Measures And Mechanism Of Improving Gas-sensing Properties Of ZnSnO₃

The gas-sensing materials that focused most recently are binary metal oxide semiconductors（like ZnO,SnO₂,WO₃）.However,there are still some gas-sensing problems,such as low response at high working temperature.As a new-style ternary composite metal oxide semiconductor,ZnSnO₃ shows a few advantages like environment-friendly,good selectivity and high response.But the working temperature of pure ZnSnO₃ is still too high as binary metal oxide semiconductors,and it hardly shows response at low temperature.It will be incapable of practical application if not solved.To solve these problems,ZnSnO₃ were synthesized by a simple hydrothermal method in this research,with the addition of different organic agents（TEOA,HMT,PEG-400,C₃H₄N₂）during the preparation.Moreover,nano-TiO₂ particles were used for surface decoration.At the same time,the detection of gas-sensing properties was taken under UV illumination.The results showed rounded cubes,surface-etched cubes and microspheres of the as-synthesized ZnSnO₃ samples with the addition of TEOA,HMT and PEG-400,respectively.But ZnO/SnO₂ mixtures were synthesized because of C₃H₄N₂.The probable reason for different morphologies may be as follows:In the preparation process,various organic agents protect different sites from erosion due to the steric effect.The composites of ZnSnO₃ rounded cubes and 10 wt.%nano-TiO₂ showed best response to ethanol at 80°C,which increased to 70.16.The gas-sensing mechanism indicated that UV light made a large number of photon-generated electron-hole pairs created,which resulted in the reaction between ethanol and more adsorbed oxygen ions.What’s more,TiO₂-ZnSnO₃ heterojunctions were formed,inhibiting the recombination of photon-generated electron-hole pairs.For surface-etched ZnSnO₃cubes,their response to 500 ppm ethanol at room temperature was 3.43,which made the ethanol detection of ZnSnO₃-based gas sensors realized preliminarily.It was obvious that the absorbance of surface-etched ZnSnO₃ cubes to the UV light was a bit higher,making more photon-generated electron-hole pairs created,and therefore the reaction between ethanol and adsorbed oxygen ions was promoted.In addition,surface-etched ZnSnO₃ cubes were in small size with hollow structure,which helped to the reaction.In summary,ZnSnO₃ samples with different morphologies were successfully synthesized with the addition of various organic agents during the preparation.The ethanol detection of ZnSnO₃-based gas sensors at room temperature was realized preliminarily.Due to the decoration of nano-TiO₂,the response of ZnSnO₃ was promoted at low temperature.At the same time,the growing mechanism and gas-sensing mechanism were proposed.