The Synthesis And Gas-sensing Research Of Three-dimensionally Ordered Macroporous LaFeO₃ Based Nanomaterial

With the development of industrialization, toxic and harmful gas emissions gradually affecting people's lives. To detect and control of these polluting gases, people's attention consequently focus on gas sensors. Due to its excellent gas sensing performance, perovskite-type semiconductor oxides have been extensively studied as gas sensing material.By PMMA colloidal crystal template method, three-dimensionally ordered macroporous(3DOM) LaFeO3-based gas sensing material with different pore sizes and different content of Mg2+ doping has been prepared. These samples have tested using SEM, EDS, XRD, HRTEM, nitrogen adsorption to analysis their microstructure, phase composition and surface morphology. Gas sensing properties are tested by the laboratory equipment under different conditions. The main contents and conclusions are as follows:(1) PMMA microspheres were prepared by soap-free emulsion method. And the PMMA colloidal crystal templates were synthesed through natural sedimentation, centrifugal sedimentation and vertical acceleration methods.(2) Template with different diameters PMMA microspheres of 280 nm, 380 nm, and 490 nm were prepared. And 3DOM LaFeO3 with different pore size were synthesised using these different size PMMA colloidal crystal template.(3) To determin the methanol gas sensing property, 3DOM La FeO3 with different pore sizes were tested. 3DOM LaFeO3 with 190 nm pore size exhibits the maximum response(96) to methanol, good selectivity, and shorter response and response times.(4) 3DOM structure La1-xMgxFeO3 by Mg2+ doping was successfully prepared using PMMA colloidal crystal template.(5) The incorporation of Mg2+ can significantly improve gas sensing properties of LaFeO3 to methanol, and the response gets its maximum value when x=0.05. But after doping content is greater than 5%, gas sensing properties of the material decreased. When the doping amount gets greater than 15%, the gas sensing performance is lower than the undoped 3DOM structure La FeO3. This is mainly due to the lower amount of Mg2+, which can increase internal and surface defects of material. This helps to improve the performance of gas-sensitive material, But an excess of Mg2+ incorporation, the internal defects stabilize in the material, which is not favor to gas-sensitive reactions.