn4+ ions is studied. The most stable is the α-Fe2O3 + 20% SnO2 reducing gas sensor. Its conductivity changes less than 5% per month. These properties of α-Fe2O3 are associated with the Mössbauer spectra of the materials under investigation. A new type of semiconductor gas-sensing device based on a gas-controlled p-n junction is suggested.