The RABiTS approach: Using rolling-assisted biaxially textured substrates for high-performance YBCO superconductors

This article provides an overview of the fabrication of epitaxial, biaxially aligned buffer layers on rolling-assisted biaxially textured substrates (RABiTS) as templates for YBCO films carrying high critical current densities. The RABiTS technique uses standard thermomechanical processing to obtain long lengths of flexible, biaxially oriented substrates with smooth surfaces. The strong biaxial texture of the metal is conferred to the superconductor by the deposition of intermediate metal and/or oxide layers that serve both as a chemical and a structural buffer. Epitaxial YBCO films with critical current densities exceeding 3 x 10(6) A/cm(2) at 77 K in self-field have been grown on RABiTS using a variety of techniques and demonstrate magnetic-field-dependent critical current values that are similar to those of epitaxial films on single-crystal ceramic substrates. The RABiTS architecture most commonly used consists of a CeO2 (sputtered)/YSZ (sputtered)/Y2O3 (e-beam)/Ni-W alloy. The desired texture of the base metal has been achieved in 100 m lengths and >10 cm widths. Scaleable and cost-effective techniques are also being pursued to deposit the epitaxial multilayers. The results discussed here demonstrate that this technique is a viable route for the fabrication of long lengths of high-critical-current-density wire capable of carrying high currents in magnetic fields and at temperatures accessible by cooling with relatively inexpensive liquid nitrogen (up through the 77 K range).