Cheaper Conductive High-Temperature Superconductors will Soon Come from 3D Printers

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At the Chair of Digital Additive Production (DAP) at RWTH Aachen University, a process chain is being developed that allows high-temperature superconductors to be printed ...

Currently, the most technologically established materials are so-called low-temperature superconductors, say the experts from DAP. However, high-temperature superconductor material, such as yttrium-barium-copper oxide (YBCO), can enable more favorable operating conditions because such superconductors can be relatively easily cooled with liquid nitrogen, as has been explained. Their use, however, has so far been limited to a few, highly predefined component shapes. This is expected to change in the future. Additive manufacturing processes could fundamentally open up new degrees of freedom in component design, according to statements from Aachen. At the same time, the complex material-physical properties of YBCO place high demands on the entire process chain. This is because YBCO is a brittle—quite fragile – oxide ceramic with a complex, oxygen-dependent crystal structure. If the chemical conditions in the material and the oxygen arrangement in the crystal lattice change, it negatively impacts the superconducting properties, it is further explained.

This is being done at the DAP Chair in Terms of Superconductor Printing:

Thus, the issue arises that the typically strong temperature gradients and atmospheric conditions in additive manufacturing directly impact the microstructure and porosity of the YBCO material. Against this backdrop, researchers are now systematically examining the interplay between material, process control, and geometry. The chosen additive manufacturing method is powder bed-based laser beam melting (PBF-LB). To this end, a process-compatible powder preparation and an adapted manufacturing strategy are being developed. Both aim to preserve the phase structure relevant for superconductivity (referred to as Y-123) throughout the process chain. As part of the development of suitable YBCO powder (from yttrium oxide, copper oxide, and barium carbonate), experts specifically adjusted particle size, flowability, and chemical composition, it is further explained. This is intended to enable uniform powder layers with reproducible quality in PBF-LB. Building on this, key process parameters have already been tailored to ensure sufficient particle bonding while also limiting thermal stress on the phase structure critical to superconductivity.

The First Additively Manufactured Test Specimens Made of YBCO Already Exist

Initial test specimens have already been successfully produced in reproducible geometry using a two-pass exposure with a defocused laser beam (Image 1). Functionally, however, they initially showed no detectable superconducting properties. Phase analyses revealed structural changes and a reduced proportion of the superconducting Y-123 phase. However, the superconducting properties could be restored through targeted heat treatment under oxygen exposure. The samples then exhibited the characteristic resistance drop at low temperatures as well as pronounced diamagnetic effects in the so-called Meissner test (Image 2). This proves that the structural changes induced during the additive process are not irreversible but can be corrected. The systematic comparison of the powder, the laser-fabricated state, and the heat-treated structure allows for a clear assignment of phase development and its effects on the superconducting properties along the additive process chain. This makes it understandable under which conditions superconducting properties can be maintained or restored. Unfortunately, it became apparent that the mechanical stability of the additively manufactured structures is a limiting factor for application—a central bottleneck for advancing to load-bearing component applications, as the researchers admit.