Origin of cathodic degradation and new phase formation at the La0.9Sr0.1MnO3/YSZ interface

Abstract New phase formation at the La 0.9 Sr 0.1 MnO 3 /YSZ interface and its effects on the cathodic performances were studied at 900 °C in air. The resistance caused by the interfacial product layer kept increasing with time to reach up to 40% of the total resistance after 500 h. The interfacial product was identified as La 2 Zr 2 O 7 by XRD measurement. The electrical conductivity of La 2 Zr 2 O 7 (2.4 × 10 −5 S cm −1 at 1000 °C), measured by AC impedance and current interruption methods, was 4 to 7 orders of magnitude smaller than those of La 0.9 Sr 0.1 MnO 3 electrode or YSZ electrolyte. Either the electronic conductivity or the electrochemical O 2 reduction activity of La 2 Zr 2 O 7 was negligible. Combining these results, a conclusion was made that the cathodic degradation comes mainly from the growth of interfacial product layer and its contribution to the cell resistance increment is ohmic in nature.