Tensile strain and BaHfO 3 doping modulating proton irradiation effects in REBCO coated conductors

Abstract REBa 2 Cu 3 O 7− δ (REBCO) coated conductors are promising candidates for compact fusion reactors, but their critical current density ( J c ) is vulnerable to degradation under irradiation and mechanical strain. Proton irradiation experiments were conducted on undoped and BaHfO 3 (BHO)-doped REBCO specimens at doses of 1.0 × 10 14 –3.0 × 10 16 protons cm −2 . A general degradation of J c was observed, with the exception of a 5% enhancement in the undoped sample irradiated at 1.0 × 10 14 protons cm −2 and measured at 30 K. Notably, applying tensile strain during irradiation (1.0 × 10 16 protons cm −2 ) significantly accelerated J c degradation, whereas BHO-doped conductors exhibited reduced J c loss due to local compressive strain fields induced by BHO nanoparticles. Density functional theory calculations supported these results, showing that 1% tensile strain lowered the formation energy ( E f ) of O(1) and O(4) vacancies by approximately 0.06 eV and 0.11 eV, respectively, thereby promoting oxygen vacancy formation. Transmission electron microscopy revealed increased defect densities in irradiated and strained conductors, consistent with the more pronounced degradation of J c . These results demonstrated the strong interplay between strain and irradiation effects on REBCO coated conductors and highlight the effectiveness of BHO doping in mitigating J c loss through local strain engineering. This provides practical guidance for designing REBCO conductors for extreme fusion reactor environments.