Title :
Microstructural changes in TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// thin films after reducing anneals which enhance critical current density
Author :
Newcomer, P.P. ; Siegal, M.P. ; Venturini, E.L. ; Morosin, B. ; Overmyer, D.L.
Author_Institution :
Sandia Nat. Labs., Albuquerque, NM, USA
fDate :
6/1/1997 12:00:00 AM
Abstract :
Microstructural changes in TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// (Tl-1212) epitaxial thin films resulting from low oxygen partial pressure furnace anneals at 600/spl deg/C are studied using high resolution transmission electron microscopy (TEM). These post-growth anneals have been shown to significantly raise the superconducting transition temperature from 70 to 90 K, and greatly improve the magnetic flux pinning and the critical current density. Changes occur in both the microstructure and the morphology of the films that correlate with changes in J/sub c/. Plan view TEM and high-resolution cross-sectional TEM analysis of the films before and after anneals demonstrates changes in the lattice fringe image, overall contrast modulation, and nanometer-scale discontinuities.
Keywords :
annealing; barium compounds; calcium compounds; critical current density (superconductivity); crystal microstructure; flux pinning; high-temperature superconductors; superconducting epitaxial layers; superconducting transition temperature; thallium compounds; transmission electron microscopy; 600 C; 90 K; Tl-1212 thin films; TlBa/sub 2/CaCu/sub 2/O/sub 7-/spl part// epitaxial thin films; TlBa/sub 2/CaCu/sub 2/O/sub 7/; contrast modulation; critical current density enhancement; high resolution transmission electron microscopy; high-resolution cross-sectional TEM analysis; lattice fringe image; low O/sub 2/ partial pressure furnace anneals; magnetic flux pinning; microstructural changes; morphology; nanometer-scale discontinuities; plan view TEM; post-growth anneals; reducing anneals; superconducting transition temperature; Annealing; Critical current density; Furnaces; Magnetic films; Magnetic flux; Microstructure; Morphology; Superconducting thin films; Superconducting transition temperature; Transmission electron microscopy;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
