Dependence of the Structural, Electrical and Magnetic Properties of YBa2Cu3O7−δ Bulk Superconductor on the Ag Doping

• Published in: Journal of superconductivity and novel magnetism 2012-07, Vol.25 (5), p.1459-1467
• Main Authors: Yıldız, Aylin, Kocabaş, Kemal, Akyüz, Gönül B.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Critical currents; Cuprates superconductors (high tc and insulating parent compounds); Exact sciences and technology; Magnetic Materials; Magnetism; Original Paper; Physics; Physics and Astronomy; Properties of type I and type II superconductors; Strongly Correlated Systems; Superconductivity; Y-based cuprates
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-012-1482-8

The effects of Ag dopants on the superconducting properties of YBCO bulk samples, prepared under solid-state reaction method, have been studied by resistivity–temperature ( ρ – T ), X-ray diffraction (XRD), scanning electron microscope (SEM), bulk density, AC susceptibility, DC magnetization measurements, and theoretical analysis. Small Ag substitutions ( x ≤0.10) do not effect T c of pure YBa 2 Cu 3− x Ag x O 7− δ , while we observed small decreases of 1.5 K for larger doping levels ( x ≥0.15). AC susceptibility measurements for sintered YBCO pellets have been performed as a function of temperatures at constant frequency and AC field amplitude in the absence of DC bias field. The critical current densities ( J c ) have been estimated as a function of magnetic field from the magnetization data employing Bean’s critical state model. The increase in Ag amount ( x ) in YBa 2 Cu 3− x Ag x O 7− δ ( x ≥0.10) system effectively decreases the intragrain critical current density, which is attributed to the reduced connectivity between the grain boundaries. In the case of small additions ( x =0.05), Ag atoms fill partly the pores, leading better crystallization of the grains.