Novel Non‐Equimolar High‐Entropy Zirconates With Superior Thermophysical Properties

ABSTRACT Rare‐earth zirconates (RE 2 Zr 2 O 7 ) are promising candidates for topcoat materials in thermal barrier coatings (TBCs). However, their practical application in TBCs is limited by poor fracture toughness and low thermal expansion coefficient (TEC). To address these challenges, three novel nonequimolar high‐entropy zirconates (HEZs), that is, (Nd 3/16 Sm 3/16 Eu 3/16 Gd 3/16 Me 1/4 ) 2 Zr 2 O 7 (Me = La, Pr, Ce, defined as NSEGL, NSEGP, NSEGC, respectively), are successfully synthesized. Among them, NSEGP has the largest fracture toughness (3.32 MPa m 1/2 ), which is 2–3 times higher than that of the single component. Simultaneously, all three samples exhibit both lower thermal conductivity (1.62–1.90 W m −1 K −1 at 1273 K) and higher TEC (11.67–12.22 × 10 −6 K −1 ) than those of YSZ and most other reported topcoat materials for TBCs. Additionally, NSEGC exhibits the highest Vickers hardness (9.86 GPa) and Young's modulus (265 GPa), which is attributed to its strongest bond strength originating from enhanced Zr‐O 48f bonds. All three samples possess excellent high‐temperature phase stability, oxidation resistance and chemical compatibility with α‐Al 2 O 3 . Given their overall performance, these three HEZs show great promise as topcoat materials for TBCs.