Sintering resistance and phase stability of (Y0.2La0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 for ultra-high temperature thermal barrier coatings

Abstract

High-temperature stability, including sintering resistance and phase stability, is critical for thermal barrier coatings (TBCs) applied at ultra-high temperature over 1500 °C. In this work, we reported a high-entropy rare-earth zirconate (Y02La0.2Nd0.2Sm0.2Eu0.2)2Zr2O7 (YLNSE) synthesized by solid-state reaction method. X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive spectrometer (EDS) mapping results confirmed that YLNSE formed a single-phase pyrochlore structure with uniform rare earth elements distribution. YLNSE maintained more uniform microstructure, higher porosity retention, lower grain growth rate and better thermomechanical properties during sintering at 1500 °C, as the results of the ordered crystal structure and sluggish diffusion effect, indicating a better sintering resistance than conventional TBC material yttria-stabilized zirconia (YSZ). In addition, YLNSE also demonstrated high coefficient of thermal expansion (CTE, 11.04 × 10-6K-1, 25–1500 °C) and low thermal conductivity (1.95 W m-1 K-1, 1500 °C), as well as good phase stability at 1500 °C. In view of the excellent high-temperature stability of YLNSE, it is a promising candidate for ultra-high temperature TBCs.