Superconducting Joint of GdBa₂Cu₃O_y Coated Conductors by Crystallization of an Additionally Deposited Precursor Layer

Abstract

A superconducting joint of REBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (REBCO) coated conductors (CCs) has been demanded strongly to fabricate long length CCs for high field magnet applications such as nuclear magnetic resonance and magnetic resonance imaging. In the previous reports of superconducting joint, specimens of REBCO CCs were jointed via melting REBCO phases or via solid state diffusion of REBCO phases. In our study, we propose a new method of joint for REBCO CCs. A precursor layer is additionally deposited on GdBCO CC by a metal organic deposition process, and then two pieces of them are stuck together face-to-face and crystallized the precursor to form 123 phase under mechanical pressure in an oxygen atmosphere. The microstructures and temperature dependence of resistance of the jointed sample are characterized by a cross-sectional transmission electron microscopy (TEM) and a four-probe method, respectively. As a result, TEM observation reveals that two CCs are jointed together without formation of secondary phases at the joint interface. Also, temperature dependence of resistance shows Tc onset and Tc zero of 93 K and 82 K, respectively. Consequently, a superconducting joint has been completed successfully. The concept of this method is combining film growth and solid-state diffusion for the additionally deposited precursor layers.