Characterization of lanthanum zirconate formation at the A-site-deficient strontium-doped lanthanum manganite cathode/yttrium-stabilized zirconia electrolyte interface of solid oxide fuel cells

Lanthanum zirconate (LZO) formation and growth kinetics between 1273-1673 K at the A-site (La, Sr)-deficient Sr-doped lanthanum manganite (LSM)/yttrium-stabilized zirconia (YSZ) interface were studied using high-resolution transmission electron microscopy-energy-dispersive X-ray spectrometry (HRTEM-EDS). A cross-section TEM sample preparation technique was developed using a dual-beam focused ion beam and an in situ Omniprobe manipulator. The LZO pyrochlore phase was identified at the LSM/YSZ interface by TEM. The LZO is epitaxial with respect to the YSZ phase but not to the LSM phase. EDS results coupled with structural analysis suggest that La diffusion is a critical step in LZO formation. This study shows that LZO formation can occur even for A-site-deficient LSM with a La composition of 78 mol% (< 86 mol%). The activation energy for LZO formation was found to be 168 +/- 8 KJ/mol.