Synthesis And Gas Sensing Performance Of Samarium Based Perovskite Nanofibers

With the continuous improvement of living standard,an increasing number of people pay attention to the threat caused by various toxic gases to health.This is of great importance for people’s life to detect volatile toxic and harmful gases effectively.Gas sensor has been widely used in civil and industrial fields as a device to detect gas composition and concentration.In recent years,the perovskite oxides ABO₃ have exhibited a variety of excellent physical and chemical properties,including high redox activity,electrocatalytic activity and crystal structure stability due to its unique crystal structure.Therefore,it has aroused widespread attention among gas sensor researchers.This paper is based on the diversity of B-site elements of perovskite and the advantage of A-site doping to improve gas sensing performance.The SmFeO₃ nanofibers were prepared by electrospinning.On this basis,the reasons for the difference of gas sensitivity between SmFeO₃ and Sm Co O₃ with different B sites were analyzed.Finally,the gas sensing properties of SmFeO₃ were improved by the method of rare earth A substitution doping.All of the as-prepared samples exhibit good selectivity to ethylene glycol.The main research work is as follows:1.One-dimensional SmFeO₃ nanofibers were successfully prepared by electrospinning and annealing treatment at 700℃.The SmFeO₃ nanofibers have rough surface and good gas sensitivity to ethylene glycol,indicating that the SmFeO₃ nanofibers can be used as an excellent ethylene glycol gas sensor material.2.Optimized the last experiment to reduce the working temperature of the material.The SmFeO₃ and Sm Co O₃ nanofibers with different B sites were prepared using the same electrospinning method and annealing treatment.The XRD refinement technology was employed to calculate the lattice parameters and B-O-B angle,and the distortion degree of the material structure was evaluated by combining tolerance factor t.The distortion of the SmFeO₃ structure is more obvious.The materials were characterized by SEM,BET and XPS,and the gas sensing performances of SmFeO₃and Sm Co O₃ sensors were compared.The results show that the response value of SmFeO₃ nanofibers sensor reaches14.3 to 100 ppm ethylene glycol at 200℃,which is almost 6.5 times that of Sm Co O₃nanofibers.The possible reason is that the SmFeO₃nanofiber has larger pore size,more oxygen vacancy,greater distortion degree and lower electrical conductance.Finally,based on the model of hole accumulation layer,the gas-sensitive mechanism was explained.3.In order to further improve the gas sensing performance of the SmFeO₃ sensor,the Sm_1-xHo_xFe O₃（0≤x≤0.07）nanofibers material were prepared.The results show that the substitution doping of Ho improves the gas sensitivity of the material to ethylene glycol.The Sm_0.95Ho_0.05Fe O₃ nanofibers have the best gas sensitivity,especially for the low concentration of 5 ppm ethylene glycol,it still has a high response value of 10.2.Various characterization results show that Sm_0.95Ho_0.05Fe O₃nanofibers have smaller grain size and higher porosity.