Title :
Effect of Ca-doping on grain boundaries and superconducting properties of YBa2Cu3O7-δ
Author :
Berenov, Andrey V. ; Marriott, Roger ; Foltyn, Steven R. ; MacManus-Driscoll, Judith L.
Author_Institution :
Dept. of Mater., Imperial Coll. of Sci., Technol. & Med., London, UK
fDate :
3/1/2001 12:00:00 AM
Abstract :
It is well known that the properties of grain boundaries in YBa 2Cu3O7-δ films differ drastically from bulk material. It has been shown both experimentally and theoretically that the grain boundaries in YBa2Cu3O7-δ superconductors are depleted of carriers as compared to the bulk. This depletion leads to weak intergrain links and limits critical currents in the superconductor. Recently, the promise for improved grain boundaries has been shown in Ca-doped YBa2Cu3O7-δ thin films and in Ca doped YBa2Cu3O7-δ biaxial grain boundaries. In this study, the effect of Ca-doping of grain boundaries in YBa2Cn3O7-δ films and bulk have been investigated in an attempt to increase the hole concentration at the grain boundaries and to improve Jc. Ca-gels were applied to sintered YBa2Cu3O7-δ pellets and thin films. High temperature post-anneals were used to diffuse Ca preferentially into the grain boundaries. The distribution of Ca in the samples was studied by secondary ion mass spectrometry (SIMS). The effect of Ca-doping on TC and JC was studied by VSM. In epitaxial thin films increased JC were found at 40 K, but not at 77 K
Keywords :
annealing; barium compounds; calcium; critical current density (superconductivity); grain boundaries; grain boundary diffusion; high-temperature superconductors; hole density; secondary ion mass spectra; superconducting epitaxial layers; superconducting thin films; superconducting transition temperature; yttrium compounds; 40 to 77 K; Ca-doped YBa2Cu3O7-δ thin films; Ca-doping; Ca-gels; Jc; SIMS; TC; VSM; YBa2Cu3O7-δ; YBa2Cu3O7:Ca; biaxial grain boundaries; critical currents; epitaxial thin film; films; grain boundaries; high temperature post-anneals; hole concentration; secondary ion mass spectrometry; sintered YBa2Cu3O7-δ pellets; superconducting properties; thin films; weak intergrain links; Annealing; Doping; Grain boundaries; High temperature superconductors; Superconducting epitaxial layers; Superconducting films; Superconducting materials; Superconducting thin films; Superconductivity; Transistors;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
