Solid-state electrochemical CO sub(2) sensor by coupling lithium ion conductor (Li sub(2)CO sub(3)-Li sub(3)PO sub(4)-Al sub(2)O sub(3)) with oxide ion-electron mixed conductor (La sub(0.9)Sr sub(0.1)MnO sub(3))

A solid-state electrochemical cell of the type O sub(2)(air), Pt /La sub(0.9)Sr sub(0.1)MnO sub(3)/Li sub(2)CO sub(3)(+5 mol% Li sub(3)PO sub(4)+6 mol% Al sub(2)O sub(3))/Au, CO sub(2), O sub(2) was composed to determine CO sub(2) concentration, where Li sub(2)CO sub(3), a lithium ion conductor, was used as an electrolyte, and the perovskite-type oxide (La sub(0.9)Sr sub(0.1)MnO sub(3))/O sub(2)-electrode as a reference electrode. The electromotive force (EMF) of the cell was found to be proportional to the logarithm of CO sub(2) partial pressure in CO sub(2) /O sub(2)/N sub(2) gas mixtures at temperatures between 300 and 400 degree C. The EMF responded to changes of CO sub(2) partial pressure within 1 min at 400 degree C. The sensitivity to CO sub(2) of this cell was not affected by coexistence of O sub(2), and the EMF remained constant after the first 15 days. The mechanism for sensing CO sub(2) is discussed.