Epitaxy of HgBa2CaCu2O6 superconducting films on biaxially textured Ni substrates

Superconducting HgBa2CaCu2O6 (Hg-1212) films have been coated on biaxially textured Ni substrates buffered with CeO2/YSZ/CeO2 trilayers. A two-step cation-exchange process was employed for Hg-1212 coatings, whereby epitaxial Tl2Ba2CaCu2O8 precursor films grown in a fast temperature ramping annealing process were converted to Hg-1212 via diffusive Hg-Tl cation exchange. This minimizes chemical diffusion/reaction of Hg with the substrates and allows Hg-1212 films to inherit the epitaxy and smooth surface morphology of the Tl2Ba2CaCu2O8 precursor films. The superconducting transition temperature (T-c) of these Hg-1212 coated conductors is up to 124 K. Self-field critical current densities (J(c)) of 2.2x10(6) A/cm(2) at 77 K have been obtained, with J(c) values of 0.7x10(6) A/cm(2) achieved at 100 K. These results show Hg-1212 coated conductors may hold promise for electrical power applications above 77 K. (C) 2000 American Institute of Physics. [S0003-6951(00)05151-2].