Influence of particle size on H2 and H2S sensing characteristics of nanocrystalline nickel ferrite

Nanocrystalline nickel ferrite (NiFe2O4) was synthesized by sol-gel self-combustion technique. Ball milling at room temperature was carried out to control the particle size. Characterization of synthesized powders was made using X-ray diffraction (XRD) and Transmission electron microscopy (TEM) analysis. Fine powder resulted from milling was used to prepare gas sensing elements in pellet form. The gas-sensing properties were studied in presence of hydrogen and hydrogen sulfide as test gases. The gas-response was found to be strongly influenced by the particle size. Significantly high sensitivity of ~75% was found for ~5.35 nm nickel ferrite in presence of 200 ppm H2S at an operating temperature of 150 °C. Sensitivity was found to increase with temperature before being maximum at a particular operating temperature.