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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 / 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

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

Sputtered thin film electrolytes for new battery designs
Supervisors: Professors Susannah Speller and Chris Grovenor

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.  Candidate Li+ ion conducting garnets like Li7La3Zr2O12 and a range of phosphate and sulphide compounds have 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.  However, a reliable growth process will have to be designed to give the necessary uniformity and electrochemical performance in thin films of these complex and hghly reactive materials.

This project will explore the deposition of Li-conducting thin films by both pulsed laser deposition and magnetron sputtering.  The influence of the deposition parameters on the phase, microstructure and mechanical properties of the films will be studied using XRD, electron microscopy and nano-indentation techniques to establish the optimised growth conditions and to compare the potential of the two deposition processes as a manufacturing technique.  The electrochemical performance of promising films will be measured in collaboration with the Pasta battery group in the department.  This project will be part of Oxford’s contribution to the UK Faraday Institution, and will give the student the opportunity to be part of this new national battery institute.

Also see homepages: Chris Grovenor Susannah Speller

Nitride superconducting films for quantum device applications
S C Speller / C R M Grovenor

Many of the most exciting advances in quantum technologies rely on very high quality resonant circuits fabricated in superconducting materials. Impressive results have been achieved with nitride films as the superconducting material because they offer great stability to atmospheric attack and oxidation and low losses. Previous work on TiN films has shown that the stoichiometry uniformity, oxygen content, resistivity, texture and residual strain all have a significant impact on resonance performance, and that film uniformity over large areas will be an important issue in future complex circuit designs. Although high quality VN and MoN thin films with excellent superconducting properties can be deposited, these materials have not been much tested for use in resonant circuits. The objective of this project is to explore a wider range of new superconducting compounds and alloys, (Nb,Mo,Ti,Re)N, for low loss resonant structures. The student will use thin film growth and characterisation facilities in the Centre for Applied Superconductivity (www.cfas.ox.ac.uk) to deposit and measure the properties of nitride thin films, including correlating magnetic force microscopy and SEM observations to understand flux pinning at microstructural features, and to test the resonator performance with the quantum technology groups in Physics and Materials Departments.

Also see homepages: Chris Grovenor Susannah Speller

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