New and Improved Electroceramics

Lead Research Organisation: University of Sheffield
Department Name: Materials Science and Engineering

Abstract

This Large Grant proposal combines the expertise of Sheffield and Leeds to establish a major electroceramics research hub. Electroceramics are advanced materials whose properties and applications depend on close control of crystal structure, chemical composition, ceramic microstructure, dopants and dopant (or defect) distribution. In most cases, properties depend on a complex interplay of structural, processing and compositional variables. They find applications in various physical forms, eg as ceramic discs, thick and thin films and multi-layer devices consisting of alternating layers (up to several hundred) of ceramic and metal electrodes. The particular property of interest may be a bulk property of the crystals, for example, high levels of ionic conductivity, mixed electronic-ionic conduction, ferro-, pyro- piezo-electricity or ferrimagnetism. Alternatively, it may relate specifically to the grain boundaries (or surface layers) in polycrystalline materials and to small differences in composition and therefore electrical behaviour between the bulk and grain boundary (or surface) regions. Such heterogeneous, or functionally-graded ceramics find many applications eg non-ohmic devices in current limiters such as varistors and thermistors. This proposal focuses on new and improved electroceramics for potential near- and long-term applications. The work will be carried out by a multidisciplinary team with complementary skills in materials discovery, modelling, processing and advanced characterisation. Such a multifaceted approach to electroceramics research and development does not exist in the UK within a single institution and the establishment of a 'hub' between the two universities will allow us to compete with the best in the world. Three work packages are proposed.I. New and improved bulk materials: structure-property relations, including: (a) novel perovskite-type materials with targeted functionality: ferroelectricity, reversible electro-strain, piezoelectricity, magneto-electric coupling and mixed conductivity; (b) development of new low temperature co-fired ceramics based on Sillenites; (c) oxygen nonstoichiometry and core-shell phenomena in doped BaTiO3; (d) development of improved lithium battery cathodes based on layered rock salt structures. II. Materials processing and development in thin and thick film form, including:(a) BiFeO3-PbTiO3 and BiMeO3 thin films for ferroelastic/ferroelectric switching for actuator and memory applications; (b) thin film feasibility studies on Solid Oxide Fuel Cell structures; (c) thick and thin films based on the novel ferroelectric system Ba2RETi2Nb3O15 to assess their potential device applications; (d) development of a masked Electrophoretic Deposition technique to deposit planar magnetoelectric composites based on Pb(Zr,Ti)O3-Pb(Ni,Nb)O3 (soft piezoelectric) and (La,Ca)MnO3 (magnetostrictor). III. Modelling of bulk materials and interfacial phenomena: (a) Development of Finite Element modelling of current pathways in (i) heterogeneous ceramics, (ii) local probe measurements within grains and across individual grain boundaries and (iii) multilayer devices; the results will be used to simulate Impedance Spectroscopy data and allow comparison with, and interpretation of, experimental data; (b) Modelling of functional oxides: point defects, electronic band structure calculations and mass diffusion in ceramics; this will underpin the experimental programmes on the development of new materials and the role of dopants in existing materials. Work packages I and II will be supported by a wide range of characterisation techniques available at Leeds and Sheffield for studying bulk and interfacial phenomena. New characterisation techniques will be applied: aberration-corrected TEM allows true atomic scale spectroscopy of interfaces and defects; Kelvin Probe Microscopy gives direct imaging of the work function variation in grain and across grain boundary regions.

Publications

10 25 50
 
Description Ian Reaney (IR): The part of the grant for which IR was directly responsible concerned materials processing. The major breakthrough in this area was the establishment of multilayering technology at Sheffield via Denis Cummings (PDRA). This facility generated several articles in referreed journals but importantly has become the backbone of the group in terms of prototype device capability and feeds into many projects including the recently awarded grant 'Substitution and Sustainability in Functional Materials'
Anthony West (AW): The main discovery is the effect of bias voltage on the electrical properties of bulk ceramic materials that have been doped by an acceptor mechanism. Six publications have followed on alkaline earth titanates with the perovskite structure and one on doped bismuth ferrite which shows a remarkable insulator-metal transition at room temperature. This work is likely to expand to consider situations under which oxygen in oxides can be redox active

John Harding (JH) was responsible for the modelling part of the grant. Working in collaboration with Derek Sinclair (DS) the modelling showed that the widely accepted mechanism to produce semiconducting grains (direct donor-doping) in PTCR BaTiO3-based thermistors is incorrect and demonstrated an alternative based on Ti vacancies. We have made a major code development to analyse impedance spectra. A fast, efficient finite element code now enables direct analysis (i.e. no equivalent circuits) of impedance spectra for three dimensional heterogeneous ceramics with realistic micro-structures of ceramics and incorporating contacts, grain boundaries, and grain cores.
Derek Sinclair (DS) developed structure-composition-property relationships in several important perovskite-type oxides. Particular emphasis was given to the electrical properties that ranged from dielectrics to semiconductors to ionic conductors. Systems studied included A-site ordered perovskites such as CaCu3Ti4O12, B-site deficient hexagonal perovskites such as Ba3LaNb3012 and A-site disordered cubic type (Na,Bi)TiO3 (NBT). A major discovery in this work was high levels of oxide-ion conductivity in NBT and this has led to the development of a new family of oxide ion conductors with potential as electrolytes for intermediate temperature solid oxide fuel cells.
Exploitation Route AW: The discovery of voltage-dependent conductivity of electrical properties should impact on a number of areas, including dielectric breakdown of insulating ceramics, mechanisms of memristive switching and the onset of flash sintering, all of which are pursued by numerous research groups elsewhere.IR: The tapecasting/screen printing methodologies introduced by this grant have been shown to be very useful for projects ranging from the development of thermoelectric generators to carbon capture and utilisation; these are either planned or in progress.

JH: The finite element code will be of wide utility for impedance spectra analysis and can be extended to consider thermistors and piezoelectric systems.

DS: The discovery of oxide-ion conductivity in NBT was unexpected and raises the potential for other new families of Bi-based perovskites oxide as a new class of solid electrolytes. These materials may have applications in Solid Oxide Fuel Cells.
Sectors Aerospace, Defence and Marine,Education,Electronics,Energy

 
Description IR: The major findings in establishing a tape casting/screen printing capability have been used to generate significant amounts of further funding and have become intrinsic to Sheffield's research portfolio, generating >£3M in related projects AW: Recognition of the voltage-dependence of p-type semiconductivity in some ceramic oxides and attribution of its origin to redox-active oxygen has changed my perspective of p-type semiconduction. Grant applications have been submitted as a direct consequence with results awaited on SOCRATES (epsrc: degradation of fuel cells call), DOLORES (EU Marie-Curie fellowship application) and NORA (EU Advanced fellowship application). DS- The initial NBT results on oxide-ion conduction have generated a follow up EPSRC grant award (due to start Dec 2014) to optimise the electrical properties in this system and to explore the possibility of using NBT as a bilayer electrolyte component for intermediate temperature solid oxide fuel cells.
First Year Of Impact 2012
Sector Aerospace, Defence and Marine,Education,Electronics,Energy
Impact Types Economic

 
Description EPSRC RESPONSIVE MODE GRANT
Amount £467,000 (GBP)
Funding ID EP/L027348/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 11/2014 
End 10/2017
 
Description Global Challenges PhD studentship
Amount £60,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 10/2013 
End 09/2017
 
Description Marie-Sklodowska-Curie Individual Fellowships
Amount £138,981 (GBP)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 10/2016 
End 09/2018
 
Description Materials for Demanding Environments
Amount £139,200 (GBP)
Funding ID 67856-475270 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 05/2016 
End 04/2017
 
Description Royal Academy of Engineering Distinguished Visitor
Amount £6,000 (GBP)
Organisation Royal Academy of Engineering 
Sector Learned Society
Country United Kingdom
Start 04/2017 
End 11/2017
 
Description Centre for Dielectrics and Piezoelectrics (CDP 
Organisation Center for Dielectrics & Piezoelectrics
PI Contribution Centre for Dielectrics and Piezoelectrics (CDP). Sheffield has now been voted in as an Affiliate Partner in the NSF funded CDP alongside North Carolina State University (NCSU) and Pennsylvania State University (PSU. The CDP has ~25 members which include Samsung, Apple, Murata and 3M. The joint grant with PSU was instrumental in cement our relationship with the centre based on a number of high profile publications with the CDP co-director Susan Mckinstry (international CoI on grant)
Collaborator Contribution Susan McKinstry and Ian M. Reaney are now co-directors of the CDP. The publications helped demontrate to the Industrial Members the strength of the partnership between the CDP and Sheffield
Impact Multidisciplinary. Ceramic Engineering, Life Cycle Assessment, Materials Modelling. Has led to joint projects, research, secondments and industrial funding
Start Year 2017
 
Title High Temperature Piezoelectric Ceramics 
Description A patent has been filed by Professor Bell, Leeds University, in multiple territories covering new piezoelectric compositions with properties comparable to the market leader, PZT, but with a much wider operating temperature window. 
IP Reference EP11738766.6 
Protection Patent application published
Year Protection Granted 2014
Licensed No
Impact This is an ongoing research area at Leeds to find alternative, lead-free piezoelectric materials
 
Title Polymer electrolyte -Polymer 1 copolymer 
Description A new polymer - salt composite material was developed with a very high level of lithium ion conductivity 
IP Reference GB2401608 
Protection Patent application published
Year Protection Granted
Licensed No
Impact This has lead other research groups, worldwide, to consider such materials
 
Title SELF-HEALING COMPOSITE MATERIAL 
Description Self-healing composites that are used in aircraft wing structures 
IP Reference GB2421953 
Protection Patent granted
Year Protection Granted
Licensed No
Impact Not known as the pi responsible retired 5 years ago
 
Company Name Ionix Advanced Technologies Ltd 
Description Spin-out company formed to exploit IP from the project 
Year Established 2011 
Impact It is now an established organisation providing commercial high temperature electroceramics
 
Company Name Ionix Advanced Technologies Ltd 
Description The company exploits unique University of Leeds IP on high temperature piezoelectric materials through the design, manufacture and sales of high temperature ultrasound transducers for structural health monitoring, non-destrcutuive evaluation and industrial process control. 
Year Established 2011 
Impact Too soon to describe
Website http://www.ionix.at