Preparation And Gas Sensing Properties Of Rare Earth Doping Zno Nanofibers

ZnO is a II-VI compound semiconductor with a direct and wide bandgap of3.37eV. The exciton binding energy is60meV at room temperature. It has a hexagonal wurtzite structure, which belongs to the space group P63mc. Its lattice parameters are a=0.325nm and c=0.521nm, respectively. ZnO has excellent electronic, optical, piezoelectricity, gas sensing properties etc. So ZnO has comprehensive applications in many important research fields.In this paper, various kinds of ZnO nanofibers have been prepared by electrospinning method. These ZnO nanofibers are pure ZnO nanofibers and ZnO nanofibers doped by Ce-. La and Er. The process of electrospinning was systematically discussed by adjusting conditions such as concentration of PVA, electrospinning voltage and receiving distance, the content of mineral salt, sintering temperature etc. After preparation, the optimal fabrication parameters were got as follows:concentration of PVA solution is10%, electrospinning voltage is10kV, receiving distance is20cm, weight ratio of PVA to mineral salt is1:1, sintering temperature is650℃and sintering time is2.5h. ZnO nanofibers doped by rare earth elements have been fabricated in accordance with these optimal parameters. The crystal structure and morphology of specimens were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The optical and gas sensing properties were measured by photoluminescence spectrum and gas sensing testing system. The effects of different rare-earth dopants and doping content on the gas sensing properties of ZnO nanofibers were systematically discussed in the aspects as sensitivity, response and recovery time, selectivity, working temperature, etc. The tested gases are H2S、C2H5OH、 CH3COCH3、 CH3OH、 HCHO、 CO and NO.The results show that:compared with pure ZnO nanofiber sensors, Ce dopant could improve the gas sensitivity to acetone steam. Among all, the sensitivity to acetone steam peaks when Ce doping content reaches6at.%. Besides, this also lower the working temperature and accelerate the response and recovery rate. The sensitivity to lOppm H2S increases obviously after doping La. The sensitivity to H2S rises with the increasing of La content. The sensitivity to H2S peaks when La doping content reaches3at.%. Besides, it also has quick response and recovery rate and good selectivity. The sensitivity to H2S with low concentration also increases substantially after doping Er. The sensitivity to H2S peaks when Er doping content reaches1at.%. Er dopant can also lower working temperature, accelerate the response and recovery rate and have good selectivity to the testing gases.