Superconducting thallium oxide and mercury oxide films

This paper reports on a study to convert electrodeposited Tl-oxide films to Hg-1212 using the cation-exchange process. A two-layer electrodeposition process was used to prepare Tl-Ba-Ca-Cu-O films with Tl-1212 and Tl-2212 stoichiometry. Electrodeposited Tl-films were also deposited with Bi and Sr substituted for the Tl and Ba, respectively and also reacted using cation exchange to attempt formation of Hg-1212. The superconducting transition temperature for the "non-substituted" films improved from 97 to 120 K after the cation-exchange process with a critical current density exceeding 2 x 10(6) at 5 K in zero field. The cation-exchange process for the Bi, Sr substituted films appears to be more difficult with no marked improvement in superconducting properties. (C) 2001 Elsevier Science B.V. All rights reserved.