TFA-MOD 法における本焼成時の昇温速度が(Y,Gd)Ba₂Cu₃O_y 薄膜の 結晶性及び超伝導特性に及ぼす影響

抄録

REBa₂Cu₃O_y (REBCO)-coated conductors (CCs) derived from the Trifluoroacetates-Metal Organic Deposition (TFA-MOD) process are expected to be used in power applications since they are low-cost and provide high performance. For low-cost production of reel-to-reel system TFA-MOD REBCO CCs, a high rate of productivity during the conversion process is necessary. The heating rate (R_H) during the steps required for conversion is the key factor for realizing a high rate of productivity. In this study, in order to investigate the influence of R_H on microstructures and superconducting properties during the conversion process, we fabricated TFA-MOD (Y,Gd)Ba₂Cu₃O_y ((Y,Gd)BCO) films on SrTiO₃ substrates using different R_H. The (Y,Gd)BCO films with low R_H (< 15C/min) showed a low self-field J_c (J_c^s.f.) due to the formation of a-axis-oriented grains. On the other hand, the films with high R_H (> 25C/min) showed a lower J_c^s.f. because of the formation of non-superconducting phases (Y and Cu-poor). We found that the film fabricated with R_H= 20C/min has high crystallinity, as well as a high J_c^s.f.=4.3 MA/cm² at 77 K compared to those of other films. Optimizing the R_H during the conversion process plays an important role in improving productivity as well as the J_c for TFA-MOD CCs.