Critical current enhancement in REBCO coated conductors: Pinning dimensionality, operating windows, and mixed-defect architectures

REBCO (rare-earth barium copper oxide) coated conductors are key materials for high-field technologies, but vortex motion limits their current-carrying performance under practical operating conditions. This review links scalable fabrication, microstructural control, and critical-current enhancement through a dimensional framework for flux pinning. Industrially relevant PLD, MOCVD, and CSD/MOD routes are assessed in terms of manufacturing scale, processing characteristics, and superconducting performance. Artificial pinning centers are classified as localized 0D defects, correlated 1D nanorods or tracks, 2D planar defects and interfaces, and mixed-dimensional architectures. Quantitative comparisons of reported Jc, Ic, pinning force, and operating conditions show that no single defect class is optimal across the full B–T–θ space. Zero-dimensional defects provide broad and relatively weakly anisotropic background pinning, whereas 1D and 2D defects preferentially reinforce directional and planar responses, respectively. Mixed-dimensional landscapes can extend the effective operating window by combining complementary pinning functions, but defect coexistence does not necessarily produce beneficial synergy. Improvements may be offset by Tc suppression, impaired current connectivity, enhanced vortex creep, or reduced structural stability. Reported performance should therefore be interpreted as application-dependent operating windows rather than a universal ranking of pinning strategies. Future progress requires standardized B–T–θ benchmarking, controlled defect transfer to long-length conductors, and reliability evaluation under coupled electromagnetic, mechanical, and thermal loads. These advances will support manufacturable and durable pinning landscapes tailored to the operating envelope of specific superconducting devices.