Electromagnetic Properties of Thick Film REBCO Tapes

RE-Ba-Cu-O (REBCO, RE = rare earth) coated conductors are characterized by an anisotropic pinning behavior in applied magnetic fields. Over the years, incorporation of BaZrO3 nanocolumns has been an effective approach to improve the pinning force and reduce the anisotropy in these materials. In this paper, the magnetic field dependence of critical current density (J_c) of 4.7 μm thick films grown by advanced metal-organic chemical vapor deposition (A-MOCVD) with 5% and 15% Zr addition has been studied. At 65 K, 1.5 T, the 5% Zr-added thick films manifest a J_c at H||c-axis that surpasses 3 MA/cm². Increasing the Zr content to 15% results in a plateau in J_c from 0.4 to 6.5 T and enables higher values of J_c at fields above 6 T at 65 K. Tapes with 15% of added Zr exhibit a lift factor in critical current density (J_c (Temperature, Applied Magnetic Field) / J_c (77 K, 0 T)) exceeding 13 and a J_c exceeding 11 MA/cm² at 30 K, 3 T.

I. Introduction

Rebco (RE–Ba–Cu–O, RE = rare earth) conductors have strong potential for use in high power and high magnetic field applications [1]. These applications include power transmission, magnets, energy storage and renewable energy [2]–[4]. In recent years, there have been tremendous efforts to improve the performance of REBCO conductors to meet the applications requirements. One main requirement is to increase the engineering critical current density which can be met by reducing the thickness of the superconducting film or by reducing the thickness dependence of the critical current [5]–[7] as well as reducing the magnetic field anisotropy through the introduction of artificial pinning centers [8], [9]. Perovskite oxides BMO₃ (B: Ba, M: Hf, Sn, Zr etc) form self-assembled nanorods when introduced in the REBCO matrix primarily along the c-axis of the REBCO film. These nanorods act as strong pinning centers when the magnetic field is aligned near the c-axis at high temperatures (65 K–77 K) leading to an increase of the critical current in this direction [9]. Besides, point defects resulting from the lattice mismatch between the nanorods and the REBCO matrix improve the pinning at all field directions in the weak pinning regime (below 40 K) [10]. The efficiency of the BMO₃ artificial pinning centers is directly related to their size, density and continuity [11]. These characteristics are controlled by the growth conditions, deposition temperature, growth rate and dopant density [11].