Effects of grain-boundary diffusions and modifications on the electrical conductivities of YSZ coatings with columnar microstructure

• Electrical conductivity of YSZ coating is modified by G.B. elemental diffusions.
• Conductivity of Fe-modified coating is 6 times higher than that of the as-deposited.
• Scavenging effects of Fe2O3 on intergranular Si-phase are verified in YSZ coating.
• A segregation of Fe and Si into triple grain junctions is confirmed in YSZ coating.
• Conductivity of Si-modified YSZ coating is 3 times lower than that of as-deposited.

The YSZ coatings with nanocrystalline columnar structure were prepared by magnetron sputtering and then dip-coated by a Fe-containing sol. The elements from sol decomposition products were diffused at 600 °C for 2 h to modify the columnar grain boundaries. The electrical conductivities of Fe-modified YSZ coating are predominantly ionic and 6–7 times higher than those of the as-deposited coating. The electrical conductivity increment is explained on the scavenging effects of diffused Fe2O3 on the intergranular siliceous phase based on the fact that a strong segregation of Fe and Si into the triple grain junctions is verified by EDS analysis.