On residual stress measurements in yttrium-based superconductor

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" On residual stress measurements in yttrium-based superconductor "
S. N. Alfaer

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112863
Doc. No	:	TLpq304480314
Main Entry	:	S. N. Alfaer
Title & Author	:	On residual stress measurements in yttrium-based superconductor\ S. N. Alfaer
College	:	King Fahd University of Petroleum and Minerals (Saudi Arabia)
Date	:	1998
student score	:	1998
Degree	:	M.S.
Page No	:	67
Abstract	:	XRD and residual stress usd({\sim}\sin\sp2\psi)usd measurements were carried out on usd\rm YBa\sb2Cu\sb3O\sb{x}usd superconductor with varying oxygen stoichiometry usdx = 6.32usd to 7. Using published data for c-axis, T{c} and oxygen content it was found that the measured c-axis varies linearly with and is sensitive to variation of oxygen content and T{c}. Variation of a and b parameters with oxygen content revealed a transition from orthorhombic to tetragonal at 6.48. Orthorhombicity and volume of the unit cell were plotted against oxygen content and an unexpected volume contraction of the unit cell was observed. This was discussed in terms of energetically favored filling of oxygen sites. Slopes of the strain versus sin which is proportional to the residual stress, were plotted against oxygen content for certain reflections (006) and (115), for example. Different behaviors were observed and are attributed to a c-axis compressional stress increasing with oxygen content and an overall tensile residual stress in the ab-plane is also increasing oxygen content. Both effects reach saturation near fully oxygenated state usdx\ \approx\ 7.usd This explains the anomalous very small hydrostatic pressure effect on T{c} for fully oxygenated YBa2Cu3O{x} (usdx\ \approx\ 7)usd compared to a relatively high effect for oxygen deficient material. Similar results were observed for the oxygen disorder effect. Changes in T{c} for disordered material is attributed to changes in the residual stress induced by disorder phenomena.
Subject	:	Condensation
	:	Pure sciences
	:	yttrium barium copper oxide