Thermodynamic route of Nb3Sn nucleation: Role of oxygen

Abstract

Intermetallic Nb3Sn alloys have long been believed to form through Sn diffusion into Nb. However, our observations of significant oxygen content in Nb3Sn prompted an investigation of alternative formation mechanisms. Through experiments involving different oxide interfaces (clean HF-treated, native oxidized, and anodized), we demonstrate a thermodynamic route that fundamentally challenges the conventional Sn diffusion mechanism for Nb3Sn nucleation. Our results highlight the critical involvement of a SnOx intermediate phase. This new nucleation mechanism identifies the principles for growth optimization and new synthesis of high-quality Nb3Sn superconductors.

Smooth, homogeneous, high-purity Nb3Sn superconducting RF resonant cavity by seed-free electrochemical synthesis

“…Also, impurities strongly affect the electron mean free path and hence surface resistance. In vapor-diffused Nb 3 Sn, Sn-deficient grains and impurities have been observed at the local surface regions with larger dimensions than the ∼3 nm coherence length [38,42,43]. These crystal defects limit the minimization of BCS resistance and the enhancement of quality factors (table 1).…”