The Research Of Perovskite-type Er_1-xYb_xFeO₃ Gas-sensing Materials Composition,Surface Sensitization And Sensing Mechanism

Semiconductor gas sensor provide a kind of effective solution for detecting and monitoring the VOCs in the air.As an important part of gas sensor,gas sensing material is crucial to the gas performance.Perovskite rear-earth ferrites have aroused the interests of researchers because of the stabilities and various chemical and physical properties.Meanwhile,loading noble metal on rear-earth ferrites can enhance the gas sensitivity.This project fabricated new perovskite rear-earth ferrites-Er_1-xYb_xFeO₃ and researched the influence of ratio of Er to Yb.Furthermore,we synthesized the Ag/Er_0.7Yb_0.3FeO₃ and used the surface sensitization of Ag for enhancing the gas sensing properties of Er_0.7Yb_0.3FeO₃.And then sensing mechanism was researched.Among Er_1-xYb_xFeO₃?x=0,0.3,0.7,1?sensing materials,Er_0.7Yb_0.3FeO₃ material presented the best gas sensing performance which showed the respond value 12 towards the 10ppm butanone and 2.8 towards the as low as 0.5ppm butanone.The excellent performance of Er_1-xYb_xFeO₃ comes from the unique band structure,stable crystal structure and porous micromorphology.Meanwhile,the enhanced sensing performance of Er_0.7Yb_0.3FeO₃ can be attributed to the higher electronic density of states at the top of valence band than those of materials with single element of A site,and to larger hole size than that of material with the ratio of Er to Yb is 3:7.Ag/Er_0.7Yb_0.3FeO₃ gas sensing materials with Ag nanoparticles being decorated on the surface of porous Er_0.7Yb_0.3FeO₃ particles presented the better gas sensing performance.In particularly,Ag/Er_0.7Yb_0.3FeO₃-2,in which Ag to Er_0.7Yb_0.3FeO₃ is1:100,showed the highest respond value 48.9 toward 10 ppm butanone,which is 8times the gas sensitivity of Er_0.7Yb_0.3FeO₃.This is ascribed to the electronic and chemical sensitization.Electronic sensitization refers to Ag can absorb elctrons from the basic material,which largely enhances the number of hole carriers?R_a reduce?.Chemical sensitization refers to Ag can increase surface chemisorption oxygen and bring sprillover effect,which make more electrons released back to basic material when exposed to target gas.The improved gas sensing properties of Ag/Er_0.7Yb_0.3FeO₃-2 owes to that Ag nanoparticles with the size about 50-100nm are less than that of the size of about 15nm.Therefore,loaded Ag in sample 2 can use the function of electronic and chemical sensitization better,which contributes to the enhancement of sensitivity.