Growth and Optimization of High-Performance Thick Rebco Films for Application over a Wide Range of Temperature (77 - 4.2) K and Magnetic Fields (0 – 15) T

Rare Earth Barium Copper Oxide (REBCO) coated conductors are the only superconductors with a potential for applications over broad range of temperature (77 K – 4.2 K) and wide range of fields (0 – 20 T and above). However, its high cost compared with other available superconductors is a major bottleneck in realizing its desired potential and wide range of applicability. Reducing cost of REBCO in terms of ($/kA-m) can be accomplished by further improving the engineering current density (Je) of these superconductors and reducing the manufacturing cost. Je can be improved in two different ways - by incorporating pinning centers and by increasing thickness (> 2 μm) without deterioration of critical current density (Jc). Increasing pinning centers has a certain limit, after which the critical current degrades. Increasing thickness of REBCO without any deterioration in Jc is a direct way forward to achieving high Je. However, increasing thickness (> 2 μm) of REBCO has always led to decrease in Jc, independent of the deposition method used. The major obstacle here is poor process control, a high Jc could not be maintained along the thickness, while growing thicker films (> 2 μm). In the present work, thick (3.5 -5 μm) undoped and doped REBCO films were grown using an advanced MOCVD (A-MOCVD) reactor. Several different studies have been conducted to optimize compositions in order to achieve high performance for high temperature, low field application with good isotropic behavior and for low temperature, medium - high field applications. Record high Ic of 1440 A/cm at 65 K, 1.5 T (B || c-axis) and a minimum Ic of 1740 A/cm at 65 K, 0.25 T have been attained in 4.7 μm 5 mol% Hf-doped REBCO films. Also, engineering current density (Je) over 5 kA/mm2 (∼ 5X Nb3Sn) has been achieved in a 4.8 μm thick, 15 mol% Zr-doped REBCO at 4.2 K, 14 T ( B parallel to c-axis).