Iridium: an oxygen diffusion barrier and a conductive seed Layer for RABiTS-based coated conductors
For power applications of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) coated conductors, it is necessary to electrically stabilize the conductor. An economic way to achieve this, which also benefits the engineering J/sub 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/sub 0.7/Sr/sub 0.3/MnO/sub 3//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/sub c/) values for 1 /spl mu/m thick YBCO coatings exceed 100 A/cm-width at 77 K on a Ni-W RABiTS template.