LOW-TEMPERATURE FORMATION OF EPITAXIAL TL2CA2BA2CU3O10 THIN-FILMS IN REDUCED O2 PRESSURE

Epitaxial Tl2Ca2Ba2Cu3O10 films on (100) LaAlO3 are prepared by post-annealing 2Tl:2Ca:2Ba:3Cu precursor films at 830-860-degrees-C in congruent-to 0.03-0.15 atm of O2. These films (0.2-1.1-mu-m thickness) are smooth and shiny to the eye, and have a sharp zero resistance and onset diamagnetic transition temperature of 117-121 K. Transport critical current densities of 1.6 x 10(6) A/cm2 at 77 K and congruent-to 10(5) A/cm2 at 100 K are obtained for a 0.38-mu-m-thick film in magnetic fields up to 100 Oe. Strong flux pinning at low temperatures is inferred from the weak-field dependence of the critical current density calculated from magnetic hysteresis loops. At 5 K, the best film has a magnetic critical current density of 9 x 10(6) A/cm2 in zero field, decreasing gradually to 1.5 x 10(6) A/cm2 in a 5-T field.