Investigation of CO2 sensor based on NASICON synthesized by a new sol–gel process

A small volume tube-type CO2 sensor was fabricated, which was based on the solid electrolyte material of NASICON prepared by using inorganic salt as raw material. As a sol–gel process was employed, the synthesizing temperature and time were reduced to 800 °C and 8 h, respectively. The resulted NASICON was characterized by XRD, IR, TEM and ion conductivity measurement. Within a wide range of CO2 volume ratio concentration from 100 to 10,000 ppm, the output electromotive force (EMF) of the sensor followed Nernst equation well, and its response and recovery time were less than 15 and 28 s, respectively. The experiments indicated that there was little influence on the sensor characteristics from water vapor, CH4 and CO, which could be attributed to the choice of the suitable binary carbonate electrode and the use of the active carbon cap in package.