High-Temperature Sintering Behavior of Gd2O3-Yb2O3 Co-doped 8YSZ Ceramic for Thermal Barrier Coatings

Multivariate rare-earth co-doped zirconia is one of the candidate materials for ultra-high-temperature thermal barrier coatings. GdYb-8YSZ (90ZrO2-4Y2O3-3Gd2O3-3Yb2O3, mol.%) nanopowder and its bulk ceramic were successfully fabricated. Microstructure, thermal conductivity and sintering behavior of GdYb-8YSZ ceramic at 1400 °C were investigated. The results showed that GdYb-8YSZ nanopowder was composed of a single c-ZrO2 phase with the particle size in the range of 20-40 nm. The thermal conductivity of GdYb-8YSZ does not change much with temperature, in the range of 1.31-1.74 W m−1 K−1 from room temperature to 1400 °C. This is mainly due to the coupling effect of oxygen vacancy defects, lattice distortion and photon heat conduction. However, the grain size of GdYb-8YSZ ceramic gradually increased from 1.43 in the as-prepared state to 3.44 μm after 96 h sintering, and GdYb-8YSZ had good high-temperature phase stability and poor sintering resistance at 1400 °C.