| AB03perovskite metal oxides can be used in catalytic materials, magneto-impedance materials, high-temperature superconducting materials, gas-sensing meterials. The LaFeO3materials show good gas-sensing properties to the reducing gas. t has sound stability, good selectivity and excellent sensitivity. Another excellence is that its characteristic can be controlled to get even better by electing suitable A and B atoms or chemical doping in ABO3. ABO3material which has great theorical significance and utility value has aroused interest among the researchers. The miniaturization and the craft simplification is the premise of for the gas sensors to move toward the market application, the study of the craft has great meaning.In the present work, La0.75Ba0.25FeO3and La1-xSrxFeO3(x=0-0.3) nano crystaline weres separately prepared by the sol-gel method. The gas sensorses based on the materials are fabricated. We studied the influens of the material doping modification and the primary device craft to electricity performance and the gas performance’s influence of the gas sensor. The gas mechanism of La1-xSrxFeO3(x=0-0.3) has been further discussed. In addion, we carried on the preliminary exploration for the LaFeO3to the CO2survey application. Prime task and conclusion including the following three parts:1. In the present work, La0.75Ba0.25FeO3thick films were fabricated by printing the paste (mixture of La0.75Ba0.25FeO3powders and binder) on alumina substrate deposited with Ag electrodes. After the printing process, the thick films were finally annealed at various temperatures. We find out that the optimal final annealing temperature for the La0.75Ba0.25FeO3thick film, which is made from La0.75Ba0.25FeO3powders annealed at800℃for3h, to obtain a large sensing response is about700℃. The gas sensing properties of La0.75Ba0.25FeO3thick film sensors also depend on the thickness of the dry film. The film with thickness of D=50μm exhibits the largest response among the four thick films (D=30,50,70 and100μm). La0.75Ba0.25FeO3thick film sensors can detect acetone and ethanol with very low concentrations (i.e.,5ppm).2. The La1-xSrxFeO3(x=0,0.1,0.2) nano crystaline perpared by the sol-gel method are annealed under800℃for3h, and the tubular-packed gas sensorses nnealed under400℃fot2h. the XPS analysis to La1-xSrxFeO3show that the Sr-doping does not change LaFeO3the crystal structure, When lanthanum ion is substitutd by Sr, the lattice parameter increaces leading to an increment of unit cell, which has hindered the grain growth; The Sr doping can reduce the resistance of the La1-xSrxFeO3material, when x=0.1, the electric conductivity of the materials is best. Sr doping enormous enhancement the sensitive performance of the materials. And when x=0.2, the gas sensitive performance has achieved the maximum value, to500ppm ethanol,the response is327; with the increas of the Sr-doping, the Fe4+/Fe3+proportion increases gradually, the Oad/Olattice proportion reduces gradually, but the gas performance and the gas performance height elevates along with the Fe4+proportion increases.3. We studied the gas sensing performance of the LaFeO3system to CO2.800℃La1-xSrxFeO3(x=0-0.3) and La0.75Ba0.25FeO3nano crystaline perpared by the sol-gel method are annealed under800℃for3h,the tubular-packed gas sensorses were annealed under600℃for2h. The La1-xSrxFeO3(x=0,0.1,0.2,0.3) sensors show certain gas performance to CO2in380℃. when x=0, the gas performance is not obvious, gas performance along with x increases, when x=0.2is best, the sensitivity achieves1.36to4000ppm CO2. The lagerest sensitivity of La0.75Ba0.25FeO3sensors to4000ppm CO2is3.5in100℃. The work temperature is much lower than La1-xSrxFeO3.At the same time, we carried on the experiment to the SnO2nanometer crystal material and the La0.75Ba0.25FeO3nanometer crystal material’s mix, and measured the gas sensing of the mixed material to CO2. It was unable using the sol mix to prepare the La0.75Ba0.25FeO3nanometer crystal material and the SnO2material mixture successfully directly. The new material is produced, and shows a certain CO2sensitive performance in400℃; We directly mix the SnO2material and the La0.75Ba0.25FeO3nano crystaline and prepared the gas sensors. The CO2gas performance of the mixed is lower than the pure La0.75Ba0.25FeO3nano crystaline, achieves about2.8to4000ppm CO2gas. But the operating temperature slightly has the drop to80℃.In summary, perovskite nano-crystalline Sr, Ba-doping LaFeO3is studied by experimental method。The electrical properties and gas-sensing properties of the materials are measured, We gain further insight into the gas-sensing mechanism of LaFeO3.The fabricated of thick-films gas sensor are studied。... |
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