Li₂CO₃-La_9.33Si₆O₂₆を検知極に用いた固体電解質型炭酸ガスセンサー

抄録

Recently NASICON (Na₃Zr₂Si₂PO₁₂) has been used as the solid electrolyte for EMF (electromotive force) CO₂ sensors. However, it has been difficult to obtain a sufficiently high quality of this type of sensor. In general, when the EMF CO₂ sensor is exposed to a high-humidity atmosphere, the EMF of the sensor decreases to less than two-thirds of its initial value. For the purpose of improving the humidity resistance of the sensor, the reason for the decrease of the EMF sensor after exposure to a high-humidity atmosphere is investigated, and an appropriate counterplan is devised. In this report, Li₂CO₃, Li₂CO₃-La₂O₃, and Li₂CO₃-La_9.33Si₆O₂₆ are adopted as materials for the sensing electrodes. Li₂CO₃ reacts with NASICON and forms friable compounds when these materials are exposed to an atmosphere of 90% relative humidity at 60°C. In contrast, Li₂CO₃-La_9.33Si₆O₂₆ is the material most resistant to humidity, because La_9.33Si₆O₂₆ prevents the reaction between NASICON and Li₂CO₃.