Superconducting Joint for REBCO-Coated Conductors without Oxidization Annealing via Low-temperature Synthesis Reaction Using Potassium Hydroxide

Abstract

Synopsis : Recently, several novel techniques for creating superconducting joints between two REBCO-CCs have been suggested. These techniques include long-time oxidization annealing to compensate the oxygen deficiency of REBCO due to the high processing temperature. In this paper, a superconducting joint was achieved via a one-time heat treatment at the low temperature of 525ºC without oxidization annealing. The jointed GdBCO-CCs were prepared in three steps. The first step is that Eu–Ba–Cu–O raw material was placed between Ag-removed Gd123 layers of the CC. In the second step, the sample was mechanical pressurized using two plates of metal. Finally, the sample was heat-treated at 525ºC in KOH vapor. All steps were performed at ambient pressure. The jointed sample was bonded finely and showed T conset = 76.7 K and T czero = 57.5 K inclusive of the jointed region. From XRD observation of the jointed region in the samples, both GdBCO-CC and EuBCO-pressed materials contained incomplete RE123, RE247 and RE124 phases.