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

Volume

5

Issue

2

fYear

1995

fDate

6/1/1995 12:00:00 AM

Firstpage

1173

Lastpage

1176

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;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.402770

Filename

402770