Power law behavior of Tl1Ba2Ca2Cu3O9 superconducting tapes

Specimens of Tl1Ba2Ca2Cu3O9 superconducting tapes (Tl-1223) have been prepared using the powder-in-tube (PIT) method. Dissipative mechanisms and power law behavior were investigated using magnetoresistance measurements and I-V characteristics. The temperature and magnetic field dependences of the resistance R(T,B) were fitted to the Arrhenius relation from which the magnetic field dependence of the pinning energy U-0(B) was derived. The I-V data were fitted to a power law expression V similar to I-alpha(T,I-B) in which the exponent a was found to decrease gradually with increase of temperature and magnetic field. The variations of the critical current densities with applied magnetic field J(c)(B) were also studied. The correlation of the pinning energy to the critical current density was attempted. These results are discussed and explained in terms of the thermally activated flux flow (TAFF), grain boundaries, weak links, and Josephson junctions between the grains.