Yttria stabilized zirconia with a composition of ZrO2-8wt%Y2O2 typically serves as the topcoat in thermal barrier coating systems. It has been reported, however, that YSZ with lower yttria content is more resistant to thermal shock and the effects of high-temperature sintering. To investigate these reports, nano-agglomerated 5YSZ and 8YSZ powders were deposited on FeCrAl substrates by atmospheric plasma spraying and the coatings were heat treated at 1400 °C for 1, 5, and 20 h. The nanostructure content in the 5YSZ samples was found to be about 20% higher, the microhardness 11% lower, and the size of unmelted particles about 27% smaller, which shows that bimodal structured 5YSZ has higher sintering resistance than traditionally used 8YSZ.

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