A CO2 gas sensor based upon composite Nasicon/Sr–β–Al2O3 bielectrolyte

A novel tube shape CO2 gas sensor based upon interfacing two composite solid electrolytes-Nasicon/glass and Sr–β–Al2O3/YSZ with a BaCO3/Na2CO3 (4:6) auxiliary electrode has been investigated. In the sensor, Nasicon/glass is melted in Sr–β–Al2O3/YSZ tube, BaCO3/Na2CO3 (4:6) placed on top surface of Nasicon/glass as auxiliary electrode and Pt coating on outer surface of Sr–β–Al2O3/YSZ tube as reference electrode. The experimental results have shown that the sensor has excellent sensing performance. The relationship between emf of the sensor and logarithm of partial pressure of CO2 is linear over a concentration range of 12–10,000 ppm at a fixed temperature. The oxygen content in mixture gas does not affect response signals of the sensor. Up to 100 ppm NO2 does not change sensor performance. SO2 is a serious interference gas due to its reaction with electrolyte and carbonates sensing electrode. The tolerable limit of the CO2 sensor to SO2 was 1.7 ppm.