Decoupling the Formability and Sintering Activity of YBCO Powders for High‐Performance Superconducting Targets

ABSTRACT

Traditionally, ultrafine powders are sought after for their enhanced sintering activity; however, their inadequate formability is frequently neglected. To disentangle these two critical factors, this study conducts a systematic investigation into the sintering behavior of YBCO superconducting targets utilizing powders with markedly different primary particle sizes (640 nm vs. 50 nm) and specific surface areas (1.41 m ² /g vs. 11.84 m ² /g). Despite its higher specific surface area, the finer powder demonstrated substantially inferior compaction performance, resulting in a lower apparent density (1.18 g/cm ³ compared to 1.67 g/cm ³ ) and green compact density (3.16 g/cm ³ at 5 MPa vs. 4.08 g/cm ³ for the coarser powder). Through the design of multi‐path molding and sintering experiments, we effectively isolated the individual contributions of formability and sintering activity. Master sintering curve analysis indicated that the poor formability of the fine powder resulted in a higher apparent densification activation energy (338 ± 5.07–418 ± 6.27 kJ/mol) relative to the coarser powder (313 ± 4.70–382 ± 5.73 kJ/mol), thereby obscuring its inherent sintering advantage. As a result, the target fabricated from the coarser powder, characterized by fewer initial defects and higher green density, exhibited superior final properties, including a density of 5.92 ± 0.22 g/cm ³ , a room‐temperature resistivity of 0.89 ± 0.13 mΩ·cm, and a flexural strength of 60.55 ± 0.91 MPa. This study demonstrates that, for YBCO targets, optimizing green body density through balanced powder characteristics is more crucial than merely pursuing ultra‐fine particle size. The findings offer a robust theoretical foundation for the selection of powder and the design of processes for high‐performance YBCO sputtering targets.