Hydrothermally synthesized nanostructured NiTiO₃ thick films for H₂S and room temperature CO₂ gas sensing

In this work we are presenting the hydrothermal method to synthesize NiTiO₃ perovskite nanoparticles (NPs). The effect of variation in reaction temperature on the structural, optical, electrical and gas sensing properties of NiTiO₃ nanoparticles was investigated. The nanoparticles synthesized at different reaction temperatures were characterized by various characterization methods like XRD, FTIR, UV–Visible Spectroscopy, FESEM, TEM, HRTEM and SAED. The results of UV–Visible analysis revealed that band gap of NiTiO₃ decreased from 2.90 to 2.56 eV on increase in reaction temperature from 140 to 200 °C. The XRD analysis showed that crystallite size decreased in the range of 21 to 12 nm on increase in reaction temperature. The various parameters of the material like dislocation density, microstrain and crystallinity were also calculated from XRD data. The average particle size was estimated by FESEM analysis and found to be decreased on increase in reaction temperature. FTIR analysis confirmed the formation of NiTiO₃. Study of electrical properties proved the semiconducting behaviour of NiTiO₃. The detail analysis of NiTiO₃ sensor characteristics in terms of sensitivity, selectivity, response and recovery time was carried out. The study of gas sensing performance of NiTiO₃ revealed that NiTiO₃ synthesized at 140 °C showed maximum sensitivity to CO₂ gas at room temperature, whereas NiTiO₃ synthesized at 200 °C showed maximum sensitivity to H₂S gas at 250 °C.