Effect of the density of states at the Fermi level on defect free energies and superconductivity: A case study of 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Nb</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mi>Sn</mml:mi></mml:mrow></mml:math>

Sitaraman, Nathan; Kelley, Michelle M.; Porter, Richard F.; Liepe, Matthias; Arias, T. A.; Carlson, Joe; Pack, Alden; Transtrum, Mark K.; Sundararaman, Ravishankar

doi:10.1103/physrevb.103.115106

Cited by 12 publications

(11 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Off stoichiometry of the Nb 3 Sn structure is known to be dominated by antisite disorder [36], with the density of vacancies remaining negligible [37]. Work on SRF cavity materials using density functional theory to model antisite disorder in Nb 3 Sn has shown Nb Sn antisite defects cluster together to form tin-depleted regions at free surfaces [38]. The grain size in RRP ® materials is so small that it is possible that the combination of the depletion of Nb at the grain boundaries shown in figure 7 and the resulting clustering of Nb Sn defects in the surrounding grains produce the observed regions of increased Nb concentration, and that they are kinetically stabilised by the very slow diffusion rate of Nb towards the grain boundaries even at the final reaction temperature.…”

Section: Discussionmentioning

confidence: 99%

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Wheatley

Baumgartner

Eisterer

et al. 2023

Supercond. Sci. Technol.

View full text Add to dashboard Cite

Atom Probe Tomography has been used to study the effect of fast neutron irradiation on the local chemistry of Nb3Sn samples. Two RRP® wires doped with 2 at% Ti were analysed, one in the as-received condition and the other irradiated to a neutron fluence (E>0.1MeV) of 2.82x1022 m-2 in the TRIGA-II reactor. The irradiated sample had a reduced Tc, an increase in Fp, a shift in the peak of the Fp curve suggesting the introduction of secondary point pinning, and an increase in the estimated scaling field B*. Atom Probe Tomography analysis has shown that polycrystalline Nb3Sn has three distinct regions of composition, near stoichiometry Nb3Sn (low Nb), regions with a higher Nb content than expected in equilibrium Nb3Sn (high Nb) and grain boundaries. The summed composition of these three regions lies within the Nb3Sn phase for both the as-received and irradiated samples. The distinct regions of high Nb Nb3Sn demonstrate incomplete diffusion in the as-received sample, and the reduction in volume of these high Nb regions after irradiation implies significant radiation induced diffusion has occurred. The occurrence presence of other features in the atomic-scale chemistry, such as the extent of Cu segregation at grain boundaries, and to three types of dislocation array, and unreacted Nb nanoparticles, are compared between samples.

show abstract

Section: Discussionmentioning

confidence: 99%

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Wheatley

Baumgartner

Eisterer

et al. 2023

Supercond. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…The adoption of thinner films suggests a roughness reduction; nevertheless, the reproducibility of their RF performance has been an issue, probably due to their excessive thinness (versus the field penetration depth) and subsequent interface issues [27]. Furthermore, stoichiometric variations dramatically degrade T c and induce local heating; for example, a 3 at.% variation reduces T c by 50% (figure 1(c)) [30][31][32][33]41]. Also, impurities strongly affect the electron mean free path and hence surface resistance.…”

Section: Introductionmentioning

confidence: 99%

“…Studies on vapor-diffused Nb 3 Sn [32,38,42] suggest that these material issues arise from insufficient and non-uniform Sn-vapor supply. Local variations in Sn flux during vapor diffusion result in an uneven spatial distribution of growth rates, attributing to roughness.…”

Section: Introductionmentioning

confidence: 99%

“…Local variations in Sn flux during vapor diffusion result in an uneven spatial distribution of growth rates, attributing to roughness. Likewise, inadequate Sn sources and slow supply rates produce initially Sn-deficient grains [30,31] and calculated [32,33] data). ('bad' Nb 3 Sn) following the 18 at.%-Sn boundary in the phase diagram; subsequently, slow Sn diffusion within these grains kinetically limits their conversion into stoichiometric 'good' Nb 3 Sn [32,38,44,45].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Sun,

Baraissov,

Porter

et al. 2023

Supercond. Sci. Technol.

View full text Add to dashboard Cite

Workbench-size particle accelerators, enabled by Nb3Sn-based superconducting radio-frequency (SRF) cavities, hold the potential of driving scientific discovery by offering a widely accessible and affordable source of high-energy electrons and X-rays. Thin-film Nb3Sn RF superconductors with high quality factors, high operation temperatures, and high-field potentials are critical for these devices. However, surface roughness, non-stoichiometry, and impurities in Nb3Sn deposited by conventional Sn-vapor diffusion prevent them from reaching their theoretical capabilities. Here we demonstrate a seed-free electrochemical synthesis that pushes the limit of chemical and physical properties in Nb3Sn. Utilization of electrochemical Sn pre-deposits reduces the roughness of converted Nb3Sn by five times compared to typical vapor-diffused Nb3Sn. Quantitative mappings using chemical and atomic probes confirm improved stoichiometry and minimized impurity concentrations in electrochemically synthesized Nb3Sn. We have successfully applied this Nb3Sn to the large-scale 1.3 GHz SRF cavity and demonstrated ultra-low BCS surface resistances at multiple operation temperatures, notably lower than vapor-diffused cavities. Our smooth, homogeneous, high-purity Nb3Sn provides the route toward high efficiency and high fields for SRF applications under helium-free cryogenic operations.

show abstract

“…Additionally, niobium and Sn react differently to the chemicals used, which can lead to different removal rates for each element, thus changing the surface stoichiometry. Even a small change in the stoichiometry away from Nb3Sn can cause a decrease in Tc [7].…”

Section: Introductionmentioning

confidence: 99%

Improving Nb3Sn Cavity Performance Using Centrifugal Barrel Polishing

Viklund

Burk

Seidman³

et al. 2023

Improving Nb3Sn Cavity Performance Using Centrifugal Barrel Polishing

View full text Add to dashboard Cite

In this study we will show a new method of polishing for Nb3Sn cavities known as centrifugal barrel polishing (CBP). Using this method, Nb3Sn coated samples are polished to a surface roughness comparable to a traditional Nb cavity after electropolishing (EP). We also investigate different methods of cleaning the Nb3Sn surface after CBP to remove residual abrasive particles. The polished Nb3Sn surface is analyzed using confocal laser microscopy, and scanning electron microscopy (SEM) is used to image the surface and measure the surface roughness after polishing. Transmission electron microscopy (TEM) is also used for high resolution analysis of the surface after polishing. Finally, we show that centrifugal barrel polishing can improve the performance of a Nb3Sn SRF cavity.

show abstract

Effect of the density of states at the Fermi level on defect free energies and superconductivity: A case study of Nb3Sn

Cited by 12 publications

References 64 publications

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

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

Improving Nb3Sn Cavity Performance Using Centrifugal Barrel Polishing

Contact Info

Product

Resources

About

Effect of the density of states at the Fermi level on defect free energies and superconductivity: A case study of Nb3Sn

Cited by 12 publications

References 64 publications

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb3Sn RRP® wires using atom probe tomography

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb3Sn RRP® wires using atom probe tomography

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

Improving Nb3Sn Cavity Performance Using Centrifugal Barrel Polishing

Contact Info

Product

Resources

About

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

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