Nitrogen dioxide and volatile sulfide sensing properties of copper, zinc and nickel chromite

Polycrystalline powders of CuCr2O4, ZnCr2O4 and NiCr2O4 were prepared from the decomposition of metal nitrates with glycine, and their structures confirmed by X-ray diffraction. The three spinels were mixed with ethyl cellulose dissolved in a suitable solvent (80:20 toluene-ethanol) to form pastes which were applied to substrates and dried. The gas sensing properties of the resulting thick films were investigated with ppm levels of NO2, CH3SH and C2H5SH at 220 degrees C. It was found that the spinels can be used to detect the presence-of these gases. Further experiments showed that by substituting some of the A or B cations with Li and Mg, respectively, the gas sensing properties of the-spinels can be altered significantly.