Study On Improving Gas Sensing Properties Of Bimetallic Oxide Materials Via Micro Control

Recently,with science and technology developing rapidly,people’s living standards continuous improvement,but it also brings many environmental pollution problems.There are a variety of toxic and harmful gases in the environment,which threaten people’s health.Therefore,developing a sensor with good selectivity,high sensitivity,and low working temperature is particularly significant.Among them,spinel type（AB₂O₄）and perovskite type（ABO₃）metal oxides become the focus of current research due to their unique structure.This article introduces the synthesis and gas sensing properties of NiFe₂O₄ and LaFeO₃ bimetallic oxide semiconductor materials.The main research contents are as follows:In the first part,we present a strategy to improve the gas sensing performance of NiFe₂O₄via controllable the heating rate of calcination to synthesize fluffy NiFe₂O₄ nanosheet-flowers.XRD、SEM、BET and XPS were used to characterize the crystal structure,morphology,specific surface area and surface structure.The gas-sensing performance were tested and the results demonstrated that the performance was strongly influenced by the specific surface area and oxygen vacancy content.The resultant NiFe₂O₄nanosheet-flowers with a heating rate of8°C/min,which has a fluffier morphology,more oxygen vacancies in the surface and larger specific surface area（87.0 m²/g）,exhibited enhanced response and shortened response time toward ethanol.In addition,the sensor can maintain a relatively stable response value in a long-term stability during 10 days.In the second part,we annealed La[Fe（CN）₆]·5H₂O precursor in air to obtain porous LaFeO₃.The XRD result showed that the LaFeO₃ material is pure phase.The results of SEM and TEM showed that LaFeO₃ material is porous hexagonal nanosheets.In addition,BET test results showed that the surface area of the material is 16.8 m²/g.The optical properties of LaFeO₃ are tested by UV-visible DRS technology,and the band gap value of LaFeO₃ is 2.3 e V.XPS results showed that the surface oxygen mainly exists in the form of lattice oxygen,oxygen vacancy and adsorbed oxygen,and the content of oxygen vacancy is as high as 41.9%.The results of gas-sensing performance test show that the sensor based on LaFeO₃ has a high response（17.5）to 100 ppm n-propanol at a lower working temperature of 100℃.In the cycling and stability tests,the response value of the sensor is maintained at about 17.5 and there is no obvious change,indicating that it has good long-term stability and repeatability.