Microstructural and electrochemical characterizations of an electrolyte with an apatite structure, La9Sr1Si6O26.5

Abstract The electrochemical properties of dense La 9 Sr 1 Si 6 O 26.5 pellets were studied. High conductivity values were measured (8.8 × 10 − 3  S cm − 1 at 700 °C) for this pure ionic conductor. Semipermeability measurements allowed measuring an electronic transport number of 5 × 10 − 5 at 700 °C under air. These results prove that La 9 Sr 1 Si 6 O 26.5 is a pure ionic conductor. Ageing tests of this compound during one month showed a stable behaviour of the conductivity under air and a slight decrease of it under humidified atmosphere.