Composition Optimization, High-temperature Stability and Thermal Cycling Performance of Sc-doped Gd2Zr2O7 Thermal Barrier Coatings: Theoretical and Experimental Studies

Abstract Sc was doped into Gd 2 Zr 2 O 7 for expanding the potential for thermal barrier coating (TBC) applications. According to first-principles calculation, the solid solution mechanism of Sc in Gd 2 Zr 2 O 7 lattice was revealed, i.e., Sc first occupies the lattice interstitial sites followed by substituting for Gd, and the interstitial Sc concentration is less than 11.11%. By considering the mechanical and thermophysical properties comprehensively, the optimum Sc doping content was determined to be 16.67%, and this composition was selected to produce TBCs by air plasma spraying with YSZ as a bottom ceramic coating (Gd-Sc/YSZ TBC). After sintering at 1400 ℃ for 100 h, Gd-Sc coatings remain phase and structural stability indicative of excellent sintering resistance. By thermal cycling tests, Gd-Sc TBCs fails due to the low toughness and the interface reaction between Gd-Sc and boding coatings, while Gd-Sc/YSZ TBCs exhibit much longer thermal cycling lifetime, and the failure mode is YSZ coating cracking.