Sol–gel-processed CNT-doped LaFeO₃ and its application as LPG sensor

In the past few decades, perovskite materials have attracted the attention in research due to a wide range of applications in sensors and solid-state fuel cells. Perovskite lanthanum ferrite has also significant importance in LPG and humidity sensors for its photocatalytic activity and temperature-dependent surface morphology. The doping of CNT in perovskite ceramics plays a vital role in enhancing surface activity. CNT-doped Lanthanum ferrite sample was prepared by Sol–gel process. The well-prepared lanthanum ferrite samples were characterized for thermal, crystallographic, surface morphological, molecular, and optical studies. Differential scanning calorimetry study shows the clear crystallization of LaFeO₃ after decomposition and removal of organic species. X-ray diffraction study also confirms the crystallization of cubic LaFeO₃ with a minimum crystallite size of 38 nm. Scanning electron microscopic studies of lanthanum ferrite pellet and thick-film samples show the presence of large number of pores in uniformly distributed grains and particles. The pores in the thick-film sample were found to be higher in the pellet sample. XPS and EDS analysis confirm the elemental composition as La, Fe, O, and C. The optical band gap of the composite material was found to be 4.05 eV. The increase in band gap with LPG exposure on sensing element is also validated by DFT analysis. The maximum values of percentage sensor responses were found to be 431 and 480 at 5000-ppm LPG for pellet and film, respectively for LPG sensing. The thick film shows a better response in comparison to pellet over the entire range of gas sensing. The doping of 1 mol% CNT in lanthanum ferrite enhances the sensor response significantly.