High critical currents in heavily doped (Gd,Y)Ba2Cu3Ox superconductor tapes

Abstract

REBa2Cu3Ox ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (Jc) above 20 MA/cm2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba2Cu3Ox superconductor tapes, which is more than three times higher than the Jc typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m3 have also been attained at 20 K. A composition map of lift factor in Jc (ratio of Jc at 30 K, 3 T to the Jc at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO3 (BZO) nanocolumn defect density of nearly 7 × 1011 cm−2 as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high Jc films.

Over 15 MA/cm2 of critical current density in 4.8 µm thick, Zr-doped (Gd,Y)Ba2Cu3Ox superconductor at 30 K, 3T

“…This J c value also compares very well with the record high J c value of 20.1 MA cm −2 reported at 30 K, 3T in 0.9 µm thick, 25 mol% Zr added GdYBCO film made by conventional MOCVD 13,15 . The J c results are summarized in Table 1.…”

“…One particular aspect of interest was maximizing the lift factor (LF), defined as the ratio of I c at desired temperature/field and I c value at 77 K, self-field itself 12–15 . Extensive optimization of the REBCO-BZO system has been done using MOCVD, in terms of dopant concentration, film microstructure, growth conditions and composition to achieve high in-field performance 13,16–18 . However, common to most REBCO film growth techniques, J c was typically found to strongly deteriorate with thickness 19–21 .…”

“…If this goal is achieved, it will greatly simplify the deposition process of thick films due to single pass deposition compared to conventional MOCVD. In addition, if the same high performance is maintained throughout the thickness as in lower thickness tapes 13,15,23 , it will enhance the engineering current density ( J e ) significantly, which will in turn decrease the cost/performance ratio.…”

Upward shift of the vortex solid phase in high-temperature-superconducting wires through high density nanoparticle addition

“…5c, overall the +3BZO wire shows an extremely high μ 0 H irr at 65 K, at 30 T ( H ||45°) and 24 T ( H || c ) and at 50 K, 58 T ( H ||45°) and 45 T ( H || c ), values which to our knowledge are the highest reported for practical HTS wires31 as well as for thin films on single-crystal substrates32. Recently, very high μ 0 H irr  = 14.8 and 15.8 T at 77 K ( H || c ) were observed in a heavily BZO nanorod-doped (Y,Gd)BCO wire grown by metal organic chemical vapor deposition3334 and BaHfO 3 doped PLD GdBCO wire35; these methods could also translate to great improvements of H irr at high fields. This indicates that a high density of NPs/columns is beneficial not only for MOD prepared materials but is a general trend for REBCO wires.…”

Tuning nanoparticle size for enhanced functionality in perovskite thin films deposited by metal organic deposition

“…34,45 At high temperatures, the +12BHO (d coat = 30 nm) film shows a maximum F p = 33 GN m − 3 at 77 K and 124 GN m − 3 at 65 K. Moreover, at T = 26 K, the F p of the +12BHO (d coat = 30 nm) film reaches a nearly constant~677 GN m − 3 from μ 0 H43 T up to 9 T, an F p value 10 times greater than that of Nb 3 Sn at 4.2 K. 46 Because the pinning landscape is produced by NPs, F p measured along the c-axis is actually close to the minimum value as a function of angle, not the maximum, contrary to the case of films with NRs, 45 as can be observed in the J c (θ) curves of Figures 4d-f. For the +12BZO (d coat = 150 nm) film, the BZO NPs are much less effective at 26 K than at a higher T. However, for the +12BHO (d coat = 30 nm) film, we see significant J c increases for all orientations and temperatures compared with that of the BZO MOD films, with a higher J c minimum (J c,min ) than that previously reported for any REBCO film or wire. 17,21,45,47,48 Relation between flux creep and NP density The different temperature dependence of the J c improvement (seen in the J c ratio) between BZO and BHO has its origin in the NP size (D NP ) relative to the normal-core diameter (2ξ ab ), as shown in Figure 5a. For BZO (D NP~2 5 nm), D NP /2ξ ab is 1.5 at 80 K but 44 at low temperatures, whereas for BHO (D NP~7 nm), d/2ξ ab ⩽ 1 and~2 at high and low temperatures, respectively.…”