The Preparation Of In₂O₃ And In₂O₃/Composites And Its Gas Sensitive Properties Research

Indium oxide is a typical n-type metal oxide semiconductor,it has a wide band gap（E_g=3.55-3.75 eV）,good conductivity,low resistivity.To date,indium oxide has been widely used in various applications such as electrical field emission,solar cells,photoelectrochemical and semiconductor gas sensors and so on.Because of its relatively low cost,and simple operation,hydrothermal method has attracted most attention in attempt to gain metal oxides nanomaterials.In order to improve the gas sensing properties of sensitive materials,the following aspects of In₂O₃ and In₂O₃/complexes were conducted:（1）In₂O₃ nanoparticles were successfully prepared by calcination of the precursor which was synthesized via a hydrothermal method using different templates。The crystal phase and morphology of obtained samples were characterized by XRD and SEM,gas sensing properties of sensors were tested by WS-30A system.Gas sensing test results indicated that the gas sensors made of In₂O₃ nanoparticles based on NaOH as a template have better selectivity and sensitivity to nitrogen dioxide（NO₂）gas.（2）In₂O₃/CuO composites were prepared with hydrothermal synthesis method using In（NO₃）₃·xH₂O and Cu（NO₃）₂·₃H₂O as raw materials and C₆H₁₂N₄ as template.The samples characterized by XRD and SEM,the sample shows cube with nanoparticles attached to the surface when n_（In）:n_（Cu）:n_（HMTA）=1:1:90,In₂O₃/CuO composites were evidenced.The effect of the amount of templates and different In:Cu were also discussed.Furthermore,the In₂O₃/CuO powder were coated on the surface of a ceramic tube to fabricate thick film gas sensors,which exhibited that the optimum working temperature is 200 ℃.In particular,the gas sensor based on In₂O₃/CuO composites showed much higher sensitivity than pure CuO and pure In₂O₃,which sensitivity in 10 ppm of NO₂ can reach up to 90.3.The response and recovery times of the gas sensor based on the In₂O₃/CuO composites were about 15 s and 25 s,respectively.（3）In₆WO₁₂ composites are prepared with hydrothermal synthesis method using In（NO₃）₃·xH₂O and Na₂WO₄·5H₂O as raw materials and C₆H₁₂N₄ as template.The crystal phase and morphology of obtained samples were characterized by XRD、SEM、BET and XPS,gas sensing properties of sensors were measured by WS-30A system.The SEM shown that that under the conditions of the molar ratio of indium nitrate and tungstic acid oxalate was 1:2.5 and hydrothermal synthesis temperature was 180 ℃,preparing the flower-shaped indium tungsten oxide powders 3-4μm size.The synthetic powder is prepared as sensitive membrane,the sensor had better response and selectivity for C₂H₅OH.