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Susannah Speller

Professor Susie Speller
Associate Professor of Materials

Department of Materials
University of Oxford
16 Parks Road
Oxford OX1 3PH
UK

Tel: +44 1865 273734 (Room 110.20.05)
Tel: +44 1865 273777 (reception)
Fax: +44 1865 273789 (general fax)

Centre for Applied Superconductivity

Summary of Interests

The Superconducting Materials research group focusses on relationships between processing, microstructure and properties of a wide range of superconducting materials. A major part of our current research activity is associated with the Oxford Centre for Applied Superconductivity (CfAS) and  involves working closely with local industrial partners to address materials challenges in the superconducting magnet industry, such as superconducting joints.  In addition, we specialise in the processing and characterisation of thin films, and have a new research intersest in superconducting nitride materials for quantum device applications as well as an ongoing activity supplying Tl-based high temperature superconducting films to research collaborators.  On the more fundamental side, I use advanced microstructural characterisation techniques including High-Resolution Electron Backscatter Diffraction (HR-EBSD) and synchrotron microscopy (e.g nanoARPES, PEEM) to study homogeneity and phase separation in single crystals of novel Fe-based superconductors.  Understanding the interplay between magnetism and superconductivity in these materials is thought to be of crucial importance for discovering the elusive mechanism for high-temperature superconductivity. 

Current Research Projects

Superconducting joints in technological materials
T Davies, Prof. S.C. Speller, Prof. C.R.M. Grovenor, Dr M'hamed Lakrimi*
This project aims to explore strategies for producing superconducting joints between a variety of different technologically-important superconducting wires, focussing on using novel high resolution imaging techniques to characterise the local microstructure, chemistry and superconducting properties. The project aims include developing lead-free materials for presistent mode joints in MRI magnets.  Strategies for jointing HTS materials with conventional low-temperature superconductors, such as NbTi and Nb3Sn, will also be investigated.  (*Siemens Magnet Technology).  Projects supported by Industrial Case Studentship from SMT.

Characterisation of Fe-based superconductors
Dr. S. Speller, Professor C.R.M. Grovenor
High resolution EDX and EBSD analysis techniques are being applied  to develop a better understanding of the phase separation phenomena that may control the superconducting and magnetic properties of single crystal samples of the Fe-based superconducting family.   In collaboration with E. Pomjakushina, K. Conder, Laboratory for Developments and Methods, Paul Scherrer Institut

2 public active projects

Research Publications

Goodfellow, A; Shi, Y-H; Durrell, JH; Dennis, AR; Cardwell, DA; Grovenor CRM; Speller, SC “Microstructural evolution in multiseeded YBCO bulk samples grown by the TSMG process” Superconductor Science and Technology 29, 115005 (2016)

Aksoy, C; Mousavi, T; Brittles, G; Grovenor, CRM; Speller, SC. “Lead-free solders for superconducting applications”, IEEE trans. Appl. Supercond. 26(3) 7428882 (2016)

Brittles, G; Aksoy, C; Grovenor, CRM; Bradshaw, T; Milward and Speller, SC. “Microstructural properties and magnetic testing of spot-welded joints between Nb-Ti filaments”. IEEE trans. Appl. Supercond. 26(3) 7405257 (2016)

Mousavi, T; Aksoy, C; Grovenor, CRM; Speller, SC. “Phase evolution of superconducting Sn-In-Bi solder alloys”. IEEE trans. Appl. Supercond. 26(3) 7372426 (2016)

Mousavi, T; Aksoy, C; Grovenor, CRM; Speller, SC. “Microstructure of superconducting properties of Sn-In and Sn-In-Bi alloys as Pb-free solders”. Supercond. Sci. Technol. 29 015012 (2016)

Speller, SC; Mousavi, T; Dudin, P. “Analytical microscopy of iron-based superconducting materials”, Novel Superconducting Materials, 1:29-36 (2015)

Brittles, GD; Mousavi, T; Grovenor, CRM; Aksoy, C; Speller, SC. “Persistent current joints between technological superconductors”, Superconduct. Sci. Technol. 28(9) 093001 (2015).

Mousavi, T; Grovenor, C; Speller, S. “Characterization of superconducting Fey(Se1-xTex) thin films deposited on MgO substrates by sputtering”, J. Mater. Sci. 50-6970-6978 (2015)

Grant, PS; Castles, F; Lei, Q; Wang, Y: Janurudin, JM; Isakov, D; Speller, S; Dancer, C; Grovenor, CRM. “Manufacture of electrical and magnetic graded and anisotropic materials for novel manipulations of microwaves”, Phil. Trans. A 373: 20140353

Mousavi, T; Grovenor, CRM; Speller, SC, “Effects of processing conditions on the properties of Fe(Se,Te) thin films grown by sputtering”, IEEE Trans. Appl. Supercond. 25(3) 7500604 (2015)

Collins-McIntyre, LJ; Wang, W; Zhou, B; Speller, SC; Chen, YL; Hesjedal, T; DOI:10.1002/pssb.201552003 (2015)

Brittles, GD; Grovenor, CRM; Noonan, P; Keys, S; Speller, SC. “Rapid characterisation of persistent current joints by SQUID magnetometry”, Superconductor Science and Technology, 27(12) 122002 (2014)

Mousavi, T; Grovenor, CRM; Speller, SC, “Structural parameters affecting superconductivity in iron chalcogenides: review” Materials Science and Technology 30(15) 1929 (2014)

Speller, SC; Dudin, P; Fitzgerald, S; Hughes, GM; Kruska, K; Britton, TB; Krzton-Maziopa, A; Pomjakushina, E; Conder, K; Barinov, A; Grovenor, CRM, “High resolution characterisation of microstructural evolution in RbxFe2-ySe2 crystals on annealing” PRB 90 024520 (2014)

Fan Y; He, K; Tan, H; Speller, SC; Warner, JH, “Crack-free synthesis and transfer of continuous monolayer graphene grown on melted copper” Chemistry of Materials 26(17) 4984 (2014)

Zhai, W; Shi, YH; Durell, JH; Dennis, AR; Rutter, NA; Troughton, SC; Speller, SC; Cardwell, DA, “The processing and properties of single-grain Y-Ba-Cu-O fabricated from graded precursor powder”, Supercond. Sci. Technol., 26, 125021 (2013)

Watson, MD; Collins-McIntyre, LJ; Shelford, LR; Coldea, AI; Prabhakaran, D; Speller, SC; Mousavi, T; Grovenor, CRM; Salman, Z; Giblin, SR; Van der Laan, G; Hesjedal, T, “Study of the structural, electric and magnetic properties of Mn-doped Bi2Te3 single crystals”, New Journal of Physics 15, 103016 (2013)

Speller, SC; Britton, TB; Hughes, G; Krzton-Maziopa, A; Pomjakushina,E; Conder, K; Boothroyd, AT; Grovenor, CRM, Microstructural analysis of phase separation in iron chalcogenide superconductors, Supercond. Sci. Technol., 25, 084023, (2012)

Wu, YA; Fan, Y; Speller, S; Creeth, GL, Sadowski, JT; He, K; Robertson, AW; Allen, CS; Warner, JH. Large single crystals of graphene on melted copper using chemical vapour deposition, ACS Nano, May 22, 2012, DOI: 10.1021/nn3016629

Karney, GB; Buder, PG; Speller, S; Scarse JD; Richardson, CA; Shroder, M; Hughes, GH; Czernuszka, JT; Grovenor, CRM. Characterizing the microstructure of Arctica islandica shells using NanoSIMS and EBSD, Geochem, Geophys. Geosys. 13 Q04002, doi:10.1029/2011GC003961 (2012)

Wu, YA; Robertson, AW; Schäffel, F; Speller, SC; Warner, JH, Aligned rectangular few layer graphene domains on copper surfaces, CHEMISTRY OF MATERIALS, 23 (20), pp 4543–4547 (2011).

Speller, SC; Britton, TB; Hughes, G; Lozano-Perez, S; Boothroyd,AT; Pomjakushina,E; Conder, K; Grovenor, CRM, Analysis of local chemical and structural inhomogeneities in FeySe1-xTex single crystals, Appl. Phys. Lett., 99, 192504 (2011).

Speller, SC; Aksoy, C; Saydam, M; Taylor, H; Burnell, G; Boothroyd, AT; Grovenor, CRM, Superconducting FeySe1-xTex thin films grown by RF sputtering, Supercond. Sci. Technol., 24 (7), 075023 (2011)

Weigand, M; Speller, SC; Hughes, GM; Rutter, NA; Lozano-Perez, S; Grovenor, CRM; Durrell, JH, Individual grain boundary properties and overall performance of metal-organic deposition coated conductors, Phys. Rev. B, 81 (17): Art No. 174537 (2010)

Projects Available

Bulk superconducting MgB2 magnets for biomedical applications
S C Speller / C R M Grovenor

Magnetic Resonance Imaging (MRI) is a very widely used technique for medical diagnosis, but the current instruments based on superconducting solenoids are large and expensive.  There are emerging designs for much smaller and cheaper instruments for knees, elbows, wrists etc based on bulk superconductors acting as permanent magnets.  Permanent magnets also have potential applications in novel drug delivery systems. Magnesium diboride (MgB2) is a possible material to use in this application, and this project will focus on the fabrication of bulk MgB2 materials in collaboration with our industrial partners Element Six.  Working in the new Centre for Applied Superconductivity (www.cfas.ox.ac.uk) the student will be involved in powder processing of the precursor material, the design of processing conditions (T and P), and the correlation of the resulting microstructure with superconducting properties, with the aim of optimising the field that can be trapped in the smallest possible volume. There will be opportunities to integrate your material with test devices in the Institute for Biomedical Engineering.

Also see homepages: Chris Grovenor Susannah Speller

Ultra low resistance joints for high temperature superconducting magnets
S C Speller / C R M Grovenor

The next generation of ultra high field magnets are starting to require the use of high temperature superconducting materials. These magnets will require several kinds of very low resistance (persistent) joints between superconducting wires that can operate reliably in high magnetic fields. So far few potential solutions to overcoming the serious materials challenges in manufacturing these joints have been reported.  The student, working closely with our industrial partners Oxford Instruments, will use new facilities in the Centre for Applied Superconductivity (cfas.ox.ac.uk) to design novel processes to form joints between commercial wires, and measure their performance.  The initial focus of the work will be on the state-of-the-art multifilamentary wires from Oxford Superconducting Technology. There will be opportunities for the student to spend time in the laboratories of Oxford Instruments, and to become an expert in the correlation of microstructure with superconducting properties of materials critical for future magnet designs.

Also see homepages: Chris Grovenor Susannah Speller

Radiation damage in superconducting materials for Fusion applications
S C Speller / C R M Grovenor

Future designs of Fusion power machines will require superconducting magnet winding, and these superconductors will in service be subjected to high fluxes of energetic particles.  However, little is known about the effect of the lattice damage resulting from these interactions on the superconducting properties, especially in 2nd generation high temperature superconducting tapes. This studentship is a collaboration with a local company, Tokamak Energy. The project will use advanced electron microscopy techniques to identify the key damage mechanisms in a range of different superconducting materials  exposed to high energy particles, and to correlate these with direct superconducting property measurements.  This project is offered by the University of Oxford as part of the Fusion CDT programme.  Please contact Professor Chris Grovenor for more information. 

Also see homepages: Chris Grovenor Susannah Speller

A new way to manufacture high performance NbTi superconducting wires
C R M Grovenor / S C Speller

The workhorse material for high field superconducting magnets has for many years been a 2 phase NiTi alloy processed by a long and complex thermomechanical process to give a microstructure optimised to give strong flux pinning. The use of artificial pinning centres to achieve even better superconducting performance has been explored in industry, but rejected because it is too expensive. Working in the new Centre for Applied Superconductivity (www.cfas.ox.ac.uk), this project will explore an alternative route to give a microstructure that gives strong flux pinning in a simple two-stage process. The student will be involved in the metallurgical processing, microstructural assessment and superconducting property measurements on the new alloys, with advice and close interaction from our industrial partners.

Also see homepages: Chris Grovenor Susannah Speller

Also see a full listing of New projects available within the Department of Materials.