Abstract:Ytterbium silicate is an important material for environmental barrier coatings (EBC). In this paper, ytterbium silicate coatings were prepared by plasma spraying processes. The coatings were subjected to thermal shock tests under different conditions including gas-burning testing and water-vapor-burning testing with calcium ion. The microstructure evolution behavior of coatings subjected to the tests was studied. The results showed that the phase transformation from ytterbium disilicate to ytterbium monosilicate easily occurred at high temperatures, which may be due to the reaction between the material and water vapor. In the hot gas environment at 1350 ℃ , obvious sintering phenomenon occurred on the surface layer of the coating. Under the water-vapor-burning condition (heating temperature 1250 ℃ ) which contained calcium ion, the surface layer of the ytterbium silicate coating showed bubbling characteristics and was subjected to calcium ion corrosion. Possible chemical reaction mechanisms as provided for the microstructure evolution of the coatings.