Thermophysical properties of Yb2O3 doped Gd2Zr2O7 and thermal cycling durability of (Gd0.9Yb0.1)2Zr2O7/YSZ thermal barrier coatings

(Gd1−xYbx)2Zr2O7 compounds were synthesized by solid reaction. Yb2O3 doped Gd2Zr2O7 exhibited lower thermal conductivities and higher thermal expansion coefficients (TECs) than Gd2Zr2O7. The TECs of (Gd1−xYbx)2Zr2O7 ceramics increased with increasing Yb2O3 contents. (Gd0.9Yb0.1)2Zr2O7 (GYbZ) ceramic exhibited the lowest thermal conductivity among all the ceramics studied, within the range of 0.8–1.1 W/mK (20–1600 °C). The Young's modulus of GYbZ bulk is 265.6 ± 11 GPa. GYbZ/YSZ double-ceramic-layer thermal barrier coatings (TBCs) were prepared by electron beam physical vapor deposition (EB-PVD). The coatings had an average life of more than 3700 cycles during flame shock test with a coating surface temperature of ∼1350 °C. Spallation failure of the TBC occurred by delamination cracking within GYbZ layer, which was a result of high temperature gradient in the GYbZ layer and low fracture toughness of GYbZ material.