QUB will be part of a collaborative project worth £1.2 million between two US-based institutions and two counterparts in Northern Ireland and the Republic of Ireland, attempting to re-evaluate the fundamental physics of a material that has wide range of electrically functional tunabilities that enable actuators, transducers, high-energy storage capacitors and other electronic devices.

The tri-partite project involving teams from Georgia Institute of Technology (USA), University of south Florida (USA), Trinity college Dublin (Republic of Ireland) and Queen’s University Belfast aims to rediscover the underpinning science of a classic antiferroelectric material whose unique properties are useful in plethora of practical devices. The conventional theory of antiferroelectricity, developed by Kittel in 1950^s, describes antiferroelectric materials through an antiparallel arrangement of dipoles in adjacent unit cells at ground state, which switch to parallel arrangement at high applied electric fields. Such behavior has been historically associated with the perovskite structure PbZrO₃, the archetypal antiferroelectric and has profound implications towards multitude of applications in devices based on them. However, recent work on PbZrO₃ suggests a more complex picture, with a range of ferroelectric, ferrielectric and modulated polarization behavior at the nanoscale and debate about the nature of anti-ferroelectricity in this material has intensified. In this context, our team is uniquely poised to tackle the key challenges of correlated macroscopic and microscopic studies of polar and antipolar states in PbZrO₃ thin films, within the range of observation parameters. The principal scientific hypothesis of this work is in the existence of a transitional state from classical antiferroelectric states to ferroelectric and paraelectric states in the archetypal antiferroelectric PbZrO₃. This work will thus for the first time explore the effects of size reduction on such transitional states in dimension-, stress-, and orientation-controlled PbZrO₃ thin films and nanostructures. The exploration of the limits of the classical Kittel theory of antiferroelectricity will be performed through multipronged theoretical and experimental approaches, pushing the limits of the microscopy precision and informing ab-initio and DFT based atomistic modelling. The insights gained from this project would have direct relevance to broader classes of anti-ferroelectric materials. Aside from the QUB team, the project will involve Prof. Nazanin Bassiri-Gharb (Georgia Tech, USA), Prof. Sergey Lisenkov and Prof. Inna Ponomareva (USF, USA) and Prof. Lewys Jones (TCD, Republic of Ireland). The project is funded by National science Foundation (USA), Science Foundation Ireland (Republic of Ireland) and Department for Economy (Northern Ireland).

Dr. Amit Kumar, Principal investigator at QUB, says “The project is unique in the sense that the proposed work can only be conducted through the active, expert involvement of each partner in each jurisdiction. Each partner comes together in a purpose-built, mutually-beneficial collaboration, which will allow us to achieve significantly more than each one of the PIs could achieve alone or with other partners. The strength of the collaboration rests in our complementary expertise in preparation, processing, characterization and theory of ferroic materials, and analysis of the data, which will allow us to increase the research quality synergistically. The project will further advance discovery and fundamental understanding while promoting teaching, training, and learning by executing the research activities with both PhD and undergraduate students working in an international and academically stimulating environment.”

Dr. Raymond McQuaid, co-investigator on the project and UKRI Future Leaders Fellow in the school remarked “Antiferroelectrics like PbZrO₃ are also prime candidates for electrocaloric cooling and better understanding of the material physics could allow for tuning and optimisation of the electrocaloric response. My own research team at QUB is developing novel approaches to evaluate the thermal properties of materials at the nanoscale and how they can be affected and controlled by material microstructure. The lead zirconate system could offer fertile ground for investigating fundamental aspects of electrocaloric response in materials with possibilities for real world applications in solid state cooling devices"

Dr. Kristina Holsgrove, a research fellow with core expertise in ferroelectrics and high resolution Transmission Electron Microscopy will be part of the mentoring team for students working on the project. She has prior experience of working with Ultra-high resolution microscopy national and international facilities. She added “This exciting project offers a great opportunity to combine our Ewald Microscopy facility capabilities with higher resolution capabilities at TCD in a way that enables better research outcomes. Because the collaborating investigators contribute distinct expertise, the students will be exposed to many different perspectives and techniques including synthesis and processing, nanoscale structural and functional characterization, and dielectric and electromechanical property measurements.”

This research effort will result in a new understanding of antiferroelectricity at the small scale, enable the next-generation micro and nanoscale actuators and transducers that offer high force and high displacement, high-energy storage devices, miniaturized voltage regulators, solid-state cooling, electro-optic and electronic devices. Correlation of the electromechanical and electrocaloric response of these materials with the phases and parameters will enable the creation of improved miniaturized solid state cooling devices, high energy density capacitors, and micro- and nano-actuators with concomitant large displacement and large blocking force. Such actuators are fundamental for enabling the next-generation of remote controlled robotic devices in healthcare (including micro-surgery), manufacturing, agriculture, disaster management, health and rescue operations, and aerospace applications.