A Y2O3 coating was prepared using the atmospheric plasma spraying (APS) technique. On exposing the coating to CF4/O2/Ar plasma, a fluorine contamination layer (YOxFy) was formed, which was the main cause of process drift and contamination particle generation on the APS–Y2O3 coating surface. To remove the YOxFy layer on the coating surface, a piranha solution, which is a mixture of sulfuric acid and hydrogen peroxide, was employed for cleaning. The piranha solution was found to be an excellent medium for removing the YOxFy layer. The amount of contamination particle generated could be reduced by approximately 37% after cleaning with a 3:1 piranha solution compared with before cleaning.

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