Influence Of Doping And Surface Modification On Gas Sensing Properties Of Metal Oxide Gas Sensors

Because of many advantages such as low price,quick response and small volume,the MOS(metal oxide semiconductor)gas sensors have been widely applied in gas detecting.Nevertheless,there are some shortcomings such as low selectivity and high working temperature,which are adverse to applications of the MOS gas sensors in practice.With the purpose of overcoming these shortcomings,this paper will adopt doping and surface modification to improve the properties of the MOS gas sensors and their operational performance.In this paper,22 kinds of doped nano zinc oxide(Zn O)gas sensing materials were prepared by mechanical ball milling method and printed on the 8-array substrate by screen printing,and the 8-array Zn O gas senors were obtained after drying and sintering.Alcohol,acetone and benzene,with concentrations of 0.02%,0.12%,0.04%,respectively,were used to test the gas sensing properties of the different doped Zn O gas sensors.And the effects of chemical properties of the dopants on their gas sensing properties were discussed.It indicated that the ionic radii play an important role on the sensing properties of the sensors,the best performance of the sensors to the measured gases were obtained when their ionic radii are in the range of 0.072 nm to 0.088 nm,which are close to the zinc ion radius.Besides,their periods of the dopants have a certain effect on the gas sensing properties of the gas sensors,and the valence barely affect the properties of the gas sensors.Mesoporous SnO2 powders were prepared by sol-gel method and characterized.SnO2 mixed with glass frit was modified with mesoporous SnO2 by screen printing.The concentration of the volatile organic compounds(alcohol,acetone and benzene)and H2 were 100 ppm and 1000 ppm,respectively.The effects of surface modification on the gas sensing properties of SnO2 were discussed.It showed that the gas sensing properties on the measured gases were greatly enhanced after surface modifying with mesoporous SnO2.The responses to 1000 ppm H2 increased from 2.8 to 16 at 300?,and the selectivity of H2 were improved by surface modification.Then the surface of SnO2 were modified with mesoporous SnO2 by slide-off transfer printing,and alcohol,acetone,benzene and H2 were used to test the gas sensing properties.The results showed that the working temperature of SnO2 sensors decreased from 300? to 250?,the responses were enhanced by the transfer printing.Compared to screen printing,the acetone sensing properties of the SnO2 gas sensors made by transfer printing were more excellent,the sensing properties towards alcohol and benzene were close,and the H2 sensing properties were worse.