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

Abstract

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 Tc of pure YBa2Cu3−xAgxO7−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 (Jc) 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 YBa2Cu3−xAgxO7−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.