دانلود رایگان مقاله اثر مسیر سنتز بر ویژگی الکتریکی اتانول برای نانوذرات LaFeO3

Abstract

LaFeO3- 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 LaFeO3- 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.

4. Conclusions

In the present work, we experimentally investigated the effect of raw material choosing (EG or PEG) and calcination process on the electrical and ethanol sensing characteristics for LaFeO3- nanoparticles by sol-gel method. Compared to the sample choosing EG as raw material or with direct calcination at 600 ◦C, the choosing of PEG as raw material and additional pre-calcination at 400 ◦C can both resultin the decrease of resistance due to the reduction of activation energy Ea, which makes the hopping of small polarons much easier. Temperature dependence of sensitivity suggests 112 ◦C to be the prime working temperature for these sensors. The best sensitivity to 200 ppm ethanol at 112 ◦C is 46.1 obtained by the sample choosing EG as raw material with additional pre-calcination, which is ascribed to its uniformly-sized and well-dispersed particles as well as high atomic ratio of Fe/La on the surface of particles. Our work demonstrates that the choosing of EG as raw material and additional pre-calcination process during citric sol-gel method is benificial for the improvement of sensing performance for LaFeO3- nanoparticles.