Atomic-scale analyses of Nb 3 Sn on Nb prepared by vapor diffusion for superconducting radiofrequency cavity applications: A correlative study

Jaeyel Lee*, Sam Posen, Zugang Mao, Yulia Trenikhina, Kai He, Daniel L. Hall, Matthias Liepe, David N. Seidman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

We report on atomic-scale analyses of the microstructure of an Nb 3 Sn coating on Nb, prepared by a vapor diffusion process for superconducting radiofrequency (SRF) cavity applications using transmission electron microscopy, electron backscatter diffraction and first-principles calculations. Epitaxial growth of Nb 3 Sn on a Nb substrate is found and four types of orientation relationships (ORs) at the Nb 3 Sn/Nb interface are identified by electron diffraction or high-resolution scanning transmission electron microscopy (HR-STEM) analyses. Thin Nb 3 Sn grains are observed in regions with a low Sn flux and they have a specific OR: Nb 3 Sn //Nb and Nb 3 Sn //Nb The Nb 3 Sn/Nb interface of thin grains has a large lattice mismatch, 12.3%, between Nb and Nb 3 Sn (002) and a high density of misfit dislocations as observed by HR-STEM. Based on our microstructural analyses of the thin grains, we conclude that the thin regions are probably a result of a slow interfacial migration with this particular OR. The Sn-deficient regions are seen to form initially at the Nb 3 Sn/Nb interface and remain in the grains due to the slow diffusion of Sn in bulk Nb 3 Sn. The formation of Sn-deficient regions and the effects of interfacial energies on the formation of Sn-deficient regions at different interfaces are estimated by first-principles calculations. The finding of ORs at the Nb 3 Sn/Nb interface provides important information about the formation of imperfections in Nb 3 Sn coatings, such as large thin-regions and Sn-deficient regions, which are critical to the performance of Nb 3 Sn SRF cavities for accelerators.

Original languageEnglish (US)
Article number024001
JournalSuperconductor Science and Technology
Volume32
Issue number2
DOIs
StatePublished - Feb 2019

ASJC Scopus subject areas

  • Ceramics and Composites
  • Condensed Matter Physics
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry

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