Reducing gas-sensing properties of ferrite compounds MFe2O4 (M=Cu, Zn, Cd and Mg)

Four kinds of ferrites, MFe2O4 (M=Cu, Zn, Cd and Mg), having high specific surface area (40–80 m2/g) were prepared by a coprecipitation method and tested for sensing properties to reducing gases of CO, H2, LPG, C2H5OH and C2H2. The gas sensitivity depended considerably on the kinds of ferrites and the gases to be detected. All of the ferrites were more sensitive to C2H2, C2H5OH or LPG than to H2 or CO. Among the ferrites, the gas sensitivity tended to decrease in the order MgFe2O4∼CdFe2O4>CuFe2O4>ZnFe2O4, which was in fact coincident with the increasing (or decreasing) order in specific surface area (or grain size). It was revealed that MgFe2O4 and CdFe2O4 were the most sensitive and selective to LPG and C2H2, respectively, among the ferrites tested.