Generating mixed morphology BaZrO₃artificial pinning centers for strong and isotropic pinning in BaZrO₃–Y₂O₃double-doped YBCO thin films

Abstract

High concentration artificial pinning centers (APCs), such as BaZrO3 nanorods (BZO 1D APCs) aligned along the c-axis of the high temperature superconductor YBa2Cu3O7 (YBCO) can provide strong pinning of magnetic vortices and are desirable for applications in high magnetic fields. Unfortunately, in YBCO films with single-doping (SD) of BZO 1D APCs, a monotonic decreasing superconducting Tc and critical current density Jc(H) with BZO doping has been observed due to strain field overlap at high-concentration perfectly c-axis aligned BZO 1D APCs. In order to resolve this issue, double-doping (DD) of 2–6 vol% BZO 1D APCs and 3.0 vol% Y2O3 nanoparticles (Y2O3-NPs) in YBCO films has been explored to promote BZO-NR orientation misalignment from the c-axis. Remarkably, a monotonic increasing Jc(H) with BZO 1D APCs concentration has been obtained in the BZO DD samples. Such a microstructure change is evidenced in the much smaller c-lattice parameter expansion of 0.103% in the DD samples as opposed to 0.511% in the SD counterparts and reduced c-axis alignment of the BZO 1D APCs as revealed in TEM. This yields a mixed 1D + 2D + 3D APC morphology and enhanced isotropic pinning with respect to the orientation of the H-field in the BZO DD samples.

Overcoming optimization constraint for J c by hybrid pinning in YBa2Cu3O7 films containing nanorods

“…Recently, the hybrid pinning consisting of multiple types of pinning centers has been investigated for further control of vortex pinning, [21][22][23][24][25] where combination of nanorods and nanoparticles is one of the most effective hybrid pinning systems. In the YBCO tapes containing BSO nanorods and Y 2 O 3 nanoparticles, the nanorods have worked as strong c-axis correlated pinning centers to mainly determine J c for B//c, while the nanoparticles have improved the J c in high magnetic field and suppressed the J c anisotropy.…”

The benefit of Ca in improving pinning of BaZrO3-Y2O3doubly-doped YBa2Cu3O7-x/Ca0.3Y0.7Ba2Cu3O7-xmultilayer nanocomposite films

“…Jha et al reported reduced J c anisotropy from 180% to 80% with 3 areal% of Y 2 O 3 and 3 vol.% BSO concentrations in YBCO as compared to its singly-doped (SD) counterpart (with BSO only) at 65 K and 1 T [15]. Similarly, Chen et al observed reduced anisotropy in BZO + Y 2 O 3 DD films of varying BZO concentrations of 2-6 vol.% and 3 vol.% of Y 2 O 3 [4]. J c anisotropy as low as 18% has been observed at 65 K and 9 T by Gautam et al in YBCO DD films containing 2 vol.…”

“…The c-axis-aligned one-dimensional artificial pinning centers (1D-APCs), such as nanorods of BaZrO 3 (BZO), BaSnO 3 (BSO), BaHfO 3 (BHO), and YBa 2 (Nb/Ta)O 6, in high temperature superconducting (HTS) REBaCu 3 O 7-x (RE = Y, Gd, Sm) films provide strong correlated pinning at B//c-axis [1][2][3][4][5][6][7][8][9][10]. However, the strain field originated from the lattice mismatch at the 1D-APC/REBCO interface could result in reduced superconducting transition temperature (T c ) and critical current density (J c ) at temperatures close to T c [11][12][13][14].…”

“…Both DD-ML and DD-SL samples have a fixed 3 vol.% of Y 2 O 3 doping (with −4% lattice mismatch with YBCO), while the BZO (with +7.7% lattice mismatch with YBCO) concentration was varied to 2, 4 and 6 vol.%, while previous studies have only examined the ML approach in BZO-doped YBCO films without Y 2 O 3 [27][28][29][30][31]. Many studies have been conducted on DD-SL YBCO films with the goal of enhancing J c and angular isotropic J c through the use of mixed APCs [4,6,15,20,21,32,33]. These investigations have focused on improving the pinning properties of the films, which is crucial for maximizing the performance of high-temperature superconductors.…”

Temperature dependent pinning efficiency in multilayer and single layer BZO/YBCO nanocomposite films

“…Various APCs of different morphologies, including c-axis aligned one-dimensional nanorods (1D-APCs), ab-plane aligned twodimensional planar defects (2D-APCs), and three-dimensional nanoparticles (3D-APCs) have been reported through the addition of secondary dopants like BaZrO 3 (BZO), BaHfO 3 (BHO), BaSnO3 (BSO), YBa2(Nb/Ta)O6, Y2O3, etc. in YBCO (or other rare-earth variation of YBCO) to form APC/YBCO nanocomposites films [7][8][9][10][11][12][13][14][15].…”