Gas sensing with semiconducting perovskite oxide LaFeO3

This paper reports results of gas-sensing studies with antiferromagnetic perovskite oxide LaFeO3 thick films, for a possible use of the films in semiconductor gas sensors for monitoring pollutant, toxic and flammable gases in atmospheric air. Conductance responses of the nanocrystalline LaFeO3 thick films with both Au and Pt electrodes were measured at exposure of the films to CO, CH4 and NO2 at different concentrations in air and also at different temperatures. Different temperatures can be used to make the films sensitive to different gases. This gives a possibility to use an array of films for a selective detection in the case of a gas mixture. The sensitivity of the films was found to be high and it was possible to detect, e.g., CO and CH4 concentrations down to a few tens of ppm, and NO and NO2 concentrations already in the sub-ppm region. An array of two sensing films, operating at 270 deg. C and 420 deg. C, respectively, was used to monitor different mixtures of CO and CH4. The results point to a possibility to use semiconductor gas sensors based on LaFeO3 thick films for monitoring, e.g., flammable gases in coal mines