Plasma Sprayed Yb2Si2O7 as an example of rare-earth silicate for environmental barrier coatings application: processing effects on coating features

Rare earth (RE) silicates are envisioned as principal candidates for environmental barrier coatings (EBCs). Among them, Yb₂Si₂O₇ arises as preferred candidate for EBC top coats due to its relative good stability in water vapor atmospheres, single crystalline phase in the whole temperature range and its low reactivity with calcium-magnesium-aluminosilicate (CMAS). The main drawback that RE silicates face is the amorphous nature of the as deposited (Plasma Spray) coatings. Several attempts have been made to get fully crystalline coatings such spraying inside furnaces. This approach, although successful, is unattractive to the industry so other paths must be explored. The present work aims to understand the process – microstructure – property relationships in plasma sprayed Yb₂Si₂O₇ coatings through subjecting the material to a deliberate choice of deposition energies and temperatures, evaluating the crystalline nature (XRD, DTA, CTE), microstructure (SEM) and chemical composition (EDS) of the obtained coatings before and after post-spraying treatments.