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Inspired by the high entropy effects of high-entropy components, a novel high-entropy rare-earth zirconate (La 1/5 Gd 1/5 Y 1/5 Sm 1/5 Yb 1/5) 2 Zr 2 O 7 (HEC-LZ) was designed and successfully synthesized in this work. In addition, two binary rare-earth doped zirconates (RE-LZ), (La 1/3 Sm 1/3 Yb 1/3) 2 Zr 2 O 7 (LSYZ) and (La 1/3 Gd 1/3 Y 1/3) 2 Zr 2 O 7 (LGYZ), were proposed using the same rare-earth elements for comparison. The thermal barrier coatings with LZ-based ceramic top layer were prepared by spray granulation, solid-phase synthesis and atmospheric plasma spraying techniques. The as-synthesized LZ-based ceramics are all dominated by the pyrochlore phase. Under 1000 °C, the thermal cycling performances of the three coatings were studied. The microstructure evolution and crack expansion during the failure process were investigated in detail. The strengthening mechanism and the cause of coating spallation are proposed in combination with mechanical properties and thermal matching analysis. The results showed that compared with the undoped LZ coating, the thermal shock life of LGYZ coating, LSYZ coating and HEC-LZ coating is improved by nearly 46%, 27% and 57%, respectively. Due to the characteristics of high randomness, HEC-LZ ceramic has a large lattice distortion than RE-LZ ceramics, resulting in a higher coefficient of thermal expansion and fracture toughness, which contributes to maintaining the structure stability of coatings under thermal stress. [ABSTRACT FROM AUTHOR]

Lanthanum zirconate coatings (La 2 Zr 2 O 7 , LZ) have a high Poisson's ratio and low fracture toughness, making it indescribable for long service life at high temperatures. Rare earth doped lanthanum zirconate (RE-LZ) is an effective way to improve its mechanical properties. In this study, the lanthanum zirconate ceramic coating modified by binary rare earth ((La 1/3 Gd 1/3 Y 1/3) 2 Zr 2 O 7 , LGYZ; and (La 1/3 Sm 1/3 Yb 1/3) 2 Zr 2 O 7 , LGYZ) and multi-principal rare earth modified ((La 1/5 Gd 1/5 Y 1/5 Sm 1/5 Yb 1/5) 2 Zr 2 O 7 , HEC-LZ) was studied, aiming to improve the intrinsic mechanical properties of lanthanum zirconate ceramic coating. By comparing the mechanical properties such as fracture toughness, bonding strength, microhardness dissipation parameter, and solid erosion properties of various types of coatings, the results show that compared with binary rare earth modified coatings such as LGYZ and LSYZ, the elastic modulus of the HEC-LZ ceramic coating is reduced by 4.7–6.3%, the microhardness dissipation parameter (MDP) is increased by 4.8–10.2%, and the fracture toughness is increased by 5.2–7.4%. The HEC-LZ ceramic coating showed favorable toughness and crack resistance. Regarding the erosion resistance of the coatings, the ability of RE-LZ coatings is significantly better than that of LZ coatings, and the erosion rate at 45° and 90° is reduced by 44.9–66.0% and 45.7–62.9%, respectively. • Multi-rare earth doped modified lanthanum zirconate ceramic coating (RE-LZ). • Rare earth modified lanthanum zirconate (LZ) coatings have high plastic deformation capacity. • The modification of multi-rare earths enhanced the fracture toughness of LZ coatings. • The crack resistance of RE-LZ coatings has been greatly improved. • RE-LZ coatings effectively dissipate the energy of erosion particles. [ABSTRACT FROM AUTHOR]