Influence of Gd doping on mechanical properties, thermal conductivity and microstructural evolution of (Yb1-Gd )2SiO5 ceramics

Yb 2 SiO 5 is one of the most potential candidate materials for thermal/environmental barrier coating (T/EBC). In order to further reduce its thermal conductivity and improve its mechanical properties, a series of Gd doped Yb 2 SiO 5 [(Yb 1- x Gd x ) 2 SiO 5 ] ceramics were prepared. The effects of Gd doping on the phase composition, mechanical properties, thermal conductivity and microstructural evolution of Gd doped Yb 2 SiO 5 were investigated. The results showed that (Yb 1- x Gd x ) 2 SiO 5 still maintained a single Yb 2 SiO 5 phase. The average fracture toughness of (Yb 1- x Gd x ) 2 SiO 5 ceramics first decreased and then increased in the investigated Gd-doped Yb 2 SiO 5 samples. (Yb 0.9 Gd 0.1 ) 2 SiO 5 had the highest fracture toughness (2.56 MPa m 1/2 ), which was about 30 % higher than that of pure Yb 2 SiO 5 . Thermal conductivity of (Yb 0.9 Gd 0.1 ) 2 SiO 5 ceramic (1.47 W m −1 K −1 at 1200 °C) was about 15 % lower than that of pure Yb 2 SiO 5 . (Yb 1- x Gd x ) 2 SiO 5 ( x ≤ 0.4) had good phase stability after sintering at 1550 °C for 100 h. However, a small amount of Gd 9.33 (SiO 4 ) 6 O 2 and Yb 2 Si 2 O 7 two new phases were generated besides Yb 2 SiO 5 phase in the sintered (Yb 0.5 Gd 0.5 ) 2 SiO 5 . Taken together, (Yb 0.9 Gd 0.1 ) 2 SiO 5 ceramic material will be one of potential candidates for T/EBC.