Researchers at the University at Buffalo have made significant strides toward this goal. A study published in Nature Communications on Aug. 7 details the fabrication of the highest-performing HTS wire segment to date, significantly improving its cost-performance metric.
Using rare-earth barium copper oxide (REBCO), the team achieved unprecedented critical current density and pinning force - the amount of electrical current carried and the ability to pin magnetic vortices, respectively - across all magnetic fields and temperatures from 5 to 77 kelvin.
"These results will help guide industry toward further optimizing their deposition and fabrication conditions to significantly improve the price-performance metric in commercial coated conductors," says Amit Goyal, PhD, SUNY Distinguished Professor and SUNY Empire Innovation Professor in the Department of Chemical and Biological Engineering at UB. "Making the price-performance metric more favorable is needed to fully realize the numerous large-scale, envisioned applications of superconductors."
Diverse Applications of HTS Wires
HTS wires are promising for various applications, including doubling power generation from offshore wind generators, creating grid-scale superconducting magnetic energy storage systems, and enabling loss-less power transmission in high current DC and AC lines. They also hold potential for highly efficient superconducting transformers, motors, and fault-current limiters for the grid.
One particularly exciting application is commercial nuclear fusion, which could generate limitless clean energy. In recent years, around 20 private companies have been founded globally to develop commercial nuclear fusion, with substantial investments in HTS wire development.
Additional applications include next-generation MRI for medicine, advanced nuclear magnetic resonance (NMR) for drug discovery, and high-field magnets for physics research. Defense applications also abound, such as in the development of all-electric ships and airplanes.
Record-Breaking Performance
In their latest work, Goyal's team reports ultra-high performance in REBCO-based superconducting wires. At 4.2 kelvin, these wires carried 190 million amps per square centimeter without any external magnetic field and 90 million amps per square centimeter under a 7-tesla magnetic field. At 20 kelvin, they maintained over 150 million amps per square centimeter without a magnetic field and over 60 million amps per square centimeter at 7 tesla.
This corresponds to a 4-millimeter-wide wire segment carrying a supercurrent of 1,500 amps at self-field and 700 amps at 7 tesla at 4.2 kelvin. At 20 kelvin, the values were 1,200 amps at self-field and 500 amps at 7 tesla.
Notably, the HTS film, despite being only 0.2 microns thick, could carry a current comparable to that of commercial superconducting wires with HTS film almost 10 times thicker. The wires also exhibited strong magnetic vortex pinning, with forces of about 6.4 teranewtons per cubic meter at 4.2 kelvin and 4.2 teranewtons per cubic meter at 20 kelvin under a 7-tesla magnetic field.
"These results demonstrate that significant performance enhancements are still possible and hence the associated reduction in cost that could potentially be realized in optimized, commercial HTS wires," Goyal says.
Fabrication Process
The HTS wire segment was created using ion-beam assisted deposition (IBAD) MgO technology and nanocolumnar defects via simultaneous phase-separation and strain-driven self-assembly technology. This method allows for the incorporation of insulating or non-superconducting nanocolumns at nanoscale spacings within the superconductor, effectively pinning the superconducting vortices and enabling higher supercurrents.
"The high critical current density was made possible by a combination of pinning effects from rare-earth doping, oxygen-point defects, and insulating barium zirconate nanocolumns and their morphologies," Goyal says.
"The HTS film was made using an advanced pulsed laser deposition system via careful control of deposition parameters," adds Rohit Kumar, postdoctoral fellow in the UB Laboratory for Heteroepitaxial Growth of Functional Materials and Devices, which Goyal leads.
Goyal noted that they conducted atomic-resolution microscopy using advanced microscopes at the Canadian Center for Electron Microscopy at McMaster University for characterizing nanocolumnar and atomic-scale defects and also performed some superconducting property measurements at the Universita di Salerno in Italy.
Research Report:Ultra-high Critical Current Density and Pinning Force in Nanostructured, Superconducting REBCO-based, Coated Conductor
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