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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

Understanding radiation damage mechanisms in high temperature superconductors for fusion applications
Professors Susannah Speller and Chris Grovenor

Rare-earth barium copper oxides (REBCO) are the only class of high-temperature superconducting (HTS) materials that have been developed into commercial wires with an engineering performance that is suitable for use in the high field magnet assembly in small fusion tokamaks. One of the critical aspects we must understand before deciding to deploy these materials in a fusion reactor is how they respond to ionising radiation such that they can retain adequate performance for the lifetime of the reactor when exposed to high energy neutrons and a significant flux of gamma rays.

The manufactured microstructure, local oxygen stoichiometry and the distribution of flux pinning centres play crucial roles in determining the superconducting properties, but the exact mechanisms by which radiation alters these microstructural features are unclear. Different types of radiation can cause point defects and larger damage cascades, or stimulate radiolysis effects, but the quantitative relationships between initial structure, radiation type, energy and flux, specific damage processes and the final engineering properties are unknown. An understanding of these effects is needed in order to predict how the magnet performance may change during the lifetime of a reactor.  The student will work with facilities at the Culham Center for Fusion Energy, and design experiments on the Diamond Synchrotron, to develop a mechanistic understanding of how the defect structure in REBCO is affected by radiation, and how these changes control the superconducting properties.

Also see homepages: Chris Grovenor Susannah Speller

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

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 new material to use in this application. This project will focus on the fabrication of bulk MgB2 materials using the Field Assisted Sintering Technique (FAST), which may offer significant benefits over conventional hot pressing. Working jointly in the Oxford Centre for Applied Superconductivity (www.cfas.ox.ac.uk) and the Processing of Advanced Materials group (users.ox.ac.uk/~pgrant), the student will be involved in powder processing of the precursor material, the design of processing conditions, and understanding the critical links between final microstructure and superconducting properties, with the aim of optimising the magnetic field that can be trapped in the smallest possible volume. This student will be involved with an EPSRC-funded project in collaboration with Cambridge University, RAL and industrial partners at Element Six, providing opportunities to access industrial processing facilities and to integrate their material with test devices in the Institute for Biomedical Engineering.

Also see homepages: Patrick Grant 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

Controlling interfacial properties in solid state batteries using thin film techniques
Professors Susannah Speller and Chris Grovenor

Oxford University is one of the founder members of the Faraday Institution (https://faraday.ac.uk), the UK’s new flagship programme for battery science and technology.  Rechargeable lithium-ion batteries have revolutionized the portable electronics industry because of their high energy density and efficiency, and are now widely deployed in electric vehicles. However, they suffer from significant safety and reliability issues, many of which are related to the use of flammable liquid electrolytes. There is a world-wide race to design and manufacture solid-state electrolyte materials that could resolve some of these problems. A range of oxide, phosphate and sulphide compounds have rather lower conductivities than liquid electrolytes, but show promise for use in prototype all solid-state battery designs if the thickness of the electrolyte can be reduced.  The interfaces between electrodes and electrolytes are also well known to be electrochemically unstable, and strategies to modify the interfacial properties are being explored.

This project will  use thin film deposition techniques (pulsed laser deposition and magnetron sputtering) to modify chemistry of interfaces between electrode and electrolyte materials in order to improve the cycling performance of prototype solid state battery designs.  The influence of the deposition parameters on the phase, microstructure and mechanical properties of the films will be studied using XRD and electron microscopy techniques to establish the optimised growth conditions, and the electrochemical performance of promising structures will be measured.

Also see homepages: Chris Grovenor Susannah Speller

Joints between low temperature and high temperature superconducting materials for future magnet systems
S C Speller / C R M Grovenor

The next generation of ultra-high field magnets will rely on the unique properties of high temperature superconducting (HTS) materials in the highest field regions, but will also use cheaper conventional low temperature superconducting (LTS) materials like NbTi and Nb3Sn for the lower field areas.  Magnets would be much simpler to build if superconducting joints could be made first between lengths of HTS REBCO coated conductor materials, and  also between HTS and LTS materials, but there have been no reliable processing strategies yet designed to manufacture these HTS/LTS  joints.  The student, working closely with our industrial partners Oxford Instruments and Siemens Healthineers, and with partners at CERN, will use facilities in the Centre for Applied Superconductivity (cfas.ox.ac.uk) to study the feasibility of making joints between state of the art commercial superconducting materials, to understand how to control unwanted reactions at the joint interfaces and to measure their performance. There will be opportunities for the student to spend time in the laboratories of these partners, 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

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