Preparing Superconducting YBCO Colloids via a Top-Down Processing Route for Applications in Soft Composites

High-temperature superconductors (HTSCs) are critical materials for magnetic, power, and energy storage applications. The cuprate-based HTSCs, such as yttrium barium copper oxide, YBa₂Cu₃O_7-δ (YBCO), allow for superconducting devices at a critical temperature (T _c) above 90 K, which is easily accomplished via cryogenic liquid nitrogen. One challenge of HTSCs is the need for high crystallinity of an oxygen-deficient perovskite solid, which can only be achieved via high-temperature solid-state synthesis and subsequent annealing. HTSCs have ceramic-like physical properties and are not easily processed or chemically synthesized to colloidal sizes at scale. Herein, we developed a multistep top-down processing method to break YBCO into finer ligand-stabilized colloids, which could then be suspended in solvents as a concentrated paste or ink. We show the potential of such inks by dispersing YBCO in poly-(dimethylsiloxane) (PDMS) elastomer molds, creating superconducting soft composites. Using this approach, we found that chemical stoichiometry and crystal structure of the parent YBCO are preserved, and thus the final colloids are also superconductive. Powder X-ray diffraction and scanning electron microscopy confirmed the preservation of crystal structure and grain morphology, while Meissner effects and quantum locking observations, coupled with magnetic susceptibility measurements, revealed trends in superconductivity and T _c. Finally, we show how the soft YBCO-PDMS elastomers have superconductive properties that are a function of the YBCO weight percent, which can be easily tailored.