Dr. Jon Spanier

Drexel University 

Friday, April 19, 2024
12:00 Noon
Room 120 – Meyerhoff Chemistry Building
Host: Dr. Joe Bennett

“Ferroelectric domain wall dynamics”

Ordering of ferroelectric polarization and its trajectory in response to an electric field are essential for the operation of transducers, non-volatile memories and electro-optic devices. However, for voltage control of capacitance and frequency, domain walls have long been thought to be a hindrance because they lead to high dielectric loss and hysteresis in response to an applied electric field. To avoid these effects, tunable dielectrics are often operated under piezoelectric resonance conditions, relying on operation well above the ferroelectric Curie temperature, where tunability is compromised. Therefore, there is a seemingly unavoidable trade-off between the requirements of high tunability and low loss in tunable dielectric devices, which leads to severe limitations on their figure of merit.

At the same time, realization of tunable materials that are multifunctional and maintain high performance in dynamically changing environments is a fundamental goal of materials science and engineering. Tunable dielectrics form the basis of a wide variety of microwave, sub-mm and mm-wave communication and sensing devices, and require breakthrough performance improvement to enable next-generation technologies. Engineering the ferroelectric polarization-energy landscape offers intriguing new opportunities for tailoring properties.

I will discuss our re-examination of the ferroelectric polarization-energy landscapes associated with domain walls and their motion. We use intrinsically tunable materials with properties that are defined not only by their chemical composition, but also by the proximity and accessibility of thermodynamically predicted strain-induced, ferroelectric domain-wall variants. Starting from application of Ginzburg-Landau-Devonshire theory, under special conditions we predict and observe extraordinarily high dielectric tunability and the emergence of dynamic behavior that remarkable resonant responses.  I will also present our recent work to design and model the domain structure-property relationships of film materials that exhibit exceptionally large tunable dielectric response over a wide temperature range and feature tunability that is itself controllable. These results suggest that domain engineering is a powerful approach for achieving unprecedented modulation of functional properties in ferroelectric films.