Origins of Ferroelectricity

Congratulations to former Masters student Dom Allen, whose work on ferroelectricity in MDABCO-based perovskites has just been published in the Journal of Materials Chemistry C!

MDABCO perovskites (MDABCO = N-methyl-1,4-diazoniabicyclo[2.2.2]octane) are one of a new class of ferroelectric materials, which have properties that rival best-in-class materials such as barium titanate or lead zirconate titanate. Ferroelectrics have a wide range of hugely important applications as capacitors and memory storage (e.g., in smartphones and computers), sensors, actuators and non-linear optics.

Dom’s modelling showed that the key ingredients that drive spontaneous polarisation in [MDABCO][NH4][I3] and related structures are (i) alignment of the A-site cation along <111> directions, (ii) ever-present dipolar coupling, and (iii) strain coupling between neighbouring sites. Contrary to prevailing wisdom, he found that hydrogen bonding, whilst it may still be important in determining the magnitude of polarisation or transition temperature, is actually not essential to drive this phenomenon.

The paper, which was invited for cover art, is Open Access and can be read here.

Dom’s work was supplemented by first-principles calculations from Nick Bristowe and his co-supervisor at Oxford was Andrew Goodwin. Well done all!