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Improvement of critical current density in YBa2Cu3O7-δ films with nano-inclusions

Awang Kechik, Mohd Mustafa (2011)
Ph.D. thesis, University of Birmingham.

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Abstract

A high critical current density Jc is crucial for the application of HTS YBa2Cu3O7-δ (YBCO) in the fabrication of energy efficient power devices and wires. We have prepared and studied YBCO films with nanoinclusions for increasing the current-carrying capability. All films were prepared by pulsed laser deposition (PLD) on single crystal SrTiO3 (STO) substrates at optimised condition parameters. We found that the substrate temperature Ts of 780° C, laser energy E ~ 218 mJ/pulses, distance between target and substrate Dt of about 55 mm, annealing oxygen pressure Oap 450 Torr and cooling rate Ct 8°/min were the optimum conditions for making good films with Tc = 91 K. We have used a method for introducing artificial pinning centers which has been shown to be successful in the nanotechnology of pinning centres: distributing a secondary phase, YBCO with 1% Gd2Ba4CuWOy (2411W) nano-inclusions, YBCO with 2% wt BaZrO3 (BZO) and YBCO with 4% wt BZO nano-crystalline particles in the film. The superconducting properties were determined by AC susceptibility, magnetisation loops and transport measurements using a Quantum Design Magnetic property measurement system (MPMS) and a Physical properties measurement system (PPMS). Scanning and transmission electron microscopy (SEM) and (TEM), Atomic force microscopy (AFM) and X-ray were also used to characterise the micro-structure of the films. Both 2411W and BZO nano-inclusions led to increased Jc in applied fields and self-field. Scaling of the flux pinning force based on the Dew-Hughes model has been used in this work for investigating the flux pinning mechanism.

Type of Work:Ph.D. thesis.
Supervisor(s):Abell, J. S. and Crisan, Adrian and Mikheenko, P
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:TN Mining engineering. Metallurgy
Institution:University of Birmingham
ID Code:2930
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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