Effect of the Grain-boundary Misorientation Distribution on the Intergranular Voltage Relaxation of Bi1.65Pb0.35Sr2Ca2Cu3 O (10+delta) Ceramic Samples

Normalized-intergranular-power-dissipation — Normalized intergranular power dissipation maps predicted by the model described in Section 2.3. The maps were obtained by using the GBMD displayed in Fig. 1 for samples BP2 ((a) and (c)) and BP5 ((b) and (d)). The intergranular power dissipation maps (IPDM) represent snapshots at different computational times: t = 60 ((a) and (b)) and t = 80 ((c) and (d)). The color scale goes from light-green to red: the light-green color identifies the superconducting regions, and red regions represents the full power dissipation (regions in normal state)

Writers: E. Govea-Alcaide; I. García-Fornaris; P. A. Suzuki; R. F. Jardim

Keywords: Bi-based cuprates; Grain boundaries Misorientation distribution; Transport relaxation

Abstract: The impact of the grain boundary misorientation distribution (GBMD) on the intergranular voltage relaxation (V − t) curves at zero applied magnetic field in Bi_1.65Pb_0.35Sr₂Ca₂Cu₃O_10+δ(Bi-2223) ceramic samples has been investigated. Changes in the GMBD were realized by subjecting powders of Bi-2223 to two different uniaxial compacting pressures (UCP) before the last heat treatment of the samples. The GBMD was then determined from X-ray rocking curves and revealed significant differences between intergranular media of the specimens. It was found that the UCP results in a two-time reduction in the population of high-angle grain boundaries (𝜃 > 12^∘) while the orientation homogeneity of the grain boundaries rises ∼ 30 %, indicating an improvement of the degree of texture of the materials. Such changes are mirrored in the behavior of the V − t curves which are explained by invoking differences in the rearrangement of the transport current driven by the angular dependence of the critical current density along grain boundaries. Numerical simulations of the V − t curves support the experimental V − t results and further suggest the occurrence of current localization in conductive paths within the materials.