| Summary: | We have made detailed current-voltage (I-V) studies of a Tl-1223/Ag tape. Although the tape has a fairly high self-field critical current density J(c) at 77 K (similar to 5 x 10(7) A/m(2)), the I-V characteristics display the "weak-link" signatures well-known for YBa2Cu3O7: linear dissipation above a sharply-defined critical current, pronounced decrease of J(c) in a magnetic field H, and hysteresis with respect to field cycling. Encouragingly, there is evidence too that at high fields, a few strongly-linked current paths, composed of textured grains, do survive. Implications for the superconductive behaviour of grain boundaries are discussed.
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