Potentiometric solid-state CO2 sensor and the role of electronic conductivity of the electrolyte

Recently, the oxygen potential dependence of the signal of a potentiometric CO2 sensor, based on a cation conductor with carbonate as gas sensitive layer, has been interpreted as caused by electronic transference through the electrolyte. Though this interpretation is quite correct, the relationships on the basis of which the effect of electronic conductivity has been discussed are wrong and so are the conclusions on the electronic conduction parameter of the electrolyte material under consideration, i.e. of the lithium ion conductor Li3PO4 + SiO2 (5 mol%). In what follows, the questionable points will be corrected and the role of the electronic conductivity for the understanding of the behaviour of a CO2 sensor will be re-examined.