Title :
Current transport across grain boundaries in TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thick polycrystalline films and YBa/sub 2/Cu/sub 3/O/sub 7/ step edges
Author :
Hettinger, J.D. ; Kim, D.H. ; Miller, D.J. ; Hu, J.G. ; Gray, K.E. ; Sharping, J.E. ; Daly, K. ; Pettiette-Hall, C. ; Tkaczyk, J.E. ; Deluca, J.
Author_Institution :
Argonne Nat. Lab., IL, USA
fDate :
3/1/1993 12:00:00 AM
Abstract :
The authors have performed transport measurements in magnetic fields (H//c) up to 10 T on a series of YBa/sub 2/Cu/sub 3/O/sub 7/ grain boundaries induced by epitaxial growth on a substrate containing a series of step edges. An activation energy which goes as U(T) approximately (1-t) is found. Electric field versus current density curves taken at a constant temperature while varying the magnetic field allows a determination of the magnetic field dependence of the activation energy using the Ambagaokar-Halperin model. These values agree with results extracted from the resistive transitions. Similar characterizations of a sample of TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ are also presented. The temperature dependence of the activation energy for this system may be represented as U(T) approximately (1-t)/sup 2/, suggesting that the grain boundaries behave as SNS (superconducting-normal-superconducting) junctions.<>
Keywords :
barium compounds; calcium compounds; electrical conductivity of crystalline semiconductors and insulators; grain boundaries; high-temperature superconductors; superconducting thin films; thallium compounds; yttrium compounds; Ambagaokar-Halperin model; TlBa/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/; YBa/sub 2/Cu/sub 3/O/sub 7/; activation energy; current transport; epitaxial growth; grain boundaries; high temperature superconductors; step edges; Current density; Epitaxial growth; Grain boundaries; Josephson junctions; Magnetic field measurement; Magnetic fields; Performance evaluation; Substrates; Superconducting epitaxial layers; Temperature dependence;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
