Professor Derek Sinclair

PhD, BSc, MRSRC

Department of Materials Science and Engineering

Professor in Materials Chemistry

Professor Derek Sinclair
d.c.sinclair@sheffield.ac.uk
+44 114 222 5974

Full contact details

Professor Derek Sinclair
Department of Materials Science and Engineering
Sir Robert Hadfield Building
Mappin Street
Sheffield
S1 3JD
Profile

Derek was appointed to the academic staff at the University of Sheffield in 1999 as a Lecturer in Functional Materials, following from Lecturer appointments in the Department of Chemistry, University of Aberdeen (1994-99) and the Department of Materials Science, University of Leeds (1993-94).

He obtained his BSc (1st Class Honours) and PhD (supervised by Professor Tony West) in Chemistry at the University of Aberdeen and held post-doctoral research appointments at the University of Aberdeen (with Profs Tony West and John Irvine) and the Interdisciplinary Research Centre for Superconductivity at the University of Cambridge (with Prof Paul Attfield), before joining the academic staff at Leeds in 1993.

Derek is recognised for his ability to probe the structure (crystal and defect)-composition-microstructure-property relationships of a wide range of functional oxides, spanning from superconductors to dielectrics via mixed conductors and solid electrolytes.

Research interests

Our research is involved with the synthesis and characterisation of oxide-based functional ceramics. The properties and applications of many functional ceramics 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 is backed up with atomistic modelling (defect chemistry) and finite element modelling (electrical microstructure) to rationalise the composition-structure-property relationships in important functional ceramics which include dielectrics, solid electrolytes, mixed conductors and thermoelectrics.

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, (high permittivity) microwave dielectrics and thermoelectrics. Several of these projects are in collaboration with other MS&E staff members, including Tony West, Ian Reaney, John Harding, Colin Freeman and Julian Dean. We also collaborate with Rachael Elder and Ray Allen from Chemical & Biological Engineering on solid oxide electrolysis cells as part of an EPSRC Programme Grant on Carbon Capture and Utilisation (4CU).

Impedance spectroscopy is a powerful technique which is being developed to probe electrical inhomogeneities 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 Tony West. Recently we have developed a finite element code to simulate impedance spectroscopy data (with Julian Dean and John Harding) for three-dimensional ceramic microstructures which allows comprehensive treatment of a full three-dimensional granular representation of ceramic microstructure without the requirement for equivalent circuits based on the Brickwork layer model or the introduction of constant phase elements to describe any nonideality of the impedance response. A variety of electro-materials, commercial devices and porous materials have been characterised successfully including; solid state lithium batteries, positive temperature coefficient of resistance (ptcr)-BaTiO3 ceramics, single crystals of ferroelectric LiTaO3, numerous solid electrolytes, Bi4V2O11, La9.33(SiO4)6O2 and (Na,Bi)(Ti, Mg)O3, ferro-electric and Pb-free relaxors, BaTiO3-based 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 oxides for telecommunication applications, eg microwave dielectrics.
  • 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.
  • Solid electrolytes and mixed conductors for sensors and solid oxide fuel/electrolysis cells.
  • Thermoelectric oxides for thermoelectric generators.
  • Development of Impedance Spectroscopy to characterise electroceramics.
Publications

Journal articles

Chapters

  • Sinclair DC (2013) CaCu3Ti4O12 (CCTO) Ceramics for Capacitor Applications, Capacitors Theory of Operation, Behavior and Safety Regulations (pp. 1-44). Nova Science Pub Incorporated RIS download Bibtex download

Conference proceedings papers

Other

Professional activities
  • Member of the EPSRC Peer Review College (Functional Materials).
  • Member of the IOM3 Materials Chemistry Committee.
  • Editorial Board Member for the Journal of Asian Ceramic Societies.