Effect of Postannealing Process on Bi2Sr2.1Ca0.9Cu2O8+δ Textured Superconductors

Abstract

Bi-2212 samples prepared by the classical solid-state method have been grown from the melt using the Laser Floating Zone (LFZ) method. They have shown good grain alignment and transport critical current densities (J c). After postannealing processes designed to produce the Bi-2212 phase controlled decomposition, J c values have been increased in an important manner. Maximum values have been achieved when samples were thermally treated at 680 ºC for 168 h with improvements around 80 %, compared with the original textured samples. The results clearly indicate that postannealing processes, when adequately controlled, produce the formation of effective pinning centers which are responsible for the raise in the measured J c values.

Effect of Secondary Annealing Process on Critical Current Density in Highly Textured Bi-2212 Superconducting System

“…All these results agree with the previously ones obtained in similar works. 31,34 When the samples are thermally treated at 900°C, the phase decomposition is much quicker due to the formation of a liquid phase, in agreement with the phase equilibrium diagram. 31 In this case, the Bi-2212 phase is still the major one (#1, grey contrast).…”

“…These phases are in accordance with the expected ones from the previously mentioned phase equilibrium diagram 31 and with those observed in previous works in this system. 34 Electrical resistivity variation with temperature for the annealed and secondarily annealed samples is presented in Fig. 3.…”

“…[27][28][29][30] The second one is the formation of effective pinning centers by a temperature-controlled decomposition of the superconducting phase, producing insulating phases with sizes dependent on the thermal treatment duration. [31][32][33][34] The aim of this work is to develop a simple process to produce effective pinning centers by the controlled decomposition of the superconducting Bi 2 Sr 2 CaCu 2 O 8+d (Bi-2212) phase by secondary annealing treatments using different temperatures and durations. The optimal processes should raise the transport and magnetic J c of LFZ-grown Bi-2212 superconducting samples without a drastic microstructural modification.…”