Iridium: an oxygen diffusion barrier and a conductive seed Layer for RABiTS-based coated conductors

For power applications of YBa₂Cu₃O_7-δ (YBCO) coated conductors, it is necessary to electrically stabilize the conductor. An economic way to achieve this, which also benefits the engineering J_E, is to grow conductive buffer layers directly on textured Cu or Ni metal surfaces. However, due to poor oxidation resistance and high reactivity/diffusivity of Cu or Ni, an insulating oxide layer usually forms at the metal/substrate interface, degrading the electrical connectivity of the entire architecture. To overcome this problem, we have developed a new conductive, nonmagnetic buffer layer architecture of La_0.7Sr_0.3MnO₃/Ir on textured Ni-based tapes. This structure serves as a barrier to both inward diffusion of oxygen and outward diffusion of metal cations. Using PLD to grow YBCO, we demonstrate ideal electrical coupling to the metal substrate. Critical current (I_c) values for 1 μm thick YBCO coatings exceed 100 A/cm-width at 77 K on a Ni-W RABiTS template.