Pd- and Ca-doped iron oxide for ethanol vapor sensing

Iron oxide thin films doped with Ca and Pd, prepared by a liquid-phase deposition method (LPD) from aqueous solution, have been investigated as potential ethanol gas sensors. SEM and XRD analyses were used to characterize Fe2O3 LPD films. Hematite (α-Fe2O3), having an average crystallite size in the range between 20 and 30 nm, was the only crystalline phase detected on all undoped and doped films. The electrical response towards ethanol (100-500 ppm) has been studied in the temperature range of 300-500 °C. Both Ca and Pd promoters have shown a positive effect on the sensitivity of Fe2O3 films at the lower temperature investigated, whereas at higher temperature the undoped Fe2O3 film has shown better performances. The sensing properties of undoped and doped Fe2O3 thin films towards different interfering gases like NO2, CO and NH3 have been also investigated, showing that the selectivity to ethanol benefits of the Ca addition.