Preparation and Superconducting Properties of Nb3Sn Films by Electroplating and Electroless plating Methods

For this study, Nb3Sn superconducting films were prepared on Nb substrates using Sn electroplating and electroless Sn plating, followed by high-temperature annealing. After Sn layers were deposited on electropolished Nb substrates, subsequent annealing at 950 ℃ or 1100 ℃ enabled Nb3Sn formation through solid-state diffusion. Structural analyses using X-ray diffraction and X-ray photoelectron spectroscopy confirmed Nb3Sn phase formation by both plating methods, with electrodeposition yielding more uniform Sn layers and more reproducible Nb3Sn formation. Sn deposition exhibited poorer uniformity, but appropriate annealing conditions still enabled Nb3Sn formation. Repeated annealing cycles promoted deeper Sn diffusion into the Nb substrate, resulting in Nb3Sn layer formation beneath the surface, which might mitigate the mechanical fragility inherent in Nb3Sn. Superconducting measurements revealed transition temperatures of 17.9-18.0 K for electroplated samples and 17.5 K for electroless plating samples, including those with subsurface Nb3Sn layers. These results demonstrate wet-chemical plating combined with thermal treatment as a promising and versatile approach to achieve Nb3Sn coating formation for superconducting radio-frequency cavities.