Nucleation and epitaxy growth of high-entropy REBa2Cu3O7– (RE= Y, Dy, Gd, Sm, Eu) thin films by metal organic deposition

High-entropy REBa2Cu3O7–δ (RE = Y0.7 + Dy0.2 + Gd0.2 + Sm0.2 + Eu0.2) (HE-REBCO) superconducting films doped with multiple rare earth elements were successfully fabricated with thickness up to 800 nm by a trifluoroacetate-metal organic deposition (TFA-MOD). The enhanced entropy change ΔS of the HE-REBCO system promotes the c-axis growth of REBCO thin film in the competition with a/b-axis growth. The microstructure and element distribution were investigated by the transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results show that HE-REBCO films have a great amount of stacking defects, lattice distortions and various rare earth oxides. Furthermore, the microstrain of HE-REBCO films increases significantly compared to the undoped YBCO and (Y, Dy)BCO films. Finally, the superconducting critical temperature (Tconset) of HE-REBCO films is about 93 K, and the in-field properties are significantly improved, especially at the temperature of about 77 K. The maximum pinning force density (Fp, max) of the HE-REBCO samples at 77 K is 1.7 times higher than that of the undoped YBCO films.