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

Abstract

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...

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

“…Polycrystalline precursors of Bi 2 Sr 2 Ca 1-x Na x Cu 2 O x where x=0.0, 0.05, 0.075, 0.10, and 0.15 were produced by using a polymer solution method [10,20]. The details of sample preparation were given in elsewhere [20]. Powder XRD patterns of textured ceramic samples were taken by using a Rigaku D/max-B X-ray powder diffractometer (CuKα radiation) with 2θ ranging between 3 and 80 degrees.…”

“…On the other hand, for obtaining bulk high-Tc monoliths with well-oriented grains, one successfull way is using the hot-forging method [20,38]. Through this technique, it is easy to obtain a good grain orientation perpendicular to the press axis.…”

Preparation of Bi2Sr2CaCu2O8+δ(Bi2212) superconductor by Pechini sol–gel method: thermal decomposition and phase formation kinetics of the precursors

“…Bi 2 Sr 2 Ca n Cu n?1 O 8?d (Bi-based) high-temperature superconductors have been widely focused as their non-toxicity, rare-earth-free and various phase composition [1][2][3][4]. The most typical Bi-based cuprate superconductors are Bi2201 (n = 1, Michel et al 1987), Bi2212 (n = 2, von Schnering et al 1988), and Bi2223 (n = 3, Takano et al 1988), whose critical transition temperature (T c ) can arrive at 20 K, 90 K, and 110 K, respectively [5][6][7].…”

Effect of Cesium Substitution on the Superconducting Properties of Bi-2212 Samples Prepared Via Solid-State Reaction and Laser Floating Zone Technique

“…When Bi and Ca contents are reduced, provided that the oxygen content is constant, T c values are remarkably increased [3]. Since their discovery, researchers have performed many experimental efforts in order to better understand the relationship between their microstructure and physical properties, trying to improve their T c and critical current density, J C (maximum current transported by the material without passing to the normal state), for technological applications [4][5][6][7][8][9][10][11][12][13][14].…”