Formation of pyrochlore at LSM-YSZ interfaces is studied in the temperature range from 700 to 1250℃ for various LSM and YSZ compositions. At 900℃, small isolated islands are observed to form in the interfacial plane; continuous scales develop only at much higher temperatures. The very irregular distribution in space and size of the pyrochlore islands formed in the temperature range from 900 - 1250℃ reflects high nucleation and growth barriers. Pyrochlore forms more easily for Mn-deficient LSM. For the reaction of LSM with tetragonal 3YSZ, formation of Y,Mn,La-stabilized cubic phase precedes the pyrochlore formation. Single and polycrystalline cubic YSZ exhibit a larger interface coverage than tetragonal YSZ. Intersections of LSM/3YSZ interfaces with 3YSZ grain boundaries are not preferentially decorated with pyrochlore. As a consequence, less pyrochlore is formed for small grain size 3YSZ than for larger size cubic 8YSZ at equivalent reaction conditions.
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