Effect of Yb2SiO5 addition on the physical and mechanical properties of sintered mullite ceramic as an environmental barrier coating material

In this study, ytterbium monosilicate (Yb2SiO5)-added sintered mullite ceramics are prepared as candidate materials for environmental barrier coatings (EBCs). The effect of adding Yb2SiO5 on the physical and mechanical properties of the sintered mullite ceramics is investigated. The Yb2O3–SiO2–Al2O3 ternary phase diagram indicates that adding Yb2SiO5 to the mullite goes beyond simply mixing; instead, liquid sintering occurs. Therefore, when we add Yb2SiO5 to the mullite, the sintered body possesses a denser microstructure and faster densification rate than does pure mullite. The density rapidly increases with the addition of 6 wt% Yb2SiO5 in the mullite, and almost full densifications are achieved with the addition of 12 wt% and 18 wt% Yb2SiO5. In this study, mullite ceramic that contains 12 wt% Yb2SiO5 exhibits the smallest plastic deformation and the highest elastic modulus among ceramics containing 6, 12, and 18 wt% Yb2SiO5, according to Hertzian indentation results. The results suggest that 12 wt% Yb2SiO5-doped mullite may be expected to act as a potential EBC material based on its excellent elastic properties, dense microstructure, and appropriate coefficient of thermal expansion.