Microstructure, thermal characteristics, and thermal cycling behavior of the ternary rare earth oxides (La2O3, Gd2O3, and Yb2O3) co-doped YSZ coatings

In this paper, La2O3, Gd2O3, and Yb2O3 co-doped yttria stabilized zirconia (LGYYSZ) thermal barrier coatings were prepared on a nickel-based superalloy by atmospheric plasma spraying. The phase stability, coefficient of thermal expansion (GTE), and thermal conductivity of the LGYYSZ and YSZ coatings were measured. Thermal cycling at 1400 degrees C was implemented to evaluate the feasibility of LGYYSZ as an optimal ceramic material for thermal barrier coatings (TBCs) of next-generation gas turbines. The results show that the LGYYSZ coating exhibits a stable cubic phase, even after annealing at 1500 degrees C for 100 h. The CTE of LGYYSZ is slightly higher than that of YSZ. The thermal conductivity of the LGYYSZ coating at 1400 degrees C is 1.08 Wm(-1).K-1, which is similar to 26.5% lower than that of YSZ. The thermal cycling lifetime of the LGYYSZ coating at 1400 degrees C is 468 cycles, which is similar to 2.7 times that of the YSZ coating. The longer thermal cycling life of the LGYYSZ TBC can be attributed to the excellent phase stability and lower thermal conductivity.