Improved Flux Pinning Performance of GdBCO Superconductor Bulks by Gd3ZrO7 Additions.

Four GdBa₂Cu₃O_7-β (GdBCO or Gd₁₂₃) superconductor bulks doped with different amounts of Gd₃ZrO₇ particles have been successfully prepared by the modified top-seeded melt-texture growth. Superconducting properties and microstructures of these bulks have been investigated in detail. All GdBCO bulks exhibit superior superconductivity with the onset critical temperature (Tc;onset) above 94 K, and the highest critical current density (J_c) of 49.1 kA/cm² was obtained in the GdBCO bulk doped with 0.8 mol.% Gd₃ZrO₇ particles at 77 K in self-field. During the top-seeded melt-texture growth process, the Gd₃ZrO₇ additions can react with the GdBCO phase, forming the BaZrO3 particles and intensifying the Gd/Ba substitution, which can improve the flux pinning performance of the GdBCO bulk. As a result, J_c was enhanced and the trapped flux density significantly increased with the increase of Gd₃ZrO₇ additions. The maximum trapped flux density of 0.56 T obtained in the GdBCO bulk with 0.8 mol.% Gd₃ZrO₇ additions is more than three times as high as that of the undoped bulk. The squared stripes around the seed crystal were found in the doped bulks, and were identified as the macroscopic appearance of inhomogeneous microstructure in which the Gd₂BaCuO₅ (Gd₂₁₁) free region and the Gd₂₁₁-containing region were separated by a BaZrO3-and-Ag layer in a small region. But such microstructural inhomogeneity can be well improved with the increase of Gd₃ZrO₇ additions. All these results show that Gd₃ZrO₇ additions improve the pinning performance of GdBCO superconductor bulks. [ABSTRACT FROM AUTHOR]