Progress of high-temperature superconducting joints

The increasing resolution of Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) spectrometers requires the use of superconducting magnets to generate higher magnetic field strength. Since the magnetic field limit of Nb3Sn/NbTi low-temperature superconductor (LTS) coils is about 1 GHz (23.5 T), high-temperature superconductors (HTS) with excellent high-field properties have been increasingly used in superconducting coils to increase the magnetic field strength of NMR magnets. The persistent current mode (PM) of superconducting magnets requires uninterrupted current flow in the coils, maintaining strength without external power. Therefore, achieving low resistance in the joints between coils, ideally resulting in a superconducting joint, is crucial. Creating superconducting joints in high-temperature superconductors presents challenges, with significant effort directed toward overcoming them. This paper provides an overview of the preparation technologies for superconducting joints, such as ReBa2Cu3Oy (REBCO, RE = rare earth), BiSrCaCuO (Bi2212, Bi2223), Iron-based Superconductors (IBS), and MgB2. By reviewing the latest advancements to key issues and conducting an in-depth analysis of the technical characteristics of different process schemes in various types of superconducting joints, this article offers valuable references for the preparation of superconducting joints. Graphical abstract