NiO-Li_2CO_3検知極とLi_2TiSiO_5を用いた炭酸ガスセンサー

概要

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Sodium ionic conductors such as NASICON (Na_3Zr_2Si_2PO_<12>) have been used as a solid electrolyte for electromotive force (EMF) CO_2 sensor. However, it has been difficult to obtain a sufficiently high quality for this type of sensor. In general, when the EMF CO_2 senser is left in an atmosphere having a high water concentration, such as a high-humidity atmosphere or condensation atmosphere, the EMF of the sensor greatly decreases. For the purpose of improving the humidity-resistance of the CO_2 sensor, Li_2TiSiO_5 is employed as a solid electrolyte. It is composed of the following electrochemical cell: CO_2-Air/Au-Li_2CO_3/Li_2TiSiO_5/Au/CO_2-Air. The electrochemical reaction is in good agreement with the Nernst equation, and reacted electron is calculated as 2.04. The sensor fabricated with Li_2TiSiO_5 shows good linearity when it is exposed to an atmosphere of 90% relative humidity at 60℃. However, the EMF of the sensor decreases slightly as compared to its initial value. In order to obtain a high humidity-resistance for the sensor, NiO-Li_2CO_3 is used as the sensing electrode. In this case, the reaction constant, 2.04, is preserved and the EMF of the sensor does not change after exposure to high humidity atmosphere. Au-NiO-Li_2CO_3/Li_2TiSiO_5/Au can be considered to serve as a high humidity-resisting system for solid electrolyte CO_2 sensors. [Received June 10, 2003; Accepted August 29, 2003]
2003-11-01