Improved flux pinning in YBa₂Cu₃O₇with nanorods of the double perovskite Ba₂YNbO₆

Abstract

We report significantly enhanced critical current densities (J c ) and flux pinning forces (F p ) in applied magnetic fields for YBa 2 Cu 3 O 7 (YBCO) films with embedded Ba 2 YNbO 6 (BYNO) nanorods. The films were grown by pulsed laser deposition with a target consisting of YBa 2 Cu 3 O y with five molar per cent additions of BaNbO y and Y 2 O 3 . With this composition, deposited films were found to contain a high density of BYNO nanorods that frequently traversed the entire thickness of the film (up to 1 μm), depending upon the deposition conditions. Enhanced J c performance occurs primarily for applied field orientations near the c-axis of the YBCO, which is nominally along the growth direction of the BYNO nanorods. The threading nanorod density of one film of the present work was measured by plan-view transmission electron microscopy to be 710-850 nanorods μm −2 . For approximately 1 μm thick films, typical J c (75.6 K, sf) and J c (75.6 K, 1 T c) values were ∼4.5 MA cm −2 and 1.3-1.5 MA cm −2 , respectively. For a 0.5 μm thick film, J c (75.6 K, 1 T c) > 2 MA cm −2 was achieved, and values of F p in excess of 30 and 120 GN m −3 were achieved at 75.5 K and 65 K, respectively.

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.…”

Enhanced flux pinning in MOD-YBCO films with co-doping of BaZrO3 and Y2O3 nanoparticles

“…to obtaining significant improvements in J c have been realized for YBCO films, including decoration of substrate surfaces by nanoparticles [2][3][4][5], the addition of oxide nanoparticles [6][7][8][9], multilayering of YBCO with second-phase materials [10][11][12], mixed rare-earth elements doping [13][14][15], and an intentional deviation from the 123 stoichiometry [16,17]. Among these strategies for the enhancement J c of YBCO films, introduction of nanoparticles in YBCO films is the most promising approach for its valuable advantages such as high efficiency and easy control.…”

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

“…[3][4][5][6][7] High critical current densities are being pursued in REBCO superconducting tapes in high magnetic fields (2-30 T) in a temperature range of 4.2 K-50 K for use of these materials in electric power applications such as motors, generators, superconducting magnetic energy storage (SMES) as well as in high energy particle accelerators, magnetic resonance imaging, and high-field magnets. Introduction of Y 2 BaCuO 5 , 8 BaZrO 3 (BZO), [9][10][11][12][13] BaSnO 3 ,14,15 BaHfO 3 , 16 Ba 2 YNbO 6 , 17,18 and Gd 3 TaO 7 19 nanoscale defects in the REBCO films of the superconducting tapes has been proven to be a powerful method to increase critical current density (J c ) of these tapes via enhanced flux pinning by these defects. Until recently, high J c in REBCO films with BaMO 3 (M ¼ Zr, Sn, and Hf) nanoscale defects has been obtained only with less than 10 mol.…”