High quality YBa2Cu3O7 films on polyalumina

Superconducting YBCO (YBa2Cu3O7) films were deposited on polycrystalline alumina substrates with c-normal orientation. YBCO films deposited directly on alumina exhibited a broad transition with Tc, zero=60 K. The Tc, zero increased to 86 K upon the use of a YSZ (yttria stabilized zirconia) buffer layer to stop the interface reaction. However, the Jc of these films was still below 104 A/cm2. A simple surface modification of the polycrystalline alumina substrate by way of depositing a YSZ buffer and repolishing the surface drastically improved the Jc. Values of 104 A/cm2 observed at 30 K is the best Jc reported so far for YBCO films on polycrystalline alumina. We believe further improvements in both the surface finish of the polyalumina and the YSZ buffer layer will lead to microwave quality YBCO films on polyalumina.