Speaker
Description
REBCO-based high-temperature superconducting (HTS) tapes are strong candidates for next-generation AC power applications due to their high current density and compact geometry. However, AC losses remain a major obstacle to their widespread deployment. Patterned Superconductors for AC Loss Minimisation (PSALM) tapes offer a promising solution by embedding Roebel-inspired patterns directly within the superconducting layer, enabling significant loss reduction. Extending this concept to multilayer architectures with oppositely oriented meander patterns can further suppress AC losses through magnetic field cancellation.
A critical challenge in fabricating multilayer PSALM tapes is maintaining the superconducting performance of underlying REBCO layers during high-temperature deposition processes such as pulsed laser deposition (PLD). Oxygen out-diffusion at elevated temperatures leads to degradation of superconducting properties. Compared to epitaxial thin films, REBCO tapes possess smaller grains, higher grain boundary density, and increased porosity, which enhance oxygen diffusion.
In this work, we aim to improve oxygen retention and thermal stability of REBCO tapes by modifying their microstructure. A controlled high-temperature pre-annealing treatment (650–800 °C) in an inert atmosphere is employed to promote grain growth and reduce grain boundary density, followed by re-oxygenation annealing to restore oxygen stoichiometry. The annealing parameters are optimized to avoid structural damage or decomposition of the tape.
The treated tapes are subsequently subjected to controlled deoxygenation for 90 s at temperatures ranging from 650 to 850 °C, mimicking the thermal conditions experienced in the deposition zone during multilayer growth. The samples are then characterized using structural, transport, and magnetic measurements to assess grain evolution, oxygen homogeneity, and superconducting performance. This approach provides a viable pathway toward thermally robust multilayer REBCO architectures suitable for PSALM tape fabrication and advanced AC loss reduction.