Effect of Na substitution on superconducting properties of Bi-2212 ceramics prepared by Sinter-Forged process

Bulk textured Bi2Sr2Ca1−xNaxCu2Oy (x = 0.0, 0.05, 0.075 0.1, 0.15, and 0.20) ceramics have been prepared by a polymer solution method followed by sinter-forging process. The microstructure and superconducting properties of textured samples were affected by Na substitution. According to XRD data, all samples show that Bi-2212 phase is the major one, and main peaks corresponded to the (00ℓ) diffractions confirming that the crystallographic c-axis is perpendicular to the surface. SEM micrographs showed that samples are composed of well-stacked and oriented grains. The best critical temperature, TC, was measured as 85.6 K for x = 0.075. The critical current density Jc, values decrease gradually with the increase of applied magnetic field. The maximum calculated Jc was 1.38 × 105 A/cm2 at 10 K for 0.075 Na sample which is about four times higher than the 0.34 × 105 A/cm2 value determined for the pure sample. The anisotropic properties of these textured materials have been investigated using magnetic measurements.