Replacement of NbN by YBa2Cu3O7-delta in superconducting thin film coil in a spiral trench on a Si-wafer for compact SMESs

To improve the energy storage volume density of our concept of a compact superconducting magnetic energy storage system, replacement of superconducting material NbN for the thin film coil in the spiral trench on a Si wafer by a high temperature superconductor YBa2Cu3O7-delta was addressed. By using the successful result previously reported to grow a c-axis oriented film on a steel substrate, a superconducting film of T-c=45.5 K was obtained using similar buffer layers including a (100) oriented CeO2 layer over a (100) oriented YSZ layer. The similar result reported on a SrTiO3 single crystal substrate without any buffer layers indicates c-axis oriented film of Tc=90K can be obtained by further reduction of oxygen partial pressure.