Lanthanide co-doped YSZ double-ceramic-layer thermal barrier coatings: Unlocking superior sintering resistance, thermal durability, and insulation for extreme environments

Abstract

The phase instability and poor sintering resistance of conventional 8YSZ limit its use in advanced thermal barrier coatings (TBCs). To overcome these limitations, a novel Gd and Yb co-doped YSZ (RYSZ) powder was developed and used to fabricate the double-ceramic-layer (DCL) RYSZ/8YSZ TBC via atmospheric plasma spraying (APS), which were systematically compared with single-layer RYSZ and 8YSZ TBCs. RYSZ exhibited excellent phase stability, with no transformation after 200 h at 1400 °C, unlike 8YSZ, where m-ZrO₂ phase increased from 0 % to 34.2 %. The DCL TBC showed superior sintering resistance, with porosity reductions of only 29.89 % after 200 h at 1150 °C, compared to 73.94 % for the single-layer 8YSZ TBC. In thermal shock cycling, the DCL TBC remained intact after 60 cycles, outperforming single-layer RYSZ and 8YSZ TBCs, which failed at 35 and 40 cycles, respectively. Additionally, the DCL TBC achieved excellent thermal insulation, with a 313.4 °C temperature drop at 1500 °C. The DCL RYSZ/8YSZ structure emerges as the optimal configuration, combining phase stability, sintering resistance, and thermal durability, paving the way for next-generation TBCs in extreme environments.