Sintering resistance and phase stability of high-entropy (Y_0.2La_0.2Nd_0.2Sm_0.2Eu_0.2)₂Zr₂O₇ thermal barrier coatings at 1500 °C

High-entropy (Y_0.2La_0.2Nd_0.2Sm_0.2Eu_0.2)₂Zr₂O₇ (YLNSE) has been verified as a potential thermal barrier coating (TBC) material. In this work, the YLNSE coatings were first prepared by plasma spray-physical vapor deposition (PS-PVD) technique. The sintering resistance and phase stability of the YLNSE coatings at 1500 °C were investigated and compared to the referential gadolinium zirconate (GZO) coatings. It was found that the as-sprayed YLNSE and GZO coatings had a typical PS-PVD feather-like columnar structure and were composed of the defective fluorite phases. At 1500 °C, the microstructures and mechanical properties of the two coatings evolved during the sintering process, showing a general trend of significant change in the early stage and stabilization in the later stage. Compared with the GZO coatings, the sintering resistance of the YLSNE coatings was improved, maintaining smaller grain size, higher porosity and lower Young's modulus throughout the process. Furthermore, the YLNSE coatings exhibited better phase stability than the GZO coatings at 1500 °C. This work demonstrated the feasibility of high-entropy rare-earth zirconates (HE-REZ) TBCs with high strain tolerant structure and deepened the understanding of high-temperature stability in terms of microstructure, mechanical property, as well as phase composition. Besides, these findings provided a solid foundation for the application of strain tolerant HE-REZ TBCs in advanced aero-engines.