Preparation And Gas-sensing Performance Of Porous In₂O₃

Semiconductor gas sensor attracted great attentions as one kind of gas sensor, due to their portability of carrying, simple operation, low price and other advantages in rencent years.It is important to prepare different morphologies and structures gas sensing materials to improve gas sensing properties of gas sensors. In2O3 is a new semiconductor gas sensing material, has great application value for its wide band gap width, low resistivity and optimum operating temperature. And porous In2O3 with high porosity and specific surface area, which provide large contacting surface area for semiconductor and test gas, exhibit unique advantage in improving gas sensing performance of semiconductors. Therefore, it is a hot topic to design and synthesis a certain morphology porous In2O3 in semiconductor materials.In this work, We synthesis different morphologies and structures porous In2O3 in different preparation methods, and test their gas sensing properties to different gases. The main content of this thesis is as follows:1. The fabrication of monodisperse porous In2O3 microspheres. The porous In2O3 microspheres were synthesis via a simple hydrothermal method. After the uniform and monodisperse porous pure In2O3 microspheres were fabricated, we prepared the same amount of Fe(NO3)3, Ce(NO3)3, AgNO3, La(NO3)3 doped In2O3 microspheres respectively, as a result,Ce-doped In2O3 microspheres also have uniform sphericity. So, Compared to In3+,we doped3%, 7%, 10%, 15%, 20% mmol Ce(NO3)3, which influenced the composition and sructure of microspheres. We find that the 3% Ce-doped In2O3 microspheres have high sensing properties,and Ce exist in the lattice of In2O3, not existed as CeO2.2. The hierarhical structure of flower-like In2O3 were successful synthesized. As the solvent, water and DMF play an important role for the morphology of samples, regular flower-like In2O3 were obtained after calcining the precursor when their volume ratio was 1:1,however there were not any product when DMF were not involved. In(OH)3 precursor grew from nanoparticles to nanosheets, and then assembled the hierarhical flower In(OH)3.3. Hollow structure of In2O3 were fabricated when Cu2 O as template. Spherical and cubic Cu2 O as sacrificial templates were prepared by different routs, NaS2O3 as the etching agent according to the principle of pearson. When heating the solution, the S2O32-combined withCu2+to form complex, and the hollow In(OH)3 precursor gradually formed with the Cu2 O etching. But considering the anisotropr of cubic structure which hindered the growth of hollow cubic In(OH)3, we keep the PHvalue at about 12 by adding NaOH.4. 3D porous In2O3 networks were synthesized successfully. 3D vaporous In2O3 networks were prepared after a series of reactions of funeral alcohol under the heating in air,polymerization, Americanization, andcombustion, when funeral alcohol as the fuel and a transforming template. And the pore size distribution of vaporous In2O3 networks concentrated in 20 nm. Meanwhile, we also prepared the 3D ordered macroporous In2O3 networks. We fabricatd the 3D PMMA colloidal crystal template firstly, and then prepared In(NO3)3 precursor solution infiltrated the PMMA templates. 3D ordered macroporous In2O3 networks were obtained by calcining In(OH)3 precursor in a muffle furnace.5. The fabrication of material and device integration 2D sheets In2O3 gas sensor. Owing to the morphologies and structures of gas sensing materials would be destroyed after grinding,coating and aging in the process of preparing gas sensor. So, we synthesized material and device integration 2D sheets In2O3 gas sensor and the 2D sheets grown on the surfance of templates. A series of different morphologies In2S3 precursor gas sensors were obtained by changing the reaction condition. We tested one kind of gas sensor to gases, and the result show that the gas sensor has high gas sensing property to ethanol, the response value is about45 to 100 ppm ethanol at the optimum working temperature, which is about 280℃。6. The In2O3 gas sensing material were prepared when In2S3 as the precursor.The fabrication of flower-like In2O3 microspheres after calcining the In2S3 precursor. In the process of preparing In2O3 via a simple hydrothermal method, in addition to the In(OH)3 as the precursor, but also with In2S3, which is easier to get the product with hierarchical structure.The morphologies of the products are obvious hierarchical structure, pore distructure is uniform on the nanolayer. The gas sensing properties of gas sensor is better for ethanol.The obove porous In2O3 gas sensing materials with different morphologies and structures prepared by calcining the precursors, and high reaptability of experiments provided favorable factors for the preparation of the simple.