Dense solid electrolytes based on lanthanum silicate, La10Si6O27 were fabricated and their electrical conducting properties were studied in detail under various atmospheres, including H2O- or D2O-humidified Ar. The family showed almost PO2-independent conductivity, while a slight increase in conductivity with increasing PO2 was observed in the high-temperature region. The ionic transport number evaluated from the O2/Ar oxygen concentration cell was higher than 0.964 at 1073 to 1273K.

Electrical Properties of La10Si6O27-Based Oxides. A.Mineshige, T.Nakao, M.Kobune, T.Yazawa, H.Yoshioka: Solid State Ionics, 2008, 179[21-26], 1009-12