Development of NOx and CO_2 gas sensor for on-site real-time monitoring

1.现场实时监测利用研制的固体电解质型传感器对CO_2和NO_2进行了现场实时监测。在CO_2监测方面，能够监测教室内CO_2浓度的24小时变化，由于操作油风扇加热器和通风，室内CO_2浓度迅速增加或减少。2.水相/固体电解质界面结构对于Li_2CO_3/MSZ CO_2传感器，证明Li_2ZrO_3界面化合物起离子桥作用，电动势是由Li_2ZrO_3与CO_2反应产生。在Li_2CO_3-BaCO_3（或Li_2CO_3-CaCO_3）/NASICON中，发现BaZrO_3（或CaZrO_3）在NASICON内部形成，其厚度和结构取决于碳酸盐组成。这些界面化合物与传感器的低温敏感性能密切相关。实用传感器的设计实用传感器应尽可能紧凑。在这方面，有必要设计不需要特定参考气体的非分离型固体电解质装置。幸运的是，这里开发的设备本质上适合这种设计。Li_2CO_3/MSZ和Li_2CO_3-CaCO_3/NASICON的CO_2传感器可分别制成平面型和探针型，电流型NO_2传感器也是探针型。

1. On-site real-time monitoring This test was carried out for CO_2 and NO_2 by using the respective solid electrolyte type sensing devices developed. As far CO_2 monitoring, capability of monitoring variations of CO_2 concentration in a school room over 24 hours, a rapid increase or decrease of indoor CO_2 concentration due to operating oil fan heater and ventilating.2.Interface structure of auxiliaty phase/solid electrolyte For the CO_2 sensing device using Li_2CO_3/MSZ,it was proven that an interfacial compound of Li_2ZrO_3 acts as an ionic bridge and that EMF is generated through a reaction between Li_2ZrO_3 and CO_2. In the case of Li_2CO_3-BaCO_3(or Li_2CO_3-CaCO_3)/NASICON,BaZrO_3 (or CaZrO_3) was found to form inside NASICON,its thickness and structure depending on the carbonate compositions used. It was suggested that these interfacial compounds have deep relevance to the lower temperature sensing capability.Design for practical sensors Practical sensors should be as compact as possible. In this respect, it is necessary to design non-separate-type solid electrolyte devices which don't need particular reference gases. Fortunately, the devices developed here were suited to such design intrinsically. The CO_2 sensor using Li_2CO_3/MSZ and Li_2CO_3-CaCO_3/NASICON could be fabricated into a planar type and a probe type, respectively.The amperometric NO_2 sensor was also a probe type.