Synthesis, Characterization of Nickel Ferrite and Its Uses as Humidity and LPG Sensors

Nanostructured nickel ferrites (sample B 1 and B 2 ) were synthesized by chemical precipitation method using two different precipitating agents; sodium and ammonium hydroxides. The samples were characterized by using powder X-ray diffraction, scanning and transmission electron microscopy techniques. The X-ray diffraction revealed the formation of nickel ferrite with lattice parameter a = 8.3 Å and the average crystallite sizes of the samples B 1 and B 2 were 50 and 15 nm respectively. Surface morphology of the sample B 2 exhibited the higher number of adsorption sites in comparison to B 1 . Transmissions electron microscopy observations confirmed the formation of nanostructured nickel ferrite. Further the pellets, thick and thin films of materials B 1 and B 2 were prepared and investigated with the exposition of humidity and LPG. Maximum average sensitivity for humidity was formed as 53.74 MΩ/%RH. Also the maximum value of sensitivity was found 62.3 for 4 vol% of LPG. The results were found to be reproducible up to 96 % after 3 months. Response and recovery times for LPG sensing were found to be 220 and 250 s. Best sensitivity, less hysteresis, small activation energy and good reproducibility identify that fabricated humidity and LPG sensors (B 2 ) are promising and challenging.