Influence of the variation in hydrothermal reaction time on the structural, optical and electrical properties of NiTiO₃ perovskite and its application for gas sensing

In this work we report the hydrothermal method for the synthesis of NiTiO₃ perovskite nanoparticles (NPs). The influence of reaction time variation (6 h, 12 h, 18 h and 24 h) on the synthesis of NiTiO₃ NPs was studied. The synthesized material with variation in reaction time was characterized by various characterization methods like UV-Visible Spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM), High resolution transmission electron microscopy (HRTEM) and Selected area electron diffraction (SAED). Band gaps of the material synthesized by varying reaction time were studied and it was found that band gap decreases on increase in reaction time. The various structural parameters of the NiTiO₃ like crystallite size, dislocation density and microstrain were calculated from XRD data. From the FESEM analysis, average particle size was estimated and found to increase in the range of 32 nm to 37 nm as reaction time increased from 6 h to 24 h. The electrical properties of the material were studied. The gas sensing performance of NiTiO₃ thick films was tested on static gas sensing unit for various gases such as H₂S, CO, CO₂, Cl₂, NH₃, Ethanol and LPG. It showed maximum response to CO₂ gas at room temperature (RT) for sample synthesized at 24 h reaction time which is attributed to the disappearance of TiO₂ phases. The repeatability and long term stability of the sensor were also studied.