Study On Low Resistance Methane Gas Sensors Based On Tin Dioxide

Methane is widely distributed in nature and is the main component of natural gas,biogas,and pit gas.As a clean fuel,it is widely used in civil and industrial scenarios.In standard state,methane gas is colorless and odorless.When the methane concentration in the air reaches 25%?30%,it can cause headache,dizziness,fatigue and other symptoms.In severe cases,it can cause suffocation and death.Therefore,it is of great significance to use methane gas sensors to monitor the environment in real time.The metal oxide semiconductor-based methane gas sensor has the advantages of small device size and simple operation,and has broad application prospects in mining,industrial production,and household safety.At present,metal oxide semiconductor sensitive materials for methane gas sensors have been extensively studied.Related materials include SnO₂,ZnO,TiO₂,etc.With the continuous advancement of material synthesis technology,the composition and morphology of sensitive materials have become more diverse.Although the construction of the micro-nano morphology of sensitive materials promotes the improvement of sensor sensitivity,it also causes an increase in device power consumption and manufacturing costs,making the industrialization and commercialization of this sensor type more difficult.Therefore,this article mainly focuses on the research of metal oxide semiconductor methane gas sensor with low cost,controllable resistance and high sensitivity.The main research contents are as follows:(1)The SnO₂ material doped with Pd was prepared by the sol-gel method,and on this basis,divalent metal cations(Ca,Mg,Sr)were doped to adjust the resistance of the sensor.Through a series of gas sensing characteristic tests,it can be found and proved that doping with Ca,Mg,Sr elements can increase the basic resistance of the sensor.At330?,when the Ca doping amount is 0.25 wt%,the resistance increases from 63.4 k?to 71.6 k?.It has the highest sensitivity when the doping amount of Ca is 0.5 wt%.At its optimal working temperature(300?),the sensitivity to 1000ppm CH₄ is 8.36,and the response recovery time is 2s and 6s,respectively.At a gas concentration of 1200ppm,the concentration has a good linear relationship with the response value.The enhanced gas sensitivity is attributed to the catalytic effect of the metal(Pd)and the increased oxygen vacancy ratio.(2)SnO₂ nanoparticles doped with Pd elements are used as the matrix material,and pentavalent metal elements(Sb and V)are doped and introduced.Through experimental tests,it is found that doping of Sb element has the most obvious effect on reducing resistance,and when the doping amount is 1 wt%,the effect of reducing resistance is the best.At 320?,the resistance value drops from 63.4 k?to 11.0 k?.At the optimal working temperature of 280?,the response of the sensor with 1 wt%Sb doping in an atmosphere of 1000ppm CH₄ is 5.39,and the response and recovery time of the sensor are 2s and 9s,respectively.In addition,the sensor exhibits stable and repeatable resistance changes(the resistance in air is 45 k?±5 k?,and the resistance value in1000ppm methane atmosphere is 9 k?±3 k?).The main content of this paper is divided into the above two parts,through the doping of divalent and pentavalent metal elements to realize the control of the increase and decrease of sensor resistance,respectively.It proposes a new reference scheme for constructing a metal oxide semiconductor methane gas sensor with controllable resistance.