Protonic conduction in La2Zr2O7-based pyrochlore materials

Electrochemical pumping of oxygen can be used to adjust the oxygen partial pressure without changing the total content of hydrogen containing species (H-2 + H2O), and this is suitable for studying materials with proton conductivity selectively dependent on water vapour partial pressure. This method was used to demonstrate that lanthanum zirconate based materials possess a significant protonic conductivity contribution at temperatures lower than about 1000 degrees C, and to revise the defect chemistry model. Y for Zr substitution enhances the electron hole, oxygen ion and protonic conductivity contributions, as expected for addition of an acceptor species. The effective mobility of oxygen vacancies, and the equilibrium constant for formation of anti-Frenkel defects were evaluated by taking into account the oxygen ion conductivities in Y-containing and undoped lanthanum zirconate.