Designing a new material for improved ultrasound

March 22, 2018, Pennsylvania State University
A long-range ferroelectric domain with nanoscale structure heterogeneity (4-8 nm) is evidenced by high-resolution TEM. Credit: Fei Li/Penn State

Development of a theoretical basis for ultrahigh piezoelectricity in ferroelectric materials led to a new material with twice the piezo response of any existing commercial ferroelectric ceramics, according to an international team of researchers from Penn State, China and Australia.

Piezoelectricity is the material property at the heart of medical ultrasound, sonar, active vibration control and many sensors and actuators. A piezoelectric material has the ability to mechanically deform when an electric voltage is applied or to generate electric charge when a mechanical force is applied.

Adding small amounts of a carefully selected rare earth material, samarium, to a high-performance piezoelectric ceramic called lead magnesium niobate-lead titanate (PMN-PT) dramatically increases its piezo performance, the researchers report in Nature Materials this week. This materials-by-design strategy will be useful in designing materials for other applications as well, the team believes.

"This is not the typical way to develop new materials," said the team's co-corresponding author, Long-Qing Chen, Donald W. Hamer Professor of Materials Science and Engineering, professor of mathematics, and professor of engineering science and mechanics, Penn State. "The majority of existing useful are discovered by trial-and-error experiments. But here we designed and synthesized a new piezoelectric ceramic guided by theory and simulations."

The team first analyzed the impact of adding various chemical dopants on the local structure of an existing ferroelectric ceramic. They were then able to reduce the pool of effective dopants by comparing the measured dielectric losses with the signatures obtained from phase-field simulations. After the screening of dopants, they then focused on optimizing the process and composition to achieve the ultrahigh piezoelectricity.

"This work is based on an understanding of the origin of ultrahigh piezoelectricity in the ferroelectric crystals that were developed 30 years ago. Our new understanding suggested that local structure heterogeneity plays an important role in piezoelectricity in ferroelectrics, which also can be extended to other functionalities," said co-corresponding author Shujun Zhang, a professor of formerly at Penn State and now at the University of Wollongong in Australia.

Local structure heterogeneity refers to nanoscale-size structural distortions within a host material created by doping a small amount of chemical species, in this case doping samarium in PMN-PT ceramics, as a way to modify the thermodynamic energy landscape of the material, which in turn increases the dielectric properties—the ability of a material to respond to an electrostatic field—and the piezoelectric effect.

"This material is a good choice to use in transducers, such as those used in medical ultrasound," said lead author Fei Li, a research associate at Penn State. "We already have devices made from our material by a group at the University of Southern California."

That device, called a needle transducer, uses a submillimeter piezoelectric element of the Penn State material, fitted into a standard needle or catheter, in order to perform minimally invasive procedures, to image inside the body or to guide precision surgery inside the body. The device has better performance than existing devices with the same dimensions, Li said.

Penn State has filed a provisional patent on the material.

Explore further: The origin of ultrahigh piezoelectric response

More information: Ultrahigh piezoelectricity in ferroelectric ceramics by design, Nature Materials (2018). DOI: 10.1038/s41563-018-0034-4 , https://www.nature.com/articles/s41563-018-0034-4

Related Stories

The origin of ultrahigh piezoelectric response

January 10, 2017

All ferroelectric materials possess a property known as piezoelectricity in which an applied mechanical force can generate an electrical current and an applied electrical field can elicit a mechanical response. Ferroelectric ...

Negative piezoelectric effect is not so rare after all

November 30, 2017

(Phys.org)—The piezoelectric effect, which causes a material to expand along the direction of an applied electric field, is common in many materials and used in a variety of technologies, from medical ultrasound to vibration-powered ...

The fine-tuning of two-dimensional materials

February 28, 2018

A new understanding of why synthetic 2-D materials often perform orders of magnitude worse than predicted was reached by teams of researchers led by Penn State. They searched for ways to improve these materials' performance ...

Recommended for you

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.