Phase stability, sintering, and thermal conductivity of plasma-sprayed ZrO2–Gd2O3 compositions for potential thermal barrier coating applications

Structural changes resulting from sintering and phase transformation limit the high-temperature durability of ZrO2-based thermal barrier coatings (TBCs). The objective of this study was to investigate the use of Gd2O3 as a stabilizer for ZrO2-based TBC compositions. The influence of Gd2O3 concentration (4–20 mol.%) on the sintering and phase stability of plasma-sprayed ZrO2 powders was investigated and the data were compared with those for the state-of-the-art Y2O3-stabilized ZrO2. At an equivalent concentration (4 mol.%), Gd2O3-stabilized ZrO2 sintered more slowly but had a lower resistance to destabilization of the metastable tetragonal (t′) phase, when compared to Y2O3-stabilized ZrO2. The thermal conductivity of Gd2O3-stabilized ZrO2 was lower than that of Y2O3-stabilized ZrO2. Factors influencing the sintering and phase transformation of plasma-sprayed Gd2O3-stabilized ZrO2 are discussed.