The irradiation response of YBa₂Cu₃O_7-δ coated conductors is closely related to the interaction between artificial pinning centers and irradiation-induced defects. In this work, undoped and BaHfO₃-doped YBCO coated conductors were irradiated with 14 MeV N ions, and their superconducting performance and microstructural evolution were investigated through critical current density measurements, XRD, HRTEM, SAED, and atomistic simulations.

The results show that BHO doping can introduce effective artificial pinning centers, but it also changes the defect landscape and local strain state of the YBCO matrix. After N-ion irradiation, the evolution of critical current density strongly depends on irradiation fluence, temperature, magnetic field, and the presence of BHO nanoparticles. Under severe irradiation conditions, the superconducting performance is significantly degraded. At lower irradiation fluences, however, irradiation-induced defects may contribute to flux pinning enhancement in some samples, while excessive defect accumulation can also weaken superconducting connectivity. Microstructural characterization reveals that N-ion irradiation induces lattice distortion, out-of-plane texture degradation, local disorder, dislocation-like defects, and slight amorphization. Compared with undoped samples, BHO-doped samples show different damage evolution behavior, indicating that BHO nanoparticles and their interface regions may participate in the accommodation and redistribution of irradiation-induced defects. Atomistic simulations further suggest that point defects, especially vacancies, play an important role in the formation of irradiation-induced disorder.

Overall, the irradiation response of YBCO coated conductors is governed by the competition between defect-induced flux pinning enhancement and damage-induced degradation of superconducting transport. These results provide guidance for defect engineering and optimization of YBCO coated conductors for radiation environments.