Fig. 1. Schematic and SEM images of the thermal barrier system, showing as-coated samples and samples aged for 200 h at 1000 �C in air. The as-coated sample shows (B) the intercolumnar spacing (ICS) between YSZ columns near the top coat surface and (C) the intermixed, porous (preexisting) TGO. The aged samples show (D) narrowed ICS and rigid connections between the YSZ columns and (E) the bi-layered structure of the TGO. For both as-coated and aged samples, the top coat closest to the TGO does not show expressed ICS between columns.
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