Configurational entropy–driven tuning of thermomechanical properties in pyrochlore rare-earth zirconates for thermal barrier coatings

High-entropy rare-earth zirconates (RE 2 Zr 2 O 7 ) have attracted considerable attention as thermal barrier coatings (TBCs) candidates. In this study, pyrochlore RE 2 Zr 2 O 7 (RE = Nd, Sm, Eu, Gd, Dy) ceramics were synthesized with a fixed average RE 3+ radius while varying configurational entropy by tuning the number of principal cations. The ceramics were synthesized and systematically examined to assess the effect of entropy on thermo-mechanical properties. With increasing entropy, the thermal conductivity and the coefficients of thermal expansion of the entropy engineering designed RE 2 Zr 2 O 7 are improved, attributable to enhanced anharmonicity from elemental mixing, which leads to lattice distortion and a high density of dislocations. These features intensify phonon scattering and strengthen the Grüneisen response. Fracture toughness is also enhanced owing to increased energy dissipation during crack propagation via dislocation interactions. This work highlights configurational entropy engineering as a general route to tune thermo-mechanical properties for promising TBC top coat candidates.