Phase Evolution of Superconducting Sn-In-Bi Solder Alloys


Mousavi T., AKSOY C., Grovenor C., Speller S.

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, vol.26, no.3, 2016 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 26 Issue: 3
  • Publication Date: 2016
  • Doi Number: 10.1109/tasc.2016.2514843
  • Journal Name: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Keywords: Microstructure, phase evolution, solders, superconducting properties, HIGH-FIELD NMR, SYSTEM, JOINT

Abstract

Development of Pb-free superconducting solders is of great importance for the superconducting magnet manufacturers who often use Pb-Bi alloys as superconducting solders. Here, we study the phase evolution, microstructure, and superconducting properties of a number of alloys in the Pb-free Sn-In-Bi system using analytical scanning electron microscopy, differential thermal analysis, X-ray diffraction, and SQUID magnetometry. All the alloys exhibit melting points below 200 degrees C and superconducting transition temperatures above 4.2 K. The choice of initial composition and cooling rate controls the microstructure ( chemistry, volume fraction, morphology, and scale) of these alloys and strongly influences the final superconducting properties. The In-rich beta-phase shows better superconducting properties compared with the other phases in the Sn-In-Bi system. As a result, by increasing the indium content in the alloy, volume fraction of the In-rich beta-phase increases, leading to lower melting point, higher wettability, and better superconducting properties.