Superconducting Thallium Oxide and Mercury Oxide Films

Previously we reported on a two-layer electrodeposition process of thallium oxide superconductors that showed transport critical current density above 106 A/cm2 at 77 K in zero field. In this article, we report our effort to convert an electrodeposited thick film of (Tl,Bi,Pb)2(Sr,Ba)2Ca1Cu2Ox to (Hg,Bi,Pb)2(Sr,Ba)2Ca1Cu2Ox by the cation-exchange process. We are also reporting magneto-opticalimaging data on Tl oxide superconductor films, which are compared with YBCO. Magneto-optical imaging provides insight into the nature of current flow in the Tl oxide superconductor, and thus, will help us to improve the critical current density in bulk high-temperature superconductor wire or tape.