This study on ceramic thermal barrier coatings (TBCs) presents baseline thermal conductivity data on as-deposited 7-8 wt.% YSZ and a paired-cluster rare-earth oxide doped YSZ, prepared using air plasma spray (APS). The thermal diffusivity for each coating was measured up to 1100°C using the laser flash method, and from these values, the thermal conductivity was calculated. The maximum benefit for thermal conductivity reduction in TBCs with a (GdO2, Yb2O3)-doped YSZ composition was highest for APS dense, vertically macrocracked microstructures, whereas in the case of low density APS TBCs, the reduction in conductivity was found to be more strongly influenced by horizontally-oriented, sub-critical defects and porosity within the coating microstructure.

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