The Effect of the Thickness of the Sensitive Layer on the Performance of the Accumulating NOx Sensor
The Effect of the Thickness of the Sensitive Layer on the Performance of the Accumulating NOx Sensor
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DOI：
10.3390/s120912329
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发表时间：
2012-09-01
期刊：
影响因子：
3.9
通讯作者：
Moos, Ralf
中科院分区：
文献类型：
--
作者：
Gross, Andrea;Richter, Miriam;Moos, Ralf
利用蓄积式传感器原理测量低浓度NOx是一种很有前途的新方法。在积分周期中，输入的NOx分子被存储在基于汽车稀薄NOx捕集器(LNT)材料的敏感层中，这种材料与存储的NOx的量成比例地改变其电阻率，使传感器适合长期检测低水平的NOx。研究了多层丝网印刷工艺制备的感光层厚度对感光性能的影响。所有样品对NO和NO2都表现出良好的蓄积传感性能。根据简化模型，敏感层的基阻和对NOx的敏感度随着厚度的增加而减小。相反，传感器的响应时间会增加。所有样品的线性测量范围在传感器响应约30%时结束，导致线性可检测量随厚度增加。因此，敏感层厚度的变化是使线性测量范围(与厚度成正比)以及灵敏度(与反厚度成正比)适应应用要求的有力工具。结合传感器模型和测量结果的计算表明，在线性范围内工作时，大约3%的LNT材料被转化为硝酸盐。
A novel and promising method to measure low levels of NOx utilizes the accumulating sensor principle. During an integration cycle, incoming NOx molecules are stored in a sensitive layer based on an automotive lean NOx trap (LNT) material that changes its electrical resistivity proportional to the amount of stored NOx, making the sensor suitable for long-term detection of low levels of NOx. In this study, the influence of the thickness of the sensitive layer, prepared by multiple screen-printing, is investigated. All samples show good accumulating sensing properties for both NO and NO2. In accordance to a simplified model, the base resistance of the sensitive layer and the sensitivity to NOx decrease with increasing thickness. Contrarily, the sensor response time increases. The linear measurement range of all samples ends at a sensor response of about 30% resulting in an increase of the linearly detectable amount with the thickness. Hence, the variation of the thickness of the sensitive layer is a powerful tool to adapt the linear measurement range (proportional to the thickness) as well as the sensitivity (proportional to the inverse thickness) to the application requirements. Calculations combining the sensor model with the measurement results indicate that for operation in the linear range, about 3% of the LNT material is converted to nitrate.