Study On Gas Sensing Performance Of Different Type Oxides(ZnO,BiFeO₃)assisted By Optical And Magnetic Excitation

Metal semiconducting oxide gas sensors have been widely used because of their simplicity,low cost and stable performance.As the main excitation and activation means of such gas sensor,thermal excitation has been playing a leading role in excitation of gas sensitive response for a long time.With the increasing demand for the integration and miniaturization of sensors,various excited methods such as optical and magnetic excitation methods have come into the research vision gradually.According to different types of metal oxide semiconductor,this study chose ZnO and BiFeO₃ as the core gas sensing materials,which have large difference in forbidden band width and electromagnetic polarization intensity.On the basis of thermal excitation,the ultraviolet light and magnetic field were introduced into the gas sensor testing environment to study the sensing performance and various mechanisms.In view of ZnO has wide forbidden band width and weaker electromagnetic polarization,ZnO nanoparticles with different crystal size and pore size distribution were synthesized from Zn-MOF template by second ligand modulating crystal nucleation and growth rates.ZnO sensor with assemble structure has a response value of 14 toward 1 ppm n-butanol,which has good sensing performance.The selective response of gas molecules with different diameters by a single material is realized.The introduction of ultraviolet light excitation can make the ZnO gas sensor with broad band gap realize room-temperature gas sensitive response.The reason is that ultraviolet light excites a large number of valence band electrons to the conduction band,which makes the carrier concentration inside ZnO increase,and that is advantageous for further study of room temperature gas sensor model.The optimal operating temperature of ZnO gas sensor whose polarization intensity is only 0.02C/m² is reduced by 23? and ZnO show the highest response to butanone by magnetic excitation.The reason is that introduction of magnetic field can change the electron motion of some materials with certain polarization intensity,and decreases reaction activation energy of the surface adsorption oxygen ion with unpaired electrons and VOCs molecules with high electron cloud asymmetry degree.In view of BiFeO₃ has narrow forbidden band width and stronger electromagnetic polarization,BiFeO₃ samples were prepared through hydrothermal method and sol-gel method,Ba_0.05Bi_0.95Fe O₃ was successfully prepared by doping Ba into A-site of perovskite BiFeO₃ structure.By thermal excitation,BiFeO₃ gas sensor has a value of 1.32 toward 1 ppm n-butanol,and has good stability.After introducing ultraviolet light excitation,perovskite ferrite BiFeO₃ with narrow band gap decreased the optimal working temperature by 15?,the introduction of Ba element can rich electronic density states near the Fermi level,optimization of working temperature effect of Ba_0.05Bi_0.95Fe O₃gas sensitive material under ultraviolet light excitation is more obvious,which can be decreased by 90?.After introducing magnetic field,the response time of BiFeO₃ with polarization intensity of 1 C/m² is shorten by nearly 2 times,but the sensitivity became lower.The reason is that the introduction of magnetic field increases the magnetic domain turning and net magnetic moment of BiFeO₃,and the reduction of domain wall aggregation effect leads to the decrease of defect content,thus reducing the amount of surface adsorbed oxygen species.