Doping Effect on Partial-Melting of Hg _x Ba₂Ca₂Cu₃Re_0.2O _y Filament

Abstract

We have studied the fabrication of filamentary Fig system superconductor using a solution spinning method with Re addition. A controlled vapor/solid reaction process is necessary for preparing Hg-based superconductor by this method. As the F-doping resulted in a dense liquidus texture, F and Cl doping effects on partial-melting of filamentary Hg _x Ba₂Ca₂Cu₃Re_0.2O _y superconductor are examined to enhance the J _c and to reduce the inciting temperature. A filamentary Ba₂Ca₂Cu₃Re_0.2O _y precursor was spun by a solution spinning method and partially melted in an evacuated quartz tube with a pellet as a reactor. Hg₁Ba_1.8Ca₂Cu₃Re_0.2(BaF₂)_0.2O _y , Hg_0.8Ba_1.8Ca₂Cu₃Re_0.2(BaF₂)_0.2O _y , Hg₁Ba₂Ca₂Cu_2.8Re_0.2(CuF₂)_0.2O _y , Hg_0.925Ba₂Ca₂Cu₃Re_0.2(HgCl₂)_0.075O _y and Hg_0.8Ba_1.8Ca₂Cu₃Re_0.2(BaF₂)_0.2(HgCl₂)_0.03O _y pellets were prepared by a two-step solid state reaction method.

The partial-inelting temperature of the filamentary sample reacted with Hg₁Ba₂Ca₂Cu_2.8Re_0.2(CuF₂)_0.2O _y pellet was lower than others. The texture of the filamentary sample was dependent on the vaporizing materials. The J _c of the sample was enhanced by post-annealing up to 350 °C in O₂ flow. By controlling the heating condition, a high J _c value more than 10⁴ A/cm² at 77 K and 0 T was attained for both F and Cl doped sample.