Planar LiSICON-based potentiometric CO2 sensors: influence of the working and reference electrodes relative size on the sensing properties

The feasibility of planar screen-printed CO2 sensors based on LiSICON as ion conductor and on lithium carbonate as auxiliary phase is demonstrated, on the condition that the carbonate melts during the manufacturing process. The addition of calcium or barium carbonate to lithium carbonate in eutectic proportions, suppresses the interference with water vapor. The replacement of both carbonate and gold superposed layers by a unique composite layer serving as working electrode, strongly improves the recovery times. The surface ratio between the working and reference electrodes appears of primary importance in the operating of the sensor and a tentative explanation of the phenomenon is proposed. The performances of sensors optimized on the basis of these results are finally evaluated.