Abstract: A type of CO2 sensor based on oxygen concentration cell was designed as following: Cell I: Pt | Au, O2, CO2| Na2CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt or Cell II: Pt | Au, O2, CO2|K2$CO3(Au)|NKBA(Au)|YSZ|O2, CO2|Pt. (Na, K-β/β''-Al2O3 is named by NKBA). The sensor signal is consistent with the Nernstian slope within the region of phase equilibrium for Na, K-β/β''-Al2O3 material. The relationship between CO2 sensor voltage response and phase equilibrium of solid electrolyte Na, K-β/β''-Al2O3 is discussed in this paper.

Key words: CO2 sensor, Phase equilibrium, Solid electrolyte, Na, K-β/β''-Al2O3