A novel carbon dioxide gas sensor based on solid bielectrolyte

A planar bielectrolyte type of CO2 gas sensor based on Nasicon and Naβ-alumina solid electrolyte pellets with BaCO3–Na2CO3 (weight ratio 44:56) as the auxiliary phase was fabricated. The sensor had good response to CO2 over a wide range covering 6 ppm to 100%. The Nasicon/Pt interface was sensitive to oxygen, while auxiliary phase applied at low temperature on the sodium rich Naβ-alumina was stable against decomposition. In this mode, both electrodes are exposed to the same test gas eliminating the need for a separate reference compartment and O2 concentration does not affect cell EMF. Interface between Nasicon and Naβ-alumina was studied by SEM and EDAX. Diffusion bonding between the two solid electrolytes results in phase change, which affects the electrical properties of electrolyte system.