Tuneable properties in titanate-based perovskites: from 'fast ion' conduction to 'weakly temperature dependent' ferroelectric relaxors.

Tuneable properties in titanate-based perovskites: from 'fast ion' conduction to 'weakly temperature dependent' ferroelectric relaxors.
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This is a past event

Professor Derek Sinclair, University of Sheffield. Royal Society of Chemistry Peter Day Award 2019 lecture.

Ferroelectricity is a common phenomenon in (do) titanate-based perovskites such as BaTiO3, (Na1/2Bi1/2)TiO3 and Pb(Zr,Ti)O3. These materials are commercially important electroceramics with applications as high permittivity dielectrics and piezoelectrics in multi-layer ceramic capacitor (MLCC) and/or actuators: over 3 Trillion BaTiO3-based MLCC’s were produced last year. Their electrical properties can be manipulated in many ways, for example by small changes in stoichiometry, formation of solid solutions with other (often high pressure) perovskites and inter- and intra-granular segregation of dopants. We illustrate some of these mechanisms using (Na1/2Bi1/2)TiO3 (NBT) and (BaTiO3)1-x-(BiScO3)x (BT-BS) as examples. In particular, how:-

(i) remarkably small changes in the Na,Bi content in NBT can transform this dielectric material into an unexpected and excellent oxide-ion conductor and we will discuss the possibility of a limit to the level of oxide-ion conduction that can be obtained in the perovskite lattice. 

(ii) donor and/or acceptor-doping of the NBT lattice can be used to control the level of defects and therefore ‘tune’ the electrical properties from oxide-ion conduction (type I) via mixed ionic-electronic conduction (type II) to polar dielectric behaviour (type III).

(iii) forming a solid solution between BT-BS can transform a classic ferroelectric (BT) with very temperature dependent permittivity behaviour into a weakly temperature dependent ferroelectric relaxor with high permittivity (~ 1000) over a remarkably wide temperature range (~ 100 – 400 oC).

In many cases, Impedance Spectroscopy has been used to probe the electrical properties and we will discuss the advantages and challenges in using this technique to characterise electroceramics. In particular, we highlight how finite element modelling is assisting with the development of data analysis.

Speaker
Professor Derek Sinclair
Hosted by
Professor Jan Skakle
Venue
Meston Lecture Theatre 6