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Effects of Boron Dropping on Superconductors

#G-1362


Effects of Boron Doping on Superconducting Properties of Pb-Free and Pb-Substituted Bi-2212 and Bi-2223 Phases

Tech Area / Field

  • MAT-CER/Ceramics/Materials
  • MAT-SYN/Materials Synthesis and Processing/Materials
  • PHY-SSP/Solid State Physics/Physics

Статус
3 Approved without Funding

Дата регистрации
11.11.2005

Ведущий институт
Institute of Cybernetics, Georgia, Tbilisi

Соавторы

  • Nagoya University / EcoTopia Science Institute / Division of Energy Science, Japan, Nagoya\nUniversity of Waterloo, Canada, ON, Waterloo\nTokyo University of Marine Science and Technology / Superconductivity Research Laboratory, Japan, Tokyo

Краткое описание проекта

The objective of the project is to investigate the effects of boron-doping on the formation kinetics, electrical, magnetic and structural properties of Pb-free and Pb-substituted Bi-2212 and Bi-2223 ceramic and glass-ceramic high-temperature superconductors (HTSC), prepared via methods of the solid–state reaction and crystallization from amorphous matrix.

Actuality of the project is caused by the fact, that establishment of an easier synthesis conditions of HTSC materials and search for effective ways to improve their superconducting characteristics has been one of the interesting challenges of high-Tc superconductivity both for understanding the superconducting mechanism as well as for practical applications.

Since the discovery of Bi2Sr2Ca1Cu2Oy (Bi-2212, Tc=80K) and Bi2Sr2Ca2Cu3Oy (Bi-2223, Tc=105K) superconductors, a great number of studies have been reported on the effects of substitution and addition of various elements in the Bi-2212 and Bi-2223 superconducting phases. The majority of these studies have concluded that the crucial for practical applications characteristics of Bi-based HTSC materials (critical temperature Tc, critical current density jc and superconducting volume fraction) show a degrading tendency as the dopant concentration increases. However, introduction of proper dopants can enhance the superconducting properties of Bi-based HTSC phases. For example, partial substitution of Bi by Pb is the most widely used method to enhance the phase formation kinetics as well as to increase the superconducting volume fraction of the Bi-2223 phase. The incorporation of the Li, Pb, or Pb+Li elements into the Bi-2212 phase also exhibits the effects of raising superconducting volume fraction as well as of Tc and jc. Nevertheless, the physical properties of doped Bi-based HTSC materials are still not fully investigated and it is of great scientific and technological interest to search the effective dopant element for the enhancement of superconducting properties in the Bi-based phases besides the Pb and Li elements.

To project participants’ knowledge, influence of boron-doping on the formation, superconducting characteristics and structure of Pb-free and Pb-substituted Bi-2212 and Bi-2223 phases have not studied in detail yet. Because of the extremely small ionic radius (0.27Å), unlike the Pb and Li elements, boron will be introduced in the starting compositions of the Bi-2223 and Bi-2212 cuprates as the additive but not as the substituent for bismuth, copper or other constituents of the Bi-2212 and Bi-2223 phases. Lowering of the partial melting temperature of Bi-based HTSC phases due to the doping was found to be very important to enhance the superconducting phase formation, Tc and jc, i.e., Pb and Li elements acted as a flux. Melting temperature Tm of B2O3 is very low (Tm294oC) and boron is interesting candidate of suitable dopants to enhance the superconducting properties and superconducting phase formation kinetics in the Bi-based HTSC materials. Furthermore, B2O3 is a glass former and superconducting fibers or other forms with improved superconducting properties are obtainable in principle in the boron-doped Bi(Pb)-Sr-Ca-Cu-O system via crystallization from melt-quenched glass preforms.

The innovation of the proposed project is that comparative analysis of current-carrying, magnetic and structural properties of the series of boron-doped Pb-free and Pb-substituted Bi-2212 and Bi-2223 compounds, synthesized via methods of solid-state reaction and crystallization from amorphous matrix, will be carried out for the first time. Influence of boron-doping on the formation of Bi-2212 and Bi-2223 phases will be established. Resistivity ρ, critical current density jc, magnetic susceptibility χ and powder X-ray diffraction (XRD) studies, as well as differential thermal analysis (DTA) will be performed on ceramic and glass-ceramic samples of Bi-2212 and Bi-2223 phases. In order to obtain superconducting materials with improved current-carrying ability, the influence of additional annealing at low temperatures in the range of 300 to 600oC on the coupling nature at grain boundaries of the boron-doped Pb-free and Pb-substituted Bi-2212 and Bi-2223 phases will be investigated. The structural role of boron in the Bi-2212 and Bi-2223 phases will be clarified. Synthesized materials will be potentially suitable for fabricating high-Tc superconducting wires and glass-ceramic samples of various shapes.

The scope of activities is 2000 Person*days. Project team has been studying the superconducting properties of Y-and Bi-based HTSC for over 7 years.

Meeting ISTC goals and objectives are caused by the fact that in case the project is practically implemented, the specialists who in the past were occupied in the military fields will have the chance to implement their knowledge in scientific research for peaceful purposes.

The potential role of foreign collaborators consists in the information exchange during implementation of the project, conduction of joint seminars and examination of project activities.


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