Synthesis and properties of Tl-Ba-Ca-Cu-O superconductors

We review the synthesis methods and properties of single crystal, powder, and thin film T1BaCaCuO high-temperature superconducting (T1-HTS) materials. With transition temperatures greater than or equal to 100 K for several compounds, T1-HTS materials present real opportunities for applications above 77 K. Experiments using (1) single crystals: determined precise structural parameters and identified the complex T1(1+)-T1(3+) equilibrium model; (2) powders: studied the complex thermodynamic phase diagram; and (3) epitaxial films: studied fundamental properties such as electron pair symmetry and the effect of controlled extrinsic defects on flux pinning strength, as well as providing the large-area surfaces required for device applications.