Effect of synthesis route on electrical and ethanol sensing characteristics for LaFeO_3-δ nanoparticles by citric sol-gel method

Highlights: • LaFeO_3-δ nanoparticles were prepared by citric sol-gel method. • The effect of synthesis route, specifically the choosing of EG or PEG as raw material and calcination process, on the electrical and ethanol sensing characteristics were investigated for the first time. • The reason for the improvement of sensitivity was analyzed by the consideration of surface morphology and surface composition. - Abstract: LaFeO_3-δ nanoparticles were prepared by citric sol-gel method with different raw material choosing and calcination process. The choosing of polyethylene glycol instead of ethylene glycol as raw material and additional pre-calcination at 400 °C rather than direct calcination at 600 °C could result in the decrease of resistance due to the reduction of activation energy Ea. Meanwhile, the choosing of ethylene glycol as raw material and additional pre-calcination leads to the enhancement of sensitivity to ethanol. Comprehensive analysis on the sensitivity and XRD, SEM, TEM, XPS results indicates that the sensing performance of LaFeO_3-δ should be mainly determined by the adsorbed oxygen species on Fe ions, with certain contribution from native active oxygen. The best sensitivity of 46.1–200 ppm ethanol at prime working temperature of 112 °C is obtained by the sample using ethylene glycol as raw material with additional pre-calcination, which originates from its uniformly-sized and well-dispersed particles as well as high atomic ratio of Fe/La at surface region.