published_or_final_version / Physics / Doctoral / Doctor of Philosophy

No description available.

No description available.

Thesis (Ph. D.)--California Institute of Technology, 1992. UM #92-32, 184. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/01/2010. Includes bibliographical references.

Apparatus to measure the thermal conductivity of YBa(_2)Cu(_3)O(_7-δ) at temperatures between 20K and 120K has been designed and constructed. The thermal conductivity is measured using a longitudinal steady state heat flow technique. Thermal conductivity measurements have been performed upon a sample of YBa(_2)Cu(_3)O(_7-δ) which has been subjected to a series of heat treatments in order to remove oxygen from the material. The measurements show conclusively that the thermal conductivity of YBa(_2)Cu(_3)O(_7-δ) is very strongly influenced by the oxygen content of the material. A reduction of the oxygen content of the material results in a substantial lowering of the thermal conductivity. To explain this result, a quantitative model has been constructed; the model demonstrates that consideration of the changes in phonon interactions alone cannot account for the differences in the behaviour of the thermal conductivity of YBa(_2)Cu(_3)O(_6) and YBa(_2)Cu(_3)O(_7). In addition; the model, shows that there must be a significant carrier contribution to the thermal conductivity in both the normal and superconducting states. A physical process has been proposed which provides the required large carrier contribution below T(_c). Further studies have been performed on a series of samples of YBa(_2)Cu(_3)O(_7-δ) which were sintered at slightly different temperatures. Qualitative analysis of the physical properties, of these samples has been performed.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references.

Methods of processing large grained textured superconductor have been successfully developed, based on a melt texturing process. Large grained textured superconductor with grain size over 10mm along the growth direction and Jc over 3600A/cm² (77K, 0.5 Tesla) has been produced in both one - zone and two - zone furnaces with good reproducibility. Two kinds of design of reactive metal contacts have been proposed and investigated, aiming to make low resistivity contacts with strong mechanical strength. Three possible reactive contact metals have been tested for contact making, and the microstructures at the interfaces have been studied to find the relations between contact resistivity and contact processing conditions. Titanium/noble metal multilayer contacts is a promising type of contact technique for low resistivity and strong mechanical bonds. Gold and silver contacts give resistivities among the best reported results in the literature, and they turned out to be extremely stable in time, could withstand repeated thermal cycling from room temperature to 10K and yield very reproducible R-T curves. The electrochemical titration method has been used to increase the oxygen stoichiometry of bulk textured YBa₂Cu₃O_7-x samples. The electrochemical titration method can further oxidize melt textured thick film YBa₂Cu₃O_7-x samples in which it may be difficult to further improve oxygen content by conventional annealing. The solid state electrochemical cell has been used to study the thermodynamic properties of the Y-Ba-Cu-O system at high oxygen pressure by measuring the oxygen activity versus time continuously immediately after the electrochemical titration. A series of computer models have been set up according to the microstructure of the contact interface to simulate the complicated contact resistivity behaviours. The nature of, and geometry of, the reaction products at the contact interfaces may be revealed by the temperature dependence of the contact resistance. This information combined with direct observations on the structure and chemistry of the contacts provided a fuller understanding of conduction mechanism at the contact interface.

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves l05-110). Also available via World Wide Web.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2006 / Keywords: Superconductivity, bolometer. Includes bibliographical references (leaves. 74-78).