Single Crystal Growth and Characterization of Thallium Cuprate Superconductors — A Review

We review the single crystal growth and characterization of thallium cuprate superconductors. Reasonably large crystals (several mm size) have been grown by self-flux technique and KCl-flux methods. The anisotropic resistivities Pab (along ab-plane) and Pc (along c-axis) were measured for all double-Tl-O compounds by Montgomery method. Pc is found to be 2 orders of magnitude greater than Pab for all of these samples. Hence, these systems have high anisotropy. The paraconductivity data shows that Tl-2201 is a two-dimensional superconductor whereas Tl-2212 has a two-dimensional behavior at higher temperatures and some samples showed crossover from two-dimensional to three-dimensional at 6 degrees above Tc of 101 K. Hall data, annealing effects on different Tl systems, irradiation effects and pressure dependence of Tc are reported.