Influence of alumina impurities on microstructure of LSM–CeO2 composites

A two-phase model composite of LSM–CeO2 was developed to simulate triple phase boundaries of SOFC and to study the impact of alumina impurities on the microstructure. Interfaces between cerium oxide and 10 at.% strontium-doped lanthanum manganite (LSM) were characterized using X-ray diffraction, atomic-force microscopy, focused ion beam milling, field-emission scanning electron microscopy, X-ray energy dispersive spectroscopy and transmission electron microscopy. LSM, which is synthesized by conventional mechanical milling, is found to be doped with alumina from the grinding balls. When LSM powder is mixed with CeO2 and sintered at 1400 °C for 4 h, manganese aluminate spinel, MnAl2O4 and Mn2AlO4, forms at LSM/LSM, LSM/CeO2 and CeO2/CeO2 boundaries. The influence of (Mn,Al)3O4 phase on the mechanical integrity and performance of the cells is discussed.

Research highlights
► This study reports impurity phase formation at interfaces between LSM and CeO2.
► The ball milling produces Al3+ doped LSM and Al2O3–LSM two-phase materials.
► Al2O3 reacts with Mn+ to form (Mn,Al)3O4 at the interfaces of LSM/LSM, LSM/CeO2.
► The impurity phases were characterized by SEM, AFM, TEM and STEM-XEDS.
► The formation of Mn–Al phases at TPBs will impact SOFC stability and performance.