Iridium: An oxygen diffusion barrier and a conductive seed layer for RABiTS-based coated conductors

For power applications of YBa2Cu3O7-delta (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 La0.7Sr0.3MnO3/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 mu m thick YBCO coatings exceed 100 A/cm-width at 77 K on a Ni-W RABiTS template.