FEASIBILITY OF A POTENTIOMETRIC CO2 SENSOR-BASED ON NA-BETA-ALUMINA IN THE LIGHT OF THE ELECTRONIC CONDUCTIVITY OF THE ELECTROLYTE

The sodium activities occurring at the measuring electrode of a CO2 se nsor with an Na2CO3 sensitive layer are compared with the data known s o far on the electronic conductivity of the Na-beta-alumina electrolyt e. This comparison indicates that the sodium potential of the measurin g electrode is far away from the electrolytic domain of the electrolyt e by several orders of magnitude. Therefore, the measurement of both v ery high contents and minute traces of CO2 in air should be impossible by means of such a sensor. Since this is in contradiction to general practical experience, the conclusion must be drawn that the so-far pub lished data on the p-conductivity of Na-beta-alumina are probably erro neous. However, it has to be assumed that the behaviour of a CO2 senso r will be affected, possibly considerably, by electronic transference in the electrolyte. This throws new light upon the feasibility of a CO 2 sensor and the understanding of its behaviour.