CO2 gas sensor using lithium ionic conductor with inside heater

The raw material for lithium ionic conductor (Li1+xZr2SixP3−xO12, where x is about 2) was synthesized by sol–gel method. Eutectic mixture (Li2CO3:K2CO3:Na2CO3=47.0:25.6:27.4 wt.%) was formed on the sensing electrode as an auxiliary material. For the wide range of CO2 concentration from 1000 to 10,000 ppm, the emf examined at 420°C showed excellent agreement with theoretical value of a Nernstʹs equation. The 90% response time was as short as 15–20 s. In 40–90% relative humidity, the emf slope of sensor for CO2 gas was 64–67 mV/decade. The long-term stability of the sensor was investigated for 60 days.