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Title of Thesis

Preparation and Characterization of Bi-based high-Tc superconductors

Author(s)

Khawaja Zakaullah

Institute/University/Department Details
Ghulam Ishaq Khan Institute of Engineering Sciences & Technology, Swabi
Session
2010
Subject
Engineering Sciences
Number of Pages
108
Keywords (Extracted from title, table of contents and abstract of thesis)
Highest, Porosity, Preparation, Thermo, Reaction, Method, Characterization, Parameters, Sandwiched, Superconductors, Bibased, High, Crystallization

Abstract
BSCCO ceramic superconductors prepared by powder in tube, solid state reaction and melt quenching methods have been investigated.The aim is to determine the characteristics optimum doping concentration, quenching temperature and quenching medium for BSCCO ceramic superconductors.
Studies were carried out on three systems (System I. Bi1.7Pb0.3Sr2Ca2-xBxCu3Oy, System
II. Bi1.6Pb0.4Sr2Ca2M1Cu3Oy, System III. Bi1.6Pb0.4Sr2Ca2Cu3Oy. In system I Ag- sheathed BSCCO tapes were prepared by PIT (powder in tube) technique. Samples were prepared by conventional solid state reaction followed by sintering at 850oC. In system II, Melt quenching method was adopted to prepare BSCCO samples doped with Samarium and Terbium (M=Sm,Tb). In system III, BSCCO samples were prepared by melt quenching method. The synthesized precursors were quenched from 1200oC, 1250oC and 1300oC to room temperature and sandwiched between brass, stainless steel,copper and bronze blocks.Critical temperatures of the samples were determined by resistivity temperature measurements using four probe technique at liquid nitrogen temperatures. Tc values for the samples were in the range (Tconset ~ 99K – 104K). XRD analyses were done and lattice parameters of the samples were determined by indexing the diffraction peaks.Porosity of the samples was also measured. Surface of the samples was studied by scanning electron microscope (SEM) micrographs at a magnification of X1000.The SEM results indicate that 2223 phase may have been formed and the long grains of this phase might be obtained by quenching at this temperature. The atomic distribution ratio of each component element on the surface of the sample was investigated by energy dispersive spectroscopy (EDS).Bulk density of the samples was calculated by liquid immersio method.Density was found to be > 90% of the theoretical density of BSCCO glasses.The samples were thermo analytically analyzed by differential thermal analyses (DTA) and thermogravimetric Analysis (TGA). Activation energy, reaction rate constant and frequency factor for crystallization were evaluated employing different models.
The sample quenched from 1250oC on brass had the highest value of Tc (onset), highest volume fraction of 2223 phase, highest value of density and narrowest transition width.Multiphase structure of the samples was observed, major high-Tc 2223 phase coexists with small percentage of 2212 phase. Kinetic studies revealed that the thermal stability (ΔT = Tx – Tg) increases for the sample quenched from 1250oC. According to the results obtained it may be said that the structural, superconducting and thermoanalytical properties were optimum for the sample quenched on brass from 1250oC.

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS

 

 
54 KB
2

1

LITERATURE REVIEW

1.1 Introduction
1.2 Superconductors
1.3 Types of superconductors
1.4 Superconducting Materials
1.5 Chronological developments
1.6 Superconducting theories  LTS theories
1.7 Desired properties of HTS
1.8 Cuprate superconductors
1.9 BSCCO
1.10 Applications of BSCCO superconductors

1
504 KB
3 2 EXPERIMENTAL METHODS AND CHARACTERIZATION TECHNIQUESE

2.1 Sample Preparation
2.2 Processing techniques
2.3 Sample Characterization
2.4 Dc electrical resistivity
2.5 X-ray diffraction
2.6 Scanning electron microscopy
2.7 Energy dispersive spectroscopy
2.8 Thermo analytical characterization

33
343 KB
4 3 BORON DOPED AG – SHEATHED BSCCO TAPES

3.1 XRD analysis
3.2 Dc electrical resistivity
3.3 Thermo analytical analysis
3.4 Summary

47
 212 KB
5 4 MELT QUENCHED BSCCO GLASSES

4.1 XRD analysis
4.2 Dc electrical resistivity
4.3 Microstructural analysis by SEM
4.4 EDS analysis
4.5 Density measurement
4.6 Porosity measurement
4.7 Thermoanalytical analysis
4.8 Summary

56
580 KB
6 5 DOPING IN BSCCO

5.1 XRD analysis
5.2 Dc electrical resistivity
5.3 Thermoanalytical analysis
5.4 Summary

75
268 KB
7 6 REFERENCES

87
130 KB