A multistep postannealing scheme has been developed for preparing nearly single phased, c-axis oriented TlBa2Ca2Cu3Ox (Tl-1223) superconducting thin films fabricated by the direct-current-sputtering process. Films obtained by the present process have shown, for the first time in this system, a critical current density (Jc) above 106 A/cm2 at 77 K with a zero-resistance transition temperature Tc0≊110 K. The order of magnitude enhancement in Jc is attributed to the improvement of film morphology which, in turn, removed most of the weak links encountered previously.

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