Atomic-scale analyses of Nb3Sn on Nb prepared by vapor diffusion for superconducting radiofrequency cavity applications: a correlative study
| Autor: | Zugang Mao, Y. Trenikhina, Daniel Hall, Sam Posen, David N. Seidman, Jaeyel Lee, Matthias Liepe, Kai He |
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| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Materials science Condensed matter physics Metals and Alloys Substrate (electronics) Condensed Matter Physics Epitaxy Microstructure 01 natural sciences Atomic units Electron diffraction Transmission electron microscopy 0103 physical sciences Scanning transmission electron microscopy Materials Chemistry Ceramics and Composites Electrical and Electronic Engineering 010306 general physics Electron backscatter diffraction |
| Zdroj: | Superconductor Science and Technology. 32:024001 |
| ISSN: | 1361-6668 0953-2048 |
| DOI: | 10.1088/1361-6668/aaf268 |
| Popis: | We report on atomic-scale analyses of the microstructure of an Nb3Sn 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 Nb3Sn on a Nb substrate is found and four types of orientation relationships (ORs) at the Nb3Sn/Nb interface are identified by electron diffraction or high-resolution scanning transmission electron microscopy (HR-STEM) analyses. Thin Nb3Sn grains are observed in regions with a low Sn flux and they have a specific OR: Nb3Sn //Nb and Nb3Sn //Nb The Nb3Sn/Nb interface of thin grains has a large lattice mismatch, 12.3%, between Nb and Nb3Sn (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 Nb3Sn/Nb interface and remain in the grains due to the slow diffusion of Sn in bulk Nb3Sn. 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 Nb3Sn/Nb interface provides important information about the formation of imperfections in Nb3Sn coatings, such as large thin-regions and Sn-deficient regions, which are critical to the performance of Nb3Sn SRF cavities for accelerators. |
| Databáze: | OpenAIRE |
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