Effect of microstructure evolution and crystal structure on thermal properties for plasma-sprayed RE2SiO5 (RE = Gd, Y, Er) environmental barrier coatings

In this work, the microstructure evolution, thermal expansion, thermal conductivity, and thermal shock resistance properties of the plasma-sprayed X1-Gd2SiO5, X2-Y2SiO5, and X2-Er2SiO5 coatings were evaluated and compared by experimental measurement and theoretical exploration. Results showed that significant microstructure evolution such as crystallization of amorphous phase, grain growth, and defects reduction was observed in the RE2SiO5 coatings after thermal aging at 1400 °C. The X1-Gd2SiO5 coating exhibited higher CTE values than the X2-Y2SiO5 and X2-Er2SiO5 coatings, which was related to their crystal structure. The thermal conductivity of thermal-aged RE2SiO5 coating was much higher than that of the as-sprayed RE2SiO5 coating, and thermal conductivity was determined not only by crystal structure but also mainly by the microstructure of the coatings. The X2-Y2SiO5 and X2-Er2SiO5 coatings with lower thermal mismatch stresses presented much better thermal shock resistance than the X1-Gd2SiO5 coating.