Potential Advances in Flexible Electronics Could Now Be Looming Thanks to Penn State Research

The theory that underpins the mechanism of so-called relaxor ferroelectrics has been a topic of debate for over five decades.

According to Qing Wang, a professor of materials science and engineering at Penn State University—the ferroelectric polymers' relaxor behavior originates from conformational disorder, completely different from classic perovskite relaxors, which are typically characterized by a chemical disorder.

The team has given rise to relaxor properties in polymers, which could lead to the discovery of new ferroelectric relaxor organic materials for use in flexible, scalable, and biocompatible electrical applications like sensors and batteries. 

 

A New Understanding of Ferroelectric Behavior 

Due to the lack of a fundamental understanding of the mechanism, not much progress has been made in designing new relaxor ferroelectric materials despite all the promise that they hold. However, the team claims that their new understanding, which relies on experiments and theoretical modeling, shows that relaxor ferroelectricity in polymers stems from chain confirmation disorders induced by chirality, a feature of many organic materials where molecules are mirror images of one another (but not the same). In contrast, the relaxor mechanism in polymers is vastly different.

"Unlike ferroelectrics, relaxors exhibit no long-range, large ferroelectric domains but disordered local polar domains," Wang explained. "The research in relaxor polymeric materials has been challenging due to multiple phases such as crystalline, amorphous, and crystalline-amorphous interfacial area in polymers." 

 

An MRI showing chiral molecules that give relaxor ferroelectrics their desirable properties. Image credited to Penn State University

 

Relaxors in Energy Storage

In energy storage applications, relaxors can deliver a higher energy density than normal ferroelectrics, which have a high ferroelectric loss and waste more energy through heat. In addition, relaxors can generate more strain under the applied electric fields and thus have a much better energy conversion efficiency than normal ferroelectrics. Together, these make relaxors a better material for actuators and sensors. 

This work builds on a rich research history in ferroelectric materials at Penn State. In 1998, the first relaxor ferroelectric polymer was discovered here. "The new understanding of relaxor behavior would open up unprecedented opportunities for us to design relaxor ferroelectric polymers for a range of energy storage and conversion applications," said Wang.