HIGH-QUALITY YBA2CU3O7 FILMS ON POLYALUMINA

Superconducting YBCO (YBa2Cu3O7) films were deposited on polycrystalli ne alumina substrates with c-normal orientation. YBCO films deposited directly on alumina exhibited a broad transition with T(c, zero) = 0 K . The T(c, zero) increased to 86 K upon the use of a YSZ (yttria stabi lized zirconia) buffer layer to stop the interface reaction. However, the J(c) of these films was still below 10(4) A/cm2. A simple surface modification of the polycrystalline alumina substrate by way of deposi ting a YSZ buffer and repolishing the surface drastically improved the J(c). Values of 10(4) A/cm2 observed at 30 K is the best J(c) reporte d so far for YBCO films on polycrystalline alumina. We believe further improvements in both the surface finish of the polyalumina and the YS Z buffer layer will lead to microwave quality YBCO films on polyalumin a.