CO2 gas sensor using lithium ionic conductor with inside heater

The raw material for lithium ionic conductor (Li1+xZr2SixP3-xO12, where x i s about 2) was synthesized by sol-gel method. Eutectic mixture (Li2CO3:K2CO 3:Na2CO3 = 47.0:25.6:27.4 wt.%) was formed on the sensing electrode as an a uxiliary material. For the wide range of CO2 concentration from 1000 to 10, 000 ppm, the emf examined at 420 degrees C showed excellent agreement with theoretical value of a Nernst's equation. The 90% response time was as shor t 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 investig ated for 60 days. (C) 2000 Elsevier Science S.A. All rights reserved.