After nearly seven years of research effort since the discovery of iron-based superconductors, wires and tapes of K-doped BaFe2As2 have finally been developed by the inexpensive and scalable powder-in-tube technique with critical current densities reaching over 0.1 MAcm-2 at 4.2 K. Such progress relies heavily on the development of synthesis techniques that eliminate cracks and secondary phases. High energy ball milling, during which mechanochemical reactions take place, proves to be effective in producing high quality bulk material. The consolidation of high quality powders under high pressure produces bulk material with a fine grain microstructure and surprising high intergranular current density. We explore the dependence of doped Ba2Fe2As2 superconducting properties on sintering temperature in bulks, wires, and tapes to further optimize these materials and find that grain boundaries continue to act as weak-links, effectively blocking current, and limiting the intergranular critical current density in these materials. However, evidence for composition variation and impurity segregation across grain-boundaries suggests that the weak-linked behavior may still be of an extrinsic nature. Despite the current limiting effects of these weak-links, transport current is high enough in our fine grain material to demonstrate the first > 1 T magnet made out of an iron-based superconductor. These results provide a positive outlook for the potential future use of these materials to produce high field magnets. / A Dissertation submitted to the Department of Materials Science and Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2015. / April 9, 2015. / Ba122, ferropnictide, mechanochemical, superconductivity, superconductor / Includes bibliographical references. / Eric Hellstrom, Professor Directing Dissertation; Gregory Boebinger, University Representative; David Larbalestier, Committee Member; Theo Siegrist, Committee Member; Per Arne Rikvold, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_253060 |
| Contributors | Weiss, Jeremy (authoraut), Hellstrom, Eric (professor directing dissertation), Boebinger, Gregory S. (Gregory Scott) (university representative), Larbalestier, D. (David) (committee member), Siegrist, Theo M. (committee member), Rikvold, Per Arne (committee member), Florida State University (degree granting institution), Graduate School (degree granting college), Program in Materials Science (degree granting department) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (147 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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