Abstract: Preformed nanocrystals incorporated into YBa₂Cu₃O_7-δ (YBCO) superconducting thin films prepared by Metal Organic Deposition (MOD) method can effectively enhance the critical current density (J_c) under magnetic fields via flux pinning. The type, initial size, and incorporating concentration of the nanocrystals have significant effects on the flux pinning performance. Therefore, a systematic comparative study on the influence of different nanocrystal incorporation conditions on the growth quality and superconducting properties of YBCO films is required. In this study, BaHfO₃ (BHO) and BaZrO₃ (BZO) nanocrystals with initial sizes of 6 nm and 12 nm were prepared and incorporated into YBCO films with a thickness of 2.4 μm at molar concentrations of 5% and 10%. The growth quality and superconducting properties of the films after nanocrystal incorporation were systematically characterized. The experimental results showed that under 77 K self-field conditions, the critical current (I_c) of the films with 5% nanocrystal incorporation exceeded 600 A (12 mm width). When the applied magnetic field exceeds 1 T, the film with 10% 6 nm BHO nanocrystals exhibited the best in-field property across the temperature range of 4.2, 50, and 77 K, with the J_c reaching 14.28 MA/cm² (4.2 K, 3 T). Comparative analysis indicates that, in enhancing the in-field property of YBCO thin films, the incorporation of nanocrystals at 10% concentration is more effective than that at 5% for the same type of nanocrystals, and the initial size has a more pronounced effect on the flux pinning performance of BHO nanocrystals than that of BZO nanocrystals. This study provides experimental evidence for optimizing nanocrystal incorporation strategies to improve the in-field property of MOD-YBCO films.

Key words: YBa₂Cu₃O_7-δ, flux pinning, BaHfO₃, BaZrO₃