Preparation and gas-sensing properties of NiFe2O4 semiconductor materials

The gas-sensing materials, NiFe2O4, were prepared by inverse titrating chemical co-precipitation. After calcinations at 350-700 °C for 1 h, respectively, p-type semiconductor gas-sensing materials with inverse spinel structure were obtained. Effects of the calcining temperature on the phase constituents and microstructure were studied and characterized by simultaneous differential scanning calorimetry and thermogravimetry analysis (DSC-TGA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). NiFe2O4 used as sensitive materials of indirect heating structure sensors were fabricated on an alumna tube with Au electrodes and platinum wires. The gas-sensing properties were determined for using reducing gases. The results demonstrated that the sensors based on NiFe2O4 had good sensitivity and good selectivity to toluene. The difference in response for various tested gases might be attributed to absorption of reducing gases and reaction between these gases and the absorbed oxygen.