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

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• Professor Derek C. Sinclair, Department of Materials Science and Engineering, University of Sheffield
• Tuesday 22 October 2019, 14:00-15:00
• Biosciences 301.

If you have a question about this talk, please contact Dr Dwaipayan Chakrabarti.

RSC 2019 Peter Day Award Lecture (School Seminar) hosted by Dr Paul Anderson

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.

This talk is part of the School of Chemistry Seminars series.

This talk is included in these lists:

• Biosciences 301
• School of Chemistry Seminars

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