Phase evolution, thermophysical and mechanical properties of high-entropy (Ce0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 ceramic for advanced thermal barrier coatings

Single-phase high-entropy rare-earth zirconate (Ce0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 with large thermal expansion coefficient (11.69 x10-6 K-1, 25-1500 degrees C), low thermal conductivity (1.07 W m-1 K-1, 1500 degrees C), and high fracture toughness (1.84 +/- 0.03 MPa m1/2, 25 degrees C) was successfully synthesized using reverse coprecipitation and high-temperature calcination. The underlying mechanism governing the observed results was analyzed by considering the ionic bond strength, crystal lattice energy, and bond length. X-ray diffraction and Raman spectroscopy results demonstrated that the pyrochlore structured sample has excellent high-temperature phase stability. Moreover, after being heated at 1600 degrees C for 10-30 h, the average grain size of this sample only in-creases from 0.95 mu m to 1.47 mu m, indicating a sluggish grain growth rate. The outstanding combination of thermophysical and mechanical properties of the (Ce0.2Nd0.2Sm0.2Eu0.2Yb0.2)2Zr2O7 emphasizes its enormous potential for next-generation thermal barrier coating applications.