CRITICAL-CURRENT AS A FUNCTION OF FILM THICKNESS FOR SPRAY PYROLYZED FILMS OF TLBA2CA2CU3OY

It is imperative for tape applications to produce thicker films of TlB a2Ca2Cu3Oy with high critical current density on polycrystalline subst rates (a useful figure of merit is the critical current per unit width , with a reasonable goal being 10 A mm(-1)). We have studied the criti cal current density at 77 K, 0 T (J(c)) as a function of film thicknes s in the range 2 to 10 mu m. A key parameter for obtaining a high J(c) was found to be the film density; firms with relative density > 82% s howed much higher values of J(c). Based on average values, J(c) was fo und to peak at 60 kA cm(-2) for samples 2.5 to 5 mu m thick (correspon ding to 3 A mm(-1) for 5 mu m thick samples), and to decrease for thic ker samples, yielding 3 to 3.5 A mm(-1) from 5 to 10 mu m There are in dividual segments with values as high as 8.4 A mm(-1).