Biopolymer mediated synthesis of plate-like YBCO with enhanced grain connectivity and intragranular critical current

Abstract

We present a biochemical synthesis protocol for the efficient production of strongly anisotropic, plate-like crystallites of YBa₂Cu₃O_7–δ (YBCO) of typical dimension 6 μm × 6 μm × 1 μm. The hierarchical structure of these crystallites, revealed by transmission electron microscopy, is responsible for an unprecedented bulk intragranular critical current density reaching 0.1 MAcm⁻² at 77 K—an order of magnitude higher than commercially sourced powder material. Further, we show that a naturally-occurring close alignment of adjacent plate-like grains leads to an electrical connectivity that allows an intergranular supercurrent to flow. This work provides an important starting point for an alternative route to the synthesis of YBCO conductors that has the potential to overcome many of the limitations of existing thin film based approaches.