Preparation And Characterizations Of Indium Oxides And Indium Oxide/polymer Composites

Indium oxide with wide band gap is an important n-type semiconductor, it hassmaller resistivity and high catalytic activity. Indium oxide materials showed goodsensing properties of the oxidizing gas and reducing gas and it was used in thesemiconductor gas sensor. The performance of semiconductor gas sensors, such assensitivity, selectivity, stability, response/recovery time, the physical and chemicalproperties of the gas sensing material,has a direct relationship with its morphology andstructure. According to the literature, semiconductor and polymer composite and dopingwith certain non-metallic elements also has some excellent properties and applications.In this thesis, nitrogen-doped indium oxide was synthesized at220℃viahydrothermal method using sodium azide as nitrogen source. These products werecharacterized by XRD, Raman, SEM, TEM, FTIR, XPS and UV-Vis. The average sizeof the dispersed nitrogen-doped In₂O₃nanoparticles is about30nm. It also explores theinfluence of the quantity of doped nitrogen to its morphology and gas-sensitive nature.The samples have good sensitivity to ammonia and ethanol at room temperature, andhave a good linear sensitivity to ethanol at300℃to different concentration. Theresponse time is10min and sensitivity is6for5ppm ammonia. The sensitivity canreach15for50ppm ammonia.We obtained two kinds of hexagonal and cubic indium oxide crystal usingdendritic-like InOOH as Precursor via the roasting method by controlling the heatingrate, the calcination temperature and time. XRD, SEM, FTIR and TGA-DTA were usedto characterize the products and the results show that the two kinds of pure indiumoxide of different phase is accordance with the morphology of the dendrite-likeprecursor. Explore gas sensitivity of dendrite-like cubic, hexagonal indium oxide andprepared nano-size indium oxide in laboratory, the result show that the cubic andhexagonal indium oxide are sensitive to ethanol and ammonia, especially the sensitivityof the hexagonal indium oxide has good sensitivity nanoparticles of indium oxiderelative to the other two material.Four kinds of composition materials was synthesized via chemical oxidationpolymerized pyrrole on the c-In₂O₃and h-In₂O₃base body. The products werecharacterized by SEM, FTIR and TGA-DTA, the results showed that the c-In₂O₃/PPycomposite have fast response time to ammonia and has a good linear relationship for different concentrations at room temperature.