Improvement of structural and superconducting properties of Bi-2212 textured rods by substituting sodium

Abstract

In this study, the physical and superconducting properties of Bi 2 Sr 2 Ca 1-x Na x Cu 2 O 8+ (x=0.0, 0.05, 0.075 0.1, and 0.20) textured superconducting rods prepared by a laser floating zone technique were presented. The effect of Na +1 substitution for Ca 2+ has been investigated by Xray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transport measurements, dc-magnetization, magnetic hysteresis and magnetic critical current density. The powder XRD patterns of samples have shown that Bi-2212 phase is the major one, independently of Na content. Transport measurements indicate that, in general, the transport critical current density of samples is increased by Na substitution compared with the pure sample. In all cases, a good orientation of grains with the growth axis was observed in microstructural studies. The best critical temperature, T C , was found as 93.3 K for the sample with 0.75Na substitution, under a DC magnetic field of 50 Oe in ZFC mode. It was also observed that the magnetic critical current density obtained from magnetic hysteresis curves by using the critical Bean's model, increases with increasing Na-substitution. The maximum magnetic J C value was determined as 1.35x10 5 A/cm 2 at 10 K for the 0.10Na sample. The maximum transport critical current density was directly measured as 1.3x10 3 A/cm 2 at 77 K for the 0.05Na sample.

Effect of Na substitution on superconducting properties of Bi-2212 ceramics prepared by Sinter-Forged process

“…Moreover, they clearly show a marked preferential orientation already described in the XRD data [35,36]. The effect of Na doping can be seen in the larger grain sizes of these samples, compared with the undoped ones, in a clear agreement with previously published data [28,29,37]. Especially, 0.05, 0.075, and 0.1 Na substituted samples possess larger angles between adjacent grains which imply better intergranular characteristics.…”

“…In previous works, Bi2Sr2Ca1-xNaxCu2O8+bulk and textured ceramics with different Na content, prepared by a polymer solution method and the LFZ technique, respectively [28,29], have been studied. The effect of Na on the microstructural features, critical temperature TC, magnetic properties and magnetic JC have been determined.…”

“…If the temperature is too low to form a minimal liquid phase, the process does not offer the necessary conditions to produce high densification and grain orientation. On the other hand if the temperature is too high, a melt will be obtained, leading to glassy materials by quenching [21].In previous works, Bi2Sr2Ca1-xNaxCu2O8+bulk and textured ceramics with different Na content, prepared by a polymer solution method and the LFZ technique, respectively [28,29], have been studied. The effect of Na on the microstructural features, critical temperature TC, magnetic properties and magnetic JC have been determined.…”

Effect of Na-substitution on magnetoresistance and flux pinning energy of Bi-2212 ceramics prepared via hot-forging process

“…In previous studies, it has been reported that when the samples are produced by partial or total melting, Na substitution for Ca in Bi-2212 system provides high Tc values [18,39,40]. In addition, the polymer solution technique involving polyethyleneimine (PEI) is also useful to enhance the critical temperature, Tc, in the Bi-2212 phase [41].…”

“…In addition, the polymer solution technique involving polyethyleneimine (PEI) is also useful to enhance the critical temperature, Tc, in the Bi-2212 phase [41]. Moreover, Bi-2212 bulk sintered, textured and sintered-forged ceramics with different Na content, produced via PEI, Laser Floating Zone (LFZ) and sintered-forging techniques, respectively, were worked out [13,18]. In the framework of this study, we intend to investigate the magnetoresistive properties of the Bi 2 Sr 2 Ca 1-x Na x Cu 2 Ox with x=0.0, 0.05, 0.075, 0.10, and 0.15 textured materials produced via the hot-forging method.…”