Effect of Hf addition on critical current density of (Y,Eu)Ba₂Cu_3.6O_7-δ thin films prepared by trifluoroacetate metal organic deposition

Highlights: • This work firstly introduce the Eu and Hf co-doping effect on the performance of YBa₂Cu_3.6O_7-δ thin films, prepared on oxide buffered metallic substrates by trifluoroacetate metal organic deposition (TFA-MOD). • (Y, Eu)Ba₂Cu_3.6O_7-δ film showed a very different surface morphology, smooth and regular, compared to YBa₂Cu_3.6O_7-δ thin film, which has never been reported before. • The J_c value under self-field of (Y, Eu)Ba₂Cu_3.6O_7-δ thin film was obviously improved compared to YBa₂Cu_3.6O_7-δ thin film. • (Y, Eu)Ba₂Cu_3.6O_7-δ thin film with Hf addition exhibited enhancement of J_c value under magnetic fields. - Abstract: The critical current density (J_c) performance of YBCO coated conductors (CCs) under magnetic field has become a considerable limitation for its commercial application in recent years. It is well known that the proper amount of element doping into the CCs is a convenient method to increase flux pinning and then to enhance the J_c. In the present work, we firstly introduce the co-doping of Eu and Hf and study the effect on the performance of YBa₂Cu_3.6O_7-δ thin films. Three types of high temperature superconducting thin films, i.e., YBa₂Cu_3.6O_7-δ, (Y,Eu)Ba₂Cu_3.6O_7-δ and Hf doped (Y,Eu)Ba₂Cu_3.6O_7-δ were prepared on the oxide buffered metallic substrates by using trifluoroacetate metal organic deposition (TFA-MOD). The component and structure of the as-prepared samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and atomic force microscopy (AFM). Superconducting properties were measured with a SQUID magnetometer. It was revealed that the (Y,Eu)Ba₂Cu_3.6O_7-δ thin films exhibit better out-plane and in-plane texture compared with the pure YBa₂Cu_3.6O_7-δ thin film. The J_c of (Y,Eu)Ba₂Cu_3.6O_7-δ thin film was improved compared with pure YBCO thin film. In case of Hf doping, however, the biaxial texture became worse while the in-field J_c performance was enhanced, implying the increase of flux pinning with proper Hf addition.