Improper and Incommensurate/Commensurate Ferroelectrics
Main list: Cond Mat Seminars
Ferroelectric materials have long been exploited in wide range of electronic devices including capacitors, actuators, sensors and memory chips. These devices typically utilise the macroscopic properties of ferroelectrics related to their spontaneous polarisation, i.e. high relative permittivity, electromechanical (piezo-) and thermal pyro-electric) properties. Ferroelectrics, however, commonly consist of domains (regions of common polarisation orientation) separated at their interface by domain walls. Although domains and domains walls have been known for many years they have largely remained an academic curiosity. More recently, ferroelectric domain walls have been shown to exhibit properties different to those exhibited by the bulk; exploitation of domain wall functionality in ferroelectrics has led to the emerging field of domain wall nanoelectronics.Our research interests lie in the development of novel ferroelectric materials and understanding of their composition-structure-property relations. Recently we have focussed on ferroelectrics likely to exhibit complex domain structures and give rise to emergent domain walls properties; these materials include improper ferroelectrics and also proper ferroelectrics which exhibit instabilities such as structural disorder and incommensurate modulations. I will give an update on our recent studies on: a) improper ferroelectricity in the hexagonal tungsten bronze CsNbW2O9 which displays a complex labyrinthine domain structure including six-fold domain vertices ); b) the role of composition and structural disorder in tetragonal tungsten bronzes [2,3]; and c) a incommensurate-commensurate transition in LaTaO4. Adv. Mater., 31, 1903620, 2019. Chem. Mater., 27, 3250, 2015. Chem. Mater., 28 (13), 4616-4627, 2016.
University of St Andrews
November 13, 2019
From: 13h00 To: 14h00