The Effect of Recrystallization of Fine Inclusions on the Enhancement of Flux Pinning in Textured Gd-Ba-Cu-O Bulk Superconductors

Well textured GdBa₂Cu₃O_7-δ single domain bulks have been prepared successfully. Based on these samples, dilute impurities doping for the enhancement of flux pinning has been investigated. To achieve the fine inclusion particles, except ball milling process, a possible recrystallization mechanism is proposed. BaTiO₃ powder was synthesized as dopant. BaO₂ doping and mixed BaO₂ and TiO₂ doping were performed as references. The recrystallization mechanism was studied by means of the evolution of flux pinning behaviors along the growth direction of the successfully textured single domain bulks. BaTiO₃ retains a semi-melting state in the harsh ambient of the melting process. The state was assumed like a colloidal droplet, which can be divided into more than one smaller fragment by the anisotropic growth of matrix. This hypothesis was studied in the sample, which was grown at a lower initial growth temperature. The evolution of flux pinning behaviors along the c-axis shows a remarkable increase of the critical current density under low field together with the decreased peak effect. The increased low-field pinning strength is partially attributed to the recrystallization of the BaTiO₃ doping related fine precipitations.