Thermal shock behavior of mixed ytterbium disilicates and ytterbium monosilicates composite environmental barrier coatings

The thermal shock properties of mixed Yb2Si2O7 and Yb2SiO5 composite environmental barrier coating (EBC) topcoat, with various Yb2Si2O7-to-Yb2SiO5 ratios, are investigated between room temperature and 1500 degrees C. The results show that, with more Yb2Si2O7 introduced, the mixed Yb2Si2O7 and Yb2SiO5 composite topcoats exhibit an increasing thermal shock property. This may be attributed to that, while Yb2Si2O7 mole fraction increases, the thermal expansion coefficient of the mixed Yb2Si2O7 and Yb2SiO5 composite ceramics becomes smaller, more matched to substrates and the fracture toughness of the mixed Yb2Si2O7 and Yb2SiO5 composite ceramics becomes larger, both of which are favoring the improvement of thermal shock resistance.