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.
Bi 2 Sr 2-x Na x Co 2 O y thermoelectric materials with x = 0, 0.025, 0.05, 0.075, 0.10, 0.125, and 0.15 have been prepared by solid state reaction. Microstructure has shown an important grain growth when Na is added, leading to very high bulk densities confirmed through density measurements. These modifications have produced a drastic decrease of electrical resistivity without significant modification of Seebeck coefficient. As a consequence, Power Factor has been increased in all Na-doped samples, reaching the maximum value (0.21 mW/K 2 .m at 650 ºC) for 0.075 Na samples, which is fairly close to the reported for single crystals.
AbstractsBulk textured Bi2Sr2Ca1-xNaxCu2Oy (x=0.0, 0.05, 0.075 0.1, 0.15, and 0.20) ceramics have been prepared by a polymer solution method followed by sinter-forging process. The microstructure and superconducting properties of textured samples were affected by Na substitution. According to XRD data, all samples show that Bi-2212 phase is the major one, and main peaks corresponded to the (00ℓ) diffractions confirming that the crystallographic caxis is perpendicular to the surface. SEM micrographs showed that samples are composed of well-stacked and oriented grains. The best critical temperature, TC, was measured as 85.6 K for x=0.075. The critical current density Jc, values decrease gradually with the increase of applied magnetic field. The maximum calculated Jc was 1.38x105 A/cm2 at 10 K for 0.075 Na sample which is about four times higher than the 0.34x105 A/cm2 value determined for the pure sample. The anisotropic properties of these textured materials have been investigated using magnetic measurements. KeywordsBi-2212; Sodium Substitution; Texturing; Anisotropy; Sinter-Forging Method. δ, where n=1, 2 and 3, with Tc values around 20, 90 and 110 K, respectively. These three phases are referred to as Bi-2201 (n=1), Bi-2212 (n=2) and Bi-2223 (n=3). The synthesis of pure Bi-2201 and Bi-2212 phases in this system is relatively easy, while the Bi-2223 single phase production has been shown to be a difficult task. As a consequence, the development of synthesis procedures which can lead to single phase ceramics, with a well defined Tc, has been a main objective in many works.On the other hand, when considering practical applications, the fabrication of high temperature superconductors having high electrical transport capacity at 77 K is of great interest [2]. In particular, BSCCO family has been found suitable for many transport applications when they are properly processed in order to obtain a good grain orientation [3,4]. In order to enhance the critical temperature (Tc) and transport critical current (Jc), many techniques were used leading to high performance materials, such as thin [5,6] and thick film [7] technology, wires and tapes by the PIT method [8], and texturation using the Bridgman [9], Laser Floating Zone (LFZ) method [10-16], or the newer Electrically Assisted Laser Floating Zone method [17-20].Among these techniques successfully used to produce well textured materials [21][22][23], the directional growth from the melt by the LFZ method has demonstrated to be a very useful technique for producing well textured BSCCO rods at high growth rates. As it was previously reported [13], the microstructure of the superconducting ceramics is characterized by a good grain alignment, with their c-axis quasi-perpendicular to the growth direction. This high degree of texture leads to a very important increase of the transport properties, Jc, due to the reduction of the number of low-angle junctions [24]. After the growth process, due to the incongruent melting of this phase [25], it is necessary to subject the samp...
In this study, the physical and superconducting properties of the Bi 2 Sr 2 Ca 1-x Y x Cu 2 O 8+ with 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 Y 3+ substitution for Ca 2+ has been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), dc-magnetization, magnetic hysteresis and critical current density calculation by using the Bean's critical state model. The powder XRD patterns of samples show that Bi-2212 phase is the major one. Along with the powder samples, the textured rod surfaces also were investigated by XRD. The grains found to be well-oriented along the longitudinal rod axis which is a typical result for superconductors prepared by laser floating zone (LFZ) method, has been observed. The best critical temperature, T C , has been found as 92.9 K for the sample with 0.15Y substitution, under DC magnetic field of 50 Oe in ZFC mode. It has also been observed that the critical current density decreases with increasing Ysubstitution. Using those values, the maximum J C value has been determined as 2.37x10 5 A/cm 2 for the undoped sample.
a b s t r a c tThe effects of post-annealing temperature were investigated on Bi 2 Sr 2 Ca 1 Cu 2 O 8+o thin films deposited on MgO (1 0 0) substrates by pulsed laser deposition (PLD). The structural and superconducting properties of the films have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature depende nt resistivity (R-T), and DC magnetization measure ments. The films which were deposited at 600 °C were post-annealed in an atmosphere of a gas mixture of Ar (93%) and O 2 (7%), at temperature ranging between 800 and 880 °C. This resulted in films which exhibited a single phase of 2212 with a high crystallini ty (FWHM % 0.16°) and texturing along the c-axis, perpendicular to the plane of the substrate. An optimum temperature of 860 °C was found for the post-annealing thermal treatment. The critical temperature, T C , of the films was measure d as 82 K and the critical current density, J C , was calcu lated as 3 Â 10 7 A/cm 2 for the film annealed at 860 °C.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.