University of Twente Student Theses


Possible strain scaling relation for YBCO superconductors?

Mulder, Tim and Ihns, Melanie (2011) Possible strain scaling relation for YBCO superconductors?

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Abstract:Superconductors have been investigated for a long time. But since the discovery of high temperature superconductors first in 1986, there has been done more research on low temperature superconductors than on HTS. So the behavior in the low temperature region of superconductors is already well known, but because industry aims to work with superconductors with increasing temperatures now high temperature superconductors have to be investigated. For high temperature superconductors there is up to now no widely accepted theory how superconductivity occurs. There is no cooling of the atoms which reduces the lattice oscillations as in the case of low temperature superconductors and so it shouldn‟t be possible for electrons to follow all the same path and so having no resistance in the superconductor. Adding strain to a superconductor causes another change in the crystal lattice. The aim of this bachelor assignment is to explore whether it is possible to find a strain scaling relation for yttrium barium copper oxide (YBCO) superconductors. When a material becomes mechanically strained, the crystal lattice becomes distorted. This influence is directly observable in the superconducting properties. These properties are best described with the so called critical surface of a superconductor. Not only the temperature is a critical parameter for superconductivity, but also the current and the applied magnetic field. This so-called critical surface will be constructed for the high temperature region of YBCO, which will be from 89K to 92K, for different magnetic fields (from 0T to 0.3T) and different values of strain. The critical current and critical temperature found for different values of magnetic field in both the compressive and tensile strain region show non-linear behavior, peaking in both the compressive and tensile strain region. These finding match the finding of other groups researching the strain behavior of YBCO. Due to this non-linear behavior of the critical current of YBCO, expressions that were used in the past as strain scaling relations for LTS (like Nb3Sn superconductors) cannot be used to scale the superconducting properties of YBCO with strain. The existing scaling relation describing the curves for YBCO does not depend on strain and so could be used to find the strain scaling relation. To make strain scaling possible for YBCO superconductors, more measurements are needed to insert the non-linear behavior of the critical current, obtained by adding strain to the sample, into the existing scaling relation.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics BSc (56962)
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