Skip to Main Content
Frequently Asked Questions
Submit an ETD
Global Search Box
Need Help?
Keyword Search
Participating Institutions
Advanced Search
School Logo
Files
File List
ucin1075992286.pdf (15.42 MB)
ETD Abstract Container
Abstract Header
High J
c
Epitaxial YBa
2
Cu
3
O
7-δ
Films Through a Non-Fluorine Approach for Coated Conductor Applications
Author Info
Xu, Yongli
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1075992286
Abstract Details
Year and Degree
2004, PhD, University of Cincinnati, Engineering : Materials Science.
Abstract
Highly textured superconducting YBCO films are prepared through the TMAP-MOD route by coating, burnout and annealing. Films deposited either on single crystal substrates of LAO, STO and YSZ/CeO
2
, or on RABiTS with buffers of CeO
2
/YSZ/CeO
2
and Y
2
O
3
/YSZ/CeO
2
. In both cases high current density over 10
6
A/cm
2
and Tc(R=0) around 90K have been demonstrated. XRD data and TEM/SAD analysis confirmed YBCO phase epigrowth from interface. This is the first demonstration of high J
c
over 1 MA/cm
2
in a non-fluorine precursor. We found water is the key factor that helps the growth of c-axis oriented grains with a-b in plane alignment in terms of forming a liquid phase of Ba(OH)
2
. While the dendritical growth of YBCO phase in the melt results in none uniformity and a rough surface, which degrades the properties of the YBCO film. Intermediate phases associated with Y, Ba, and Cu are discussed into detail especially for the copper and barium contained phases. Mechanisms of the liquid phase (melt) formation are proposed with regarding to the function of humidity, the core-shell model has been used to explain the copper oxidation process, and the stress state of burnout films are analyzed by introducing the strain energy release rate in the Griffith model. Based on the proposed key chemical reactions, the energy process in terms of barriers and driving force is calculated. It shows that the driving force comes mainly from three factors of ΔT, P
co2
and P
o2
, and which are partially confirmed by experimental results. Consequently, an energy controlled nucleation modes have been suggested and factors of avoiding body nucleation as well as adjusting interfacial nucleation rate have been discussed. Finally, A dynamic process of rejecting impurities either to the grain boundaries or to the top surface is considered. As a result, the lateral growth mechanism has been proposed and factors based on the free energy and compositional availability that could block the dynamic growth front of YBCO phase are specified. A new growth mode by reducing driving force after nucleation is suggested, which could form small grains with less impurity segregation and weak links.
Committee
Dr. Donglu Shi (Committee Chair)
Dr. Relva Buchanan (Other)
Dr. Rodney Roseman (Other)
Dr. Amit Goyal (Other)
Pages
302 p.
Keywords
YBCO
;
HTS
;
coated conductor
;
film
;
epitaxial growth
Recommended Citations
Refworks
EndNote
RIS
Mendeley
Citations
Xu, Y. (2004).
High J
c
Epitaxial YBa
2
Cu
3
O
7-δ
Films Through a Non-Fluorine Approach for Coated Conductor Applications
[Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1075992286
APA Style (7th edition)
Xu, Yongli.
High J
c
Epitaxial YBa
2
Cu
3
O
7-δ
Films Through a Non-Fluorine Approach for Coated Conductor Applications.
2004. University of Cincinnati, Doctoral dissertation.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1075992286.
MLA Style (8th edition)
Xu, Yongli. "High J
c
Epitaxial YBa
2
Cu
3
O
7-δ
Films Through a Non-Fluorine Approach for Coated Conductor Applications." Doctoral dissertation, University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1075992286
Chicago Manual of Style (17th edition)
Abstract Footer
Document number:
ucin1075992286
Download Count:
871
Copyright Info
© 2004, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.