Influence of Gd doping on the coefficient of thermal expansion and molten CMAS corrosion behavior of (Yb_1-xGd_x)₂SiO₅ceramics

Yb₂SiO₅ is one of the promising candidate materials for thermal/environmental barrier coating. A series of (Yb_1-xGd_x)₂SiO₅ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared using a high-temperature solid-state sintering method. Influence of Gd doping on coefficient of thermal expansion(CTE) and molten CMAS corrosion behavior of Yb₂SiO₅ were investigated. The results showed that all of (Yb_1-xGd_x)₂SiO₅ ceramics were composed of typical single phase Yb₂SiO₅. The average CTE of (Yb_1-xGd_x)₂SiO₅ in the temperature range of 30 °C-1400 °C was (6.70-7.40) × 10⁻⁶ K⁻¹, and average CTE of (Yb_0.8Gd_0.2)₂SiO₅ was the lowest. The phase composition of (Yb_1-xGd_x)₂SiO₅ ceramics after CMAS corrosion at 1250 °C for 2 h/12 h and at 1400 °C for 12 h was Yb₂SiO₅ and Ca₂(Yb,Gd)₈(SiO₄)₆O₂ (Apatite). As temperature increases, the grain size of corrosion products grows. The average corrosion depth of (Yb_0.7Gd_0.3)₂SiO₅ was 10 μm, 12 μm, and 181 μm after exposure at 1250 °C for 2 h/12 h, and 1400 °C for 12 h, respectively. (Yb_0.7Gd_0.3)₂SiO₅ demonstrates excellent resistance to CMAS corrosion. This offers guidance for exploring and optimizing rare earth silicates as candidates for T/EBC materials.