Strontium surface segregation in La0.6Sr0.4Co0.2Fe0.8O3 - δ subjected to mechanical stress

The current study investigates Sr surface segregation phenomenon for polycrystalline La0.6Sr0.4Co0.2Fe0.8O3-delta annealed under four-point bending stress to elucidate effects of tensile and compressive stress on the segregation at elevated temperature (1173 K). On the stress-free surface, Sr segregation was mostly observed at the grain boundaries, whereas, on the tensile surface, finer and fewer segregation particles appeared at grain boundaries. For compressive surfaces, the segregation of much smaller and fewer particles was observed at the grain boundaries but also within the grain interiors. The surface segregation was assigned to a Sr-rich phase, possibly SrSO4. The present results indicate that Sr surface segregation could be suppressed by applying mechanical stress, especially compressive stress, which could be explained by a counteraction between Sr migration for surface segregation and creep deformation. (C) 2016 Elsevier B.V. All rights reserved.