Designing novel multiferroic materials based on the tetragonal tungsten bronze structure

Donna C. Arnold (University of Kent, UK)

The combination of the requirement for Pb-free replacements for PbZrxTi1-xO3 (PZT)[1] and the recent renaissance in multiferroics[2] has re-invigorated the investigation of ferroelectric systems. To date the main focus has been on perovskite (ABO3) based materials such as K1-xNaxNbO3 (as a Pb-free piezoelectric)[3] and BiFeO3 (best-known room temperature multiferroic)[4] due to both their compositional flexibility and also our ability to tune properties in this structure type.

The tetragonal tungsten bronze (TTB) structure, A2A'4B2B'8O30, is closely related to the perovskite structure and offers a similar degree of compositional flexibility, however the presence of crystallographically non-equivalent A- and B-sites provides an extra degree of freedom for structural manipulation. However, whilst ferroelectric TTBs were widely studied in the 1960's-70's our understanding of this structure-type is still poor.

In this seminar I will discuss our advances in understanding the structure-property relations in TTB materials, Using powder diffraction techniques and impedance spectroscopy techniques. Through controlled doping of these materials we are able o manipulate the FE transition temperature and ultimately the design of a novel multiferroic TTB material.

[1]. T. R. Shrout & S. J. Zhang (2007) J. Electroceram. 19, 111 [2]. N. A. Spaldin & M. Fiebig (2005) Science 309, 391 [3]. Y. Salto et al (2004) Nature 432, 84 [4]. M. Bibes & A. Barthelemy (2008) Nature Materials 7, 425

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