Professor Derek C Sinclair

BSc PhD CChem MRSC
Professor in Materials Chemistry

Address:
Department of Materials Science and Engineering
Sir Robert Hadfield Building
Mappin Street, Sheffield, S1 3JD

Telephone: +44 (0) 114 222 5974
Fax: +44 (0) 114 222 5943

Email: d.c.sinclair@sheffield.ac.uk

Joined the Department in 1999 from the University of Aberdeen where he was a lecturer in the Chemistry Department from 1994-9. Previously, he was a lecturer at the University of Leeds (School of Materials), 1993-4 and a Research Fellow at the Interdisciplinary Research Centre in Superconductivity, Cambridge, 1992-3.

Research interests

Our research is involved with the synthesis and characterisation of oxide-based electroceramics. The properties and applications of many electroceramics depend on the close control of the crystal structure, composition, ceramic microstructure, dopants and dopant (or defect) distribution. Materials of well-defined composition are synthesised and characterised by a variety of diffraction, spectroscopic, microscopic, analytical and thermal techniques. The electrical properties are usually characterised by ac impedance spectroscopy, in preference to dc or conventional fixed-frequency measurements. This multi-technique approach has helped rationalise the composition-structure-property relationships in important electroceramics which include ferroelectrics, solid electrolytes and high temperature superconductors.

In addition to systematic doping studies on established materials, we undertake explorative phase diagram studies and speculative synthetic work on `new´ materials with potentially useful electrical properties. This approach is being used to discover new mixed ionic/electronic conductors, proton conductors, oxide-ion conductors, piezo-, pyro- and ferro-electrics and (high permittivity) microwave dielectrics. Several of these projects are in collaboration with other staff members, including Tony West, Ian Reaney, Neil Hyatt and John Harding.

Impedance spectroscopy is a powerful technique which is being developed to probe electrical imhomogeneities in ceramics, and in particular to study electrode/sample interfaces, surface layers, electro-active grain boundaries, core-shell phenomena within electrically heterogeneous grains, ferroelectricity and ionic conduction. Much of this work has been assisted by advanced data handling techniques, such as combined impedance and modulus spectroscopy, which has been developed in collaboration with Professor Tony West. A variety of electro-materials, commercial devices and porous materials have been characterised successfully including; solid state lithium batteries, positive temperature coefficent of resistance (ptcr)-BaTiO₃ ceramics, single crystals of ferroelectric LiTaO₃, numerous solid electrolytes, Bi₄V₂O₁₁ and La_9.33(SiO₄)₆O₂, ferro-electric and Pb-free relaxors, Multi-Layer Capacitors (with AVX Ltd, Coleraine), Internal Barrier Layer Capacitors (CaCu₃Ti₄O₁₂) and pore reduced cement.

Key projects

• Ferroelectric BaTiO₃-based ceramics for multilayer capacitors.
• High permittivity oxide-based dielectrics for telecommunication applications, eg microwave resonators and filters.
• Development of non-ohmic devices, eg ptcr-thermistors and Barrier Layer Capacitors.
• Low Temperature Co-fired Ceramics (LTCC).
• Pb-free piezoelectrics and recoverable electro-strain materials for actuators.
• Bi- and Apatite-based oxide-ion conductors as solid electrolytes for sensors and solid oxide fuel cells.
• Development of Impedance Spectroscopy to characterise electroceramics.
• Muti-ferroics.

Professional activities and recognition

• Member of the EPSRC Peer Review College (Functional Materials).
• Member of the IOM3 Materials Chemistry Committee.
• Member of the IOM3 Structure of Materials Committee.
• Editorial Board Member for the Journal of the Ceramic Society of Japan.

Key publications

• D.C.Sinclair, T.B. Adams, F.D. Morrison and A.R West, 'CaCu₃Ti₄O₁₂: A One-step Internal Barrier Layer Capacitor', Applied Physics Letters, 80 (2002) 2153-2155.
• E.J. Abram, D.C. Sinclair and A.R. West, 'A Strategy for Multi-formalism Analysis of Impedance Spectroscopy Data of Electroceramics', Journal of Electroceramics, 10 (2003) 165-178.
• G.M. Keith, C.A. Kirk, V. Sarma, N Mc. Alford, E.J. Cussen, M.J. Rosseinsky and D.C. Sinclair, 'Synthesis, Crystal Structure and Electrical Characterisation of Ba(Mn_1/2Ti_1/2)O₃: a high permittivity 12R-type Hexagonal Perovskite', Chemistry of Materials, 16 [10] (2004) 2007-2015.
• A. Feteira, D.C. Sinclair, I.M. Reaney and M.T. Lanagan, 'Structure-property Relationships of Ba(Ti_1-2yGa_yNb_y)O₃ (0≤y≤0.35) Ceramics', Journal of American Ceramic Society, 88 [11] (2005) 3055-3062.
• T.B. Adams, D.C. Sinclair and A.R. West, 'Characterisation of grain boundary Impedances in fine and coarse grained CaCu₃Ti₄O₁₂ ceramics', Physical Review B, 73 (2006) 094124 -1 to9.
• L. Zhang, O.P. Thakur, A. Feteira, G. M. Keith, A.G. Mould, D. C. Sinclair and A.R. West, 'Comment on the use of Calcium as a dopant in X8R BaTiO₃-based ceramics', Applied Physics Letters, 90 (2007) 142914-1 to 3.

Research group

Antonio Feteira (Visiting Lecturer)
Rainer Schmidt (PDRA)
Peeyusha Soobagrah (PhD student)
I Sterianou (PhD student, joint with Prof Ian Reaney)
Ming Li (PhD student)
Ben Lui Bin (PhD student)
Andrew Donovan (PhD student)
Matthew Ferrarelli (PhD student joint with Professor West)
Chaou Tan (PhD student joint with Professor Reaney)
Winson Tsai (PhD student)
Andrew McQeen (PhD student)
Andrew Mould (CCL technician)

Research centres

Ceramics and Composites Laboratory