Results for “Nb6Sn5” | Engineering Papers

DOE OSTI2020

Materials Data on Nb6Sn5 by Materials Project

Nb6Sn5 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are four inequivalent Nb sites. In the first Nb site, Nb is bonded in a 7-coordinate geometry to four equivalent Nb and seven Sn atoms. All Nb–Nb bond lengths are 3.18 Å. There are a spread of Nb–Sn bond distances ranging from 2.96–3.02 Å. In the second Nb site, Nb is bonded in a 12-coordinate geometry to six Nb and six Sn atoms. There are a spread of Nb–Nb bond distances ranging from 2.74–3.20 Å. There are four shorter (2.92 Å) and two longer (3.17 Å) Nb–Sn bond lengths. In the third Nb site, Nb is bonded in a 12-coordinate geometry to six Nb and six Sn atoms. There are two shorter (2.85 Å) and two longer (3.17 Å) Nb–Nb bond lengths. There are a spread of Nb–Sn bond distances ranging from 2.83–3.06 Å. In the fourth Nb site, Nb is bonded in a 6-coordinate geometry to four Nb and six Sn atoms. There are a spread of Nb–Sn bond distances ranging from 2.90–2.97 Å. There are four inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to nine Nb atoms. In the second Sn site, Sn is bonded in a 8-coordinate geometry to eight Nb atoms. In the third Sn site, Sn is bonded in a 8-coordinate geometry to six Nb and two equivalent Sn atoms. There are one shorter (2.78 Å) and one longer (2.91 Å) Sn–Sn bond lengths. In the fourth Sn site, Sn is bonded in a 7-coordinate geometry to seven Nb atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Fabrication of Nb3Sn by Magnetron Sputtering for Superconducting Radiofrequency Application

Particle accelerators are considered as an important device that has wide applications in cancer treatment, sterilizing waste, preserving foods, ion implantation in semiconductor industry, and in production of isotopes for medical applications. Superconducting radiofrequency (SRF) cavities are the building blocks of a linear particle accelerator. Current particle accelerators use niobium (Nb) superconductors as the sheet material to fabricate a single SRF cavity for particle acceleration. With better superconducting properties (critical temperature Tc ~ 18.3 K, superheating field Hsh~ 400 mT), Nb3Sn is considered a potential candidate in SRF technology. Magnetron sputtering is a promising deposition method to fabricate Nb3Sn thin films inside SRF cavities. Superconducting Nb3Sn films were fabricated on Nb and sapphire substrates by magnetron sputtering from a single stoichiometric Nb3Sn target, by multilayer sputtering of Nb and Sn followed by annealing, and by co-sputtering of Nb and Sn followed by annealing. The variation of morphological and superconducting properties was investigated for different substrate temperatures, annealing temperatures, annealing durations, and thicknesses. The film properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDS). The films had crystalline Nb3Sn structure without any presence of poor superconducting Nb6Sn5 and NbSn2 phases. The highest Tc of the films fabricated from the stoichiometric target, multilayer sputtering and co-sputtering were 17.44, 17.93, and 17.66 K respectively. Finally, a cylindrical sputter coater with two identical magnetrons was designed and commissioned to fabricate Nb3Sn films inside a 2.6 GHz SRF cavity. The magnetrons were installed facing opposite to each other in a custom designed vacuum chamber and multilayers of Nb and Sn films on 1 cm2 Nb substrates replicating the beam tubes and equator locations of the cavity and the coated multilayered films were annealed at 950 °C for 3 h. The XRD of the as?deposited and annealed films confirmed the formation of Nb3Sn after the annealing. The dissertation discusses the fabrication process, characterized results of the fabricated films, the design of the cylindrical sputter coater and the preliminary data obtained from the sputter coater.

Sayeed, Md Nizam↗