Doped Ceria as a Solid Oxide Electrolyte

Ceria doped with divalent or trivalent cations is a mixed conductor; conduction occurs predominantly by the motion of oxygen vacancies or by electrons, depending on the departure from stoichiometry. In order to establish the electrolytic domain at which behaves primarily as an ionic conductor with transference number , a careful study was made of the conductivity, σ, as a function of temperature and oxygen partial pressure, covering the range of 100;–10−22 atm in small steps. From these data the electrolytic domain was determined; it extends to about 10−13 atm at 600°C. When compared to calcia‐stabilized zirconia (CSZ), doped ceria shows a higher conductivity, lower activation energy (0.76 eV) for anion vacancy migration, and absence of polarization effects to lower temperatures. These results indicate that doped ceria may be an attractive candidate for fuel cells and other applications at temperatures below those at which CSZ is useful.