Oxygen surface exchange and diffusion in LaGaO3 based perovskite type oxides

Isotopic exchange was used to determine the oxygen tracer diffusion coeffic ient and surface exchange coefficient of LaGaO3 based perovskites at a temp erature from 923 to 1173 K. The oxygen diffusion coefficient was found to b e higher than the surface exchange coefficient. In addition, the change in activation energy of the surface exchange coefficient was also observed at 973 K. The results indicate that the oxygen exchange behavior of acceptor d oped LaGaO3 is similar to that of other oxygen ion conductors such as ZrO2- Y2O3 and CeO2-Gd2O3, rather than that was found for the isostructural, but mainly mixed conducting, perovskite oxides. It was noted that the diffusion coefficient was not influenced while the surface exchange coefficient was strongly affected by the oxygen partial pressure of isotopic exchange and t he empirical relation was found to be a power of 0.45. Oxygen tracer diffus ion data obtained by SIMS was compared to that obtained by the measurement of the electrical conductivity with the Nernst-Einstein relationship. For t he temperatures at which the measurements were taken, the two were almost i dentical within the accuracy of SIMS, strongly indicating that the conducti vity in LSGM is ionic. The high oxide ion conductivity in LSGM results from the high mobility of oxygen vacancies in addition to the high concentratio n of oxygen vacancies. (C) 1998 Published by Elsevier Science BN. All right s reserved.