Preparation and characterization of nanocrystalline nickel ferrite thin films for development of a gas sensor at room temperature

In the present work, synthesis and characterization of thin films of nanostructured nickel ferrite (NiFe₂O₄), and its employment as liquefied petroleum gas (LPG) and carbon dioxide gas (CO₂) sensors operable at room temperature (27 °C), have been reported. These thin films have been prepared using sol–gel spin coating technique. The structural and surface morphological properties of the fabricated films were studied by X-ray diffraction (XRD) and scanning electron microscopy, respectively. Single phase formation of inverse spinel structure (NiFe₂O₄) was confirmed by XRD data. The synthesized NiFe₂O₄ exhibits crystallite size ~23 nm, porosity ~38 % and specific surface area ~57 m² g⁻¹. In order to check the potential applicability of the fabricated films as gas sensor, the modulations in electrical behavior of the film had been recorded by exposure of LPG and CO₂ respectively, in a controlled gas chamber. The mechanism of gas sensing of NiFe₂O₄ thin film has been explained on the basis of surface adsorbed oxygen on the surface of a sensor. The sensing results show that the fabricated sensor is challenging for the leakage detection of LPG as it possesses high sensitivity, stable behavior in long run and small response and recovery times towards LPG.