Critical current as a function of film thickness for spray pyrolyzed films of TlBa2Ca2Cu3Oy

Abstract It is imperative for tape applications to produce thicker films of TlBa 2 Ca 2 Cu 3 O y with high critical current density on polycrystalline substrates (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 critical current density at 77 K, 0 T ( J c ) as a function of film thickness in the range 2 to 10 μm. A key parameter for obtaining a high J c was found to be the film density; films with relative density > 82% showed much higher values of J c . Based on average values, J c was found to peak at 60 kA cm −2 for samples 2.5 to 5 μm thick (corresponding to 3 A mm −1 for 5 μm thick samples), and to decrease for thicker samples, yielding 3 to 3.5 A mm −1 from 5 to 10 μm. There are individual segments with values as high as 8.4 A mm −1 .