There are low-temperature superconductors (LTS) and high-temperature superconductors (HTS). HTS transition temperatures are still well below 0° Fahrenheit or Celsius, but researchers all over the world endeavor to create materials with higher transition temperatures because a room-temperature superconductor would be a Holy Grail of clean energy. Ambature’s roots are in HTS research, and many of our designs incorporate a-axis yttrium barium copper oxide (YBCO) and other members of the REBCO or cuprate family of superconductors. “Rare Earth” in REBCO is a misnomer—many of the elements are abundant in nature and widely used. You can find them in the electric motors of hybrid and electric vehicles, for example. Mining rare earth elements, much like mining any other resource, has limited environmental impact if safety standards and environmental regulations are followed, and rare earth recycling is increasing.

YBCO transitions at around 90 Kelvin (-298°F or -183°C), which means it can be cooled by liquid nitrogen. Liquid nitrogen is abundant, cost-effective, and used extensively in food processing and other industries, so there is a wealth of expertise in place to deal with liquid nitrogen at industrial scales. Real-world factors determine cooling performance, but we can use ideal calculations to explore potential gains. Cooling HTS to 77K with liquid nitrogen requires, ceteris paribus, about four percent of the power required to cool LTS to 4K with liquid helium. Increased noise at higher temperatures will not be suitable for all applications, but an optimal balance can be struck. Helium is also limited and more expensive than nitrogen. In our own lab activities, liquid helium costs more than 17 times as much as liquid nitrogen, including helium regeneration.

Ambature once produced an a-axis YBCO/NBCO superlattice that partially transitioned above 200K, prompting our national lab partners at the time, a division of NASA’s Jet Propulsion Laboratory, to publish that Ambature has “fabricated and tested a material that arguably holds promises for room temperature superconductivity.” A superlattice is a compound superconductor comprising many layers of superconducting materials. Each layer reinforces the stack to achieve a higher transition temperature. We are growing and testing new superlattices this quarter to further investigate the potential of a-axis HTS.