In-field critical current and pinning mechanisms at 4.2 K of Zr-added REBCO coated conductors

Abstract

The critical current and pinning mechanisms at 4.2 K have been studied over a magnetic field range of 0-14 T for Zr-added (0, 5 and 15 mol.%) REBa 2 Cu 3 O 7-x (REBCO and RE = rare earth) coated conductors fabricated by advanced metal organic chemical vapor deposition (A-MOCVD). It is found that the (Ba + Zr)/Cu content in Zr-added (5 and 15 mol.%) REBCO affects the critical current at 77 K, 0 T as well as density, continuity and shape of BaZrO 3 (BZO) self-assembled nanocolumns and RE 2 O 3 in-plane precipitates that significantly enhance the pinning force density Fp(H) as well as isotropic pinning landscape at 4.2 K. In addition to bell-shape dependence of critical current density, J c , at 4.2 K with (Ba + Zr)/Cu content we observed an unusual Fp(H) behavior correlated to particular type of pinning centers, morphology and distribution that have been revealed by TEM microstructure analysis. By fitting the Dew-Hughes equation of the pinning force density Fp(H) at 4.2 K we extract the scaling behaviors of the Fp(H) associated with the competition of pinning mechanisms driven by vertically-aligned BZO nanorods and in-plane RE 2 O 3 pinning defects. This result sheds light on approaches towards interactive control of strong and isotropic pinning centers in Zr-added REBa 2 Cu 3 O 7-x (REBCO and RE = rare earth) coated conductors, and especially understanding the correlation between microstructural characteristics and vortex pinning mechanisms at 4.2 K in high magnetic fields.

Self-Organized Nanocomposite Structure Controlled by Elemental Site Occupancy to Improve Vortex Pinning in YBa2Cu3O7 Superconducting Films

“…Figure compares the F p – B curves of the YBCO+BLuNO and the YBCO+BYbNO films at almost the same nominal volume fraction of the nanorod. The F p peak at 77 and 65 K is observed in the magnetic field of 1.5–2.5 T in the YBCO+BLuNO and YBCO+BYbNO films, and the peak is not clear in YBCO+BLuNO(5) at 40 K. The vortex behavior changes at the matching field, − and the peak field corresponds to the matching field. ,, The F p peak was also observed at the higher magnetic field in the YBCO+BYbNO film in the cases of 2.7–3 vol % and 9–10 vol % (Figure a,c). While the F p near 2 T is the same level in the YBCO+BLuNO(5) and the YBCO+BYbNO(4.5) films, the F p is larger in the YBCO+BLuNO film both for B < ∼1 T and for B > ∼3 T. This behavior is observed regardless of the nanorod content.…”

Development and large volume production of extremely high current density YBa2Cu3O7 superconducting wires for fusion

“…A common approach to enhance J c in magnetic field has been to introduce artificial pinning centres (APC) of c-axis correlated nano-columns of various perovskites [21][22][23][24][25] , a technique utilised in commercial PLD 28,29,38 and metalorganic chemical vapour deposition (MOCVD) film growth 6 . Although the highest J c (B) values have been obtained in this way [39][40][41] , the complex HTS film nanostructure results in considerable spread in commercial wire in-field performance 26,27 and greatly narrows the processing window, requiring slower deposition rates to achieve maximum J c enhancement 28,29 . For 2G HTS wire with nano-columnar APC, more typical is a faster decay of critical current with increasing magnetic field than for wire without APC 42 .…”

“…To further increase J E , we deposited thick YBCO films on a thin (40 μm thick) substrate. Although both these approaches are straightforward and are generally followed for the purpose 6,21,[39][40][41]50,51 , they are nontrivial to implement in economical, high yield production. For thick REBCO films typical is the decay of microstructure and J c when the film thickness exceeds 1 micron.…”

Low-Fluorine Ba-Deficient Solutions for High-Performance Superconducting YBCO Films

“…The technologies to grow YBCO thin films can be divided into physical and chemical methods. On the one hand, vacuum methods comprise the most widely studied techniques like pulsed laser deposition (PLD) [4], physical vapor deposition (PVD) [5] and metal-organic chemical vapor deposition (MOCVD) [6,7]. They require ultra-high vacuum systems, which raise the production costs and cause difficulties in scaling up the length of the process.…”