Preparation And Gas-Sensing Properties Of Indium Oxide And Zirconium Oxide/Indium Oxide-Based Sensors

With the continuous development of human industrial production levels,exhaust emissions have to some extent affected the atmospheric environment,air pollution has become a pressing environmental issue.Volatile organic pollutants（VOCs）such as acetone,ethanol and butanol,for example,are a constant threat to the ecological environment with their carcinogenic,teratogenic and mutagenic effects.The main sources of VOCs are natural organisms and anthropogenic emissions.To ensure that emissions of VOCs are below prevention and control standards,the preparation of gas sensors with the ability to rapidly monitor and accurately detect has become a research priority.Indium oxide（In₂O₃）is a metal oxide with a broad forbidden band,low resistance and good sensitivity.It possesses adsorption properties with strong interactions with gas molecules and is therefore widely used in gas sensors.One-dimensional nanofibres with high specific surface area,high permeability,small pore size and good pore interconnectivity.Therefore,in this thesis,In₂O₃ nanofibres and ZrO₂/In₂O₃ heterojunction composite nanofibres doped with zirconium oxide（ZrO₂）were prepared by electrostatic spinning method,and scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction mapping（XRD）,N₂adsorption,X-ray energy spectrum analysis（EDS）,X-ray photoelectron spectroscopy（XPS）and other techniques were used to analyse the The morphological composition and other characteristics of In₂O₃ and ZrO₂/In₂O₃ were investigated in detail by gas-sensitive tests.In addition,the gas-sensitive mechanism of the In₂O₃ and ZrO₂/In₂O₃adsorption mass transfer processes is proposed.（1）In₂O₃ nanofibres were synthesised by electrostatic spinning and the effects of the synthesis conditions on the microscopic morphology and gas-sensitive properties of In₂O₃ were investigated;the microscopic morphology of In₂O₃ showed that the synthesised fibres were highly crystalline and the fibre structure was intact;the BET data showed that the specific surface area of the samples reached 62.423 m²/g.The gas-sensitive properties of the synthesised In₂O₃ samples were tested under different conditions.The gas-sensitive data showed that samples synthesised at a PVP concentration of 6.25%,a calcination temperature of 500°C,a calcination rate of 5°C/min and a calcination time of 2 h achieved a response to 100 ppm acetone gas of 37.9 at an operating temperature of 200°C.Based on the results of the response cycle tests,it was deduced that the sensor could be used in a gaseous environment for several times.Continuous testing for 30 days proved that the material has excellent stability.Mechanistic analysis reveals a high number of carriers inside In₂O₃,which has a significant change in the crystal potential barrier during adsorption and mass transfer,produces a high response to reducing gases.The response values vary with the magnitude of their change.（2）ZrO₂/In₂O₃ composite nanofibers doped with ZrO₂ were synthesized by electrostatic spinning method,and the characterization results showed that homogeneous nanofibers were obtained,and some in situ grown octahedral-like particles appeared in the nanofibers.The number of particles in the fibres increased significantly with increasing ZrO₂ content.Based on gas-sensitive performance tests,it is known that the response values are significantly higher compared to In₂O₃ nanofibres.The response to 100 ppm acetone gas at an operating temperature of 260°C with a doping ratio of 5:1 is 60.4,which is 1.59 times higher than that of In₂O₃.It also has good stability and fast response times.Analysis of the gas-sensitive mechanism shows that doping increases the carrier density and enhances carrier migration during operation,resulting in significant performance improvements.