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SnO_2-In_2O_3 porous channel composite preparation process of CO gas sensing properties of

Author: PengYuanYuan
Tutor: CaoJianChun；ZhouXiaoLong
School: Kunming University of Science and Technology
Course: Materials Science
Keywords: Porous Road SnO2-In2O3 composites Rutile SnO2 First-principles Gas-sensitivity
CLC: TB381
Type: Master's thesis
Year: 2011
Downloads: 20
Quote: 0
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Abstract


Preparation process and the gas sensitivity of metal oxide semiconductor material, a direct impact on the performance of the gas sensor. Single SnO2 prepared or of In203 metal oxide semiconductor material gas sensor has poor stability, high selectivity, sensitivity and low, and in recent years, it was found that the composite material has good gas sensing performance of metal oxide, than better selectivity and sensitivity of a single metal oxide. Therefore, the study the Sn02-In203 composite material preparation process and the development of the gas sensing properties of this class of materials is of great significance. The Sn02-In203 composite for the study, conducted Sn02-In203 porous channel composite solid-phase sintering thermodynamics. By controlling Sn02 content, sintering temperature and compacting pressure and other process conditions, to obtain excellent pore structure the Sn02-In203 composite material. With the X-ray diffraction, scanning electron microscopy, gas sensing test system of modern analytical testing methods, micro microstructure of Sn02-In203 composites obtained after sintering, the volume shrinkage and CO gas sensing properties of test and analysis . And first-principles calculation and simulation of the Sn02 low index surfaces of CO adsorption mechanism. The final results are as follows: by the thermodynamic analysis found Sn02 and In203 of in TIn2O3 =, 1020.685K decomposition occurs TSnO2 1262.584K when, is not conducive to solid-phase sintering, Sn02 and In203 this composite material, below the 1262.584K less insulation, in order to facilitate low-temperature sintering the powder and in order to make the composite powder fully sintered at high temperatures for a short time sintering. Combination of thermodynamic analysis by analyzing the sintering temperature, to suppress the pressure as well as Sn02 content of the Sn02-In203 composite pass structure and CO sensitivity, ultimately Sn02-In203 porous channel composite solid phase sintering process: containing 30% Sn02 ITO and Sn02 mixed powder (sintered insulation 1H, bubbling oxygen) 93MPa (pressed sheet) → 873K → 1573K (sintered insulation 3H, pass oxygen) → furnace cooling to room temperature. With the increase of the sintering temperature, Sn02 final solution to the In203, grains grow up, pore structure and gas sensing SnO2-In203 composite microstructure and gas sensing performance impact analysis shows process parameters: changed; but along the pressing pressure is gradually increased, and substantially no change in the pore structure of the porous track Sn02-In203 composites; Sn02 content increases, the porous channel composite materials on the sensitivity of the CO gas has been improved. Density functional first-principles calculation and simulation results show that the rutile Sn02 {110}, {100} family of two low-index planes, the (110) plane compared to other low-index surfaces, the surface energy of the lowest, most structures stable; through surface the Sn02 oxidation (110) and Restore (110) surface of the electronic density of states comparative analysis shows that, restore the (110) surface conductivity, therefore, select Restore CO adsorption on the (110) plane simulation and calculation. Calculated adsorption energy, density of states and the electron population analysis found, CO reduction (110) surface adsorption sites Sn4C CO adsorption not only impact to the adsorption point Sn4c the electronic states density affect Sn5C distribution of electronic density of states of the inner atoms, resulting in the entire restore (110) surface of the conductive properties changed, and since the CO adsorption offset causes the Fermi energy, resulting in the rise of the Fermi energy, which is affecting the SnO2 surface conductance performance of important reasons, which ultimately affect the performance of the SnO2-In2O3 composites. Found by density functional first-principles simulation and calculation, the rutile SnO2 is a semiconductor surface-controlled gas sensor, good adsorption of CO, is a self-adsorption. Of the study of the of rutile SnO2 adsorption of CO Porous Road SnO2-In2O3 composite test CO gas sensitivity with increasing SnO2 concentration increases gives a theoretical basis, and gas sensing test.

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