气敏传感器的器件结构优化和敏感材料研究

发布时间：2018-09-18 10:58

【摘要】：采用SnO_2制备的气敏传感器具有生产成本低、结构简单、灵敏度高等优点,是最早商业化和量产化的气敏传感器之一。本文以掺锑的纳米SnO_2粉体为基础,尝试从贵金属掺杂和结构改进两方面来改善SnO_2气敏元件的气敏性能。本文的主要研究内容与结果如下:通过厚膜丝网印刷技术制备了不同电阻值的微加热器,测量了加热功率和温度的关系以及相同功率下的3D热分布图和环境温度对加热器的影响,在兼顾加热速率和热稳定性的前提下,调整元件基片尺寸和加热器面积可以获得良好的加热效率,确保敏感材料能得到均匀稳定的加热。实验结果表明,微加热器元件升温速率快,加热层温度越稳定,有利于提高元件的稳定性。以SnCl_4·5H_2O、SbCl_3、尿素等为原料,采用溶胶凝胶法制备了纳米SnO_2气敏粉体,通过扫描电子透镜(SEM)、X射线衍射仪(XRD)等手段对纳米SnO_2粉体进行了观察和表征。测量结果表明,采用溶胶凝胶法制备的SnO_2粉体平均晶粒尺寸大小约为25nm,形貌为球形,锑离子进入SnO_2晶格中取代了锡离子,没有其他杂相。在SnO_2材料中分别掺入0.1mol%、0.3mol%和0.5mol%的锑,测量了元件的气敏性能,其中掺入0.1mol%锑的元件的性能最佳。实验研究了Ag、Pt掺杂对元件气敏性能的影响。实验结果表明Ag掺杂可以有效的抑制丙酮对乙醇的干扰。发现Pt掺杂使元件的灵敏度有了极大的提高,有望制备成高浓度乙醇元件。运用复阻抗分析法对元件的气敏机理进行了研究,结果表明,SnO_2气敏传感器的敏感作用在低浓度时主要来自于气敏材料中的晶界作用,材料的晶界作用达到饱和,灵敏度的提升主要来自元件电极表面与敏感材料之间的相互作用。因此,改善电极材料的表面结构以及选择电极材料对提高元件的灵敏度有重要的作用。研究了不同气敏材料组成的双层厚膜结构对元件气敏特性的影响。发现双层厚膜结构可以改变气敏元件的灵敏度和选择性。这种改善与双层膜中不同气敏材料的上下排列顺序有很大关系。尽管上层膜的性能起主要作用,但下层膜的存在改变了材料的导电通路,因而改善了膜的气敏特性,其作用机制可能与双层厚膜界面处由于扩散效应所形成的过渡层有关。研究了环境湿度对气敏性能的影响,在SnO_2中气敏掺入硝酸镧,并通过调节元件加热功率的方法有效降低了湿度的影响,发现当加热功率为0.195W时,湿度对元件性能的影响最小。
[Abstract]:The gas sensor fabricated by SnO_2 has the advantages of low production cost, simple structure and high sensitivity. It is one of the earliest commercial and mass produced gas sensors. Based on the antimony doped nanometer SnO_2 powder, this paper attempts to improve the gas sensing performance of SnO_2 gas sensor from the aspects of noble metal doping and structure improvement. The main contents and results of this paper are as follows: microheater with different resistance values was fabricated by thick film screen printing technology. The relationship between heating power and temperature and the effects of 3D heat distribution and ambient temperature on the heater were measured. The heating rate and thermal stability were taken into account. Good heating efficiency can be obtained by adjusting element substrate size and heater area to ensure uniform and stable heating of sensitive materials. The experimental results show that the higher the heating rate is, the more stable the heating layer is, and the better the stability of the element is. Nano-sized SnO_2 gas-sensing powders were prepared by sol-gel method using SnCl_4 _ 5H _ 2O-SbCl _ 3 and urea as raw materials. The nano-sized SnO_2 powders were observed and characterized by scanning electron lens (SEM) X-ray diffractometer (XRD). The results show that the average grain size of SnO_2 powders prepared by sol-gel method is about 25 nm, and the morphology is spherical. Antimony ions have replaced tin ions in SnO_2 lattice, and there are no other heterophases. The gas sensing properties of the element were measured by doping 0.1 mol% and 0.5 mol% of antimony into the SnO_2 material respectively, and the element with 0.1 mol% antimony was the best. The effect of Ag,Pt doping on the gas sensing properties of the elements was investigated experimentally. The experimental results show that Ag doping can effectively inhibit the interference of acetone to ethanol. It was found that Pt doping greatly improved the sensitivity of the element and was expected to be used as a high concentration ethanol element. The gas sensing mechanism of the gas sensor is studied by complex impedance analysis. The results show that the sensitivity of SnO-2 gas sensor is mainly due to the grain boundary action in the gas sensing material at low concentration, and the grain boundary effect of the material reaches saturation. The enhancement of sensitivity comes mainly from the interaction between the electrode surface and the sensitive material. Therefore, improving the surface structure of electrode materials and selecting electrode materials play an important role in improving the sensitivity of the elements. The effect of the double layer thick film structure with different gas sensing materials on the gas sensing characteristics of the components was studied. It is found that the sensitivity and selectivity of the gas sensor can be changed by the double layer thick film structure. This improvement is closely related to the arrangement of different gas sensing materials in the bilayer film. Although the properties of the upper layer play an important role, the existence of the lower layer changes the conductive path of the material, thus improving the gas sensitivity of the film. The mechanism may be related to the transition layer formed by the diffusion effect at the interface of the double layer thick film. The effect of ambient humidity on gas sensing performance was studied. Lanthanum nitrate was added into SnO_2, and the effect of humidity was effectively reduced by adjusting the heating power of the element. It was found that when the heating power was 0.195 W, the effect of humidity on the performance of the element was the least.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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