Processing optimization of mechanochemically activated YBCO powders with La₂O₃ micro-additives for PIT conductor fabrication

This work investigates the role of La₂O₃ introduced as a micro-additive in mechanochemically activated yttrium barium copper oxide (YBa₂Cu₃O₇₋ₓ or YBCO,) powders intended for powder-in-tube (PIT) conductor fabrication. In contrast to conventional rare-earth substitution strategies, La₂O₃ is treated here not as a lattice dopant but is assumed to influence phase formation kinetics during reduced-temperature solid-state synthesis. Mechanical activation was employed to enhance interparticle reactivity and alter diffusion pathways, while controlled micro-additions of La₂O₃ (0–1.5 wt.%) were used to examine their possible influence on phase formation and microstructural development. X-ray diffraction and scanning electron microscopy revealed that small additions (∼0.5 wt.%) are associated with comparatively more favorable Y123 phase development and improved apparent intergranular continuity, whereas higher contents lead to secondary-phase segregation and microstructural degradation. A locally optimal condition within the studied parameter range was identified at 940°C for 10 h, where the balance between reaction completion, grain connectivity, and suppression of excessive secondary-phase formation resulted in the highest transport performance of Ag-sheathed PIT conductors. Superconducting transport is governed primarily by processing-induced microstructural percolation.