Title :
Effect of oxygen over-doping on T/sub c/ and R/sub s/ of YBCO films
Author :
Gavaler, J.R. ; Talvacchio, J. ; Weinert, R.W.
Author_Institution :
Sci. & Technol. Center, Westinghouse Electr. Corp., Pittsburgh, PA, USA
fDate :
6/1/1995 12:00:00 AM
Abstract :
Data on bulk YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) have shown that optimum critical temperatures are obtained in material that has less than the maximum (stoichiometric) oxygen content, x=0. We have prepared films of YBCO that were over doped with oxygen and have measured their properties. In some of these films, T/sub c/´s were degraded to as low as 85 K and R/sub s/´s to >10 m/spl Omega/ (at 77 K and 10 GHz). Re-annealing at 450/spl deg/C at experimentally optimized oxygen pressures raised T/sub c/´s significantly in all cases but had only a marginal effect on R/sub s/ values. Large improvements in R/sub s/ were obtained in the films which initially had very high surface resistances only by annealing them at higher temperatures. Growth and annealing conditions are described by which YBCO films with T/sub c/´s of >90 K and R/sub s/´s of /spl les/0.5 m/spl Omega/ (at 77 K and 10 GHz) were prepared.<>
Keywords :
annealing; barium compounds; high-temperature superconductors; sputter deposition; superconducting thin films; superconducting transition temperature; surface conductivity; yttrium compounds; 0.5 to 10 mohm; 10 GHz; 450 C; 77 K; 85 to 90 K; O over-doping; YBa/sub 2/Cu/sub 3/O/sub 7/; annealing; high temperature superconductor; surface resistance; thin films; transition temperature; Annealing; Argon; Conductivity; Degradation; Oxygen; Scanning electron microscopy; Superconducting films; Surface resistance; Temperature measurement; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
