Phase growth and microstructure modifications induced by annealing in highly textured superconducting Bi-2212 thin rods

Abstract

Bi-2212 cylindrical rods were obtained using a laser-induced directional solidification system. Although as-grown Bi-2212 samples are well textured, they do not exhibit superconducting behavior and, as a result, need further heat treatments. The modifications taking place during annealing were analyzed in the present work, in particular with respect to the evolution of the microstructure with the annealing time and the phase content. Diffusion processes in which the Bi-2212 phase grows along the thickness of the platelets take place during annealing. The presented results show that the physical properties of these samples improve during the initial approximately 60 h of annealing and that they remain constant thereafter.

Laser Induced Cylindrical Zone Melting of Bi2Sr2CaCu2O8+∂ Superconductors

“…In addition, a well textured region of approximately 100 µm in thickness is identified in the outer region of the sample (Figure 3-c and -d). This gradient in texture is similar to that reported in planar monoliths processed by PLZM techniques [17,20,21] and in LFZ rods [13,14,18]. This microstructure shows that a planar solidification interface is maintained throughout the external region of the sample.…”

“…This table collects data published in the literature throughout the last decade, which seems reasonable to highlight. The referenced work covers different texturing techniques: LFZ Bi-2212 bars [13,20], electrically assisted LFZ Bi-2212 rods (EALFZ) [21], Bi-2212 rods fabricated using a casting process [23], PLZM Bi-2212 monoliths [24] and Bi-2212 tapes [25].…”

Visualisation of environmental degradation in ceramic superconductors using digital speckle photography

“…Like in other partial-melting processes used to fabricate Bi-2212 based tapes, 6 this laser process produces an incongruent melt and during solidification several phases appear. 7 In particular, Bi 2 Sr 2 CuO 6+δ (Bi-2201) and (Sr,Ca)CuO 2 are the main phases in the as-grown sample. After an adequate annealing, the Bi-2212 phase is recovered.…”

“…After an adequate annealing, the Bi-2212 phase is recovered. 7,8 As a consequence of the phase segregation induced by the melting texturing technique the annealed samples shows a layer close to the surface where the amount of (Sr,Ca)CuO 2 is important. 7 The stability in water environment of multi-phase Bi-2212 materials was previously studied.…”

Barras texturadas de (Bi_1.6Pb_0.4)Sr₂CaCu₂O_8+δ dopadas con Ag

“…The material presents an incongruent melting and, in consequence, after texturing, it is necessary to perform a thermal treatment in order to form the Bi-2212 superconducting phase (14). This annealing process is performed under air, and consisted in two steep: 60 h at 845ºC followed by 12 h at 800ºC and, finally, quenched in air to room temperature.…”