Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New acoustic technique reveals structural information in nanoscale materials


Understanding where and how phase transitions occur is critical to developing new generations of the materials used in high-performance batteries, sensors, energy-harvesting devices, medical diagnostic equipment and other applications. But until now there was no good way to study and simultaneously map these phenomena at the relevant length scales.

Now, researchers at the Georgia Institute of Technology and Oak Ridge National Laboratory (ORNL) have developed a new nondestructive technique for investigating these material changes by examining the acoustic response at the nanoscale. Information obtained from this technique - which uses electrically-conductive atomic force microscope (AFM) probes - could guide efforts to design materials with enhanced properties at small size scales.

This is a schematic representation of the atomic force microscope interacting with the material surface.

Credit: Rama Vasudevan, ORNL

The approach has been used in ferroelectric materials, but could also have applications in ferroelastics, solid protonic acids and materials known as relaxors. Sponsored by the National Science Foundation and the Department of Energy's Office of Science, the research was reported December 15 in the journal Advanced Functional Materials.

"We have developed a new characterization technique that allows us to study changes in the crystalline structure and changes in materials behavior at substantially smaller length scales with a relatively simple approach," said Nazanin Bassiri-Gharb, an associate professor in Georgia Tech's Woodruff School of Mechanical Engineering. "Knowing where these phase transitions happen and at which length scales can help us design next-generation materials."

In ferroelectric materials such as PZT (lead zirconate titanate), phase transitions can occur at the boundaries between one crystal type and another, under external stimuli. Properties such as the piezoelectric and dielectric effects can be amplified at the boundaries, which are caused by the multi-element "confused chemistry" of the materials. Determining when these transitions occur can be done in bulk materials using various techniques, and at the smallest scales using an electron microscope.

The researchers realized they could detect these phase transitions using acoustic techniques in samples at size scales between the bulk and tens of atoms. Using band-excitation piezoresponse force microscopy (BE-PFM) techniques developed at ORNL, they analyzed the resulting changes in resonant frequencies to detect phase changes in sample sizes relevant to the material applications. To do that, they applied an electric field to the samples using an AFM tip that had been coated with platinum to make it conductive, and through generation and detection of a band of frequencies.

"We've had very good techniques for characterizing these phase changes at the large scale, and we've been able to use electron microscopy to figure out almost atomistically where the phase transition occurs, but until this technique was developed, we had nothing in between," said Bassiri-Gharb. "To influence the structure of these materials through chemical or other means, we really needed to know where the transition breaks down, and at what length scale that occurs. This technique fills a gap in our knowledge."

The changes the researchers detect acoustically are due to the elastic properties of the materials, so virtually any material with similar changes in elastic properties could be studied in this way. Bassiri-Gharb is interested in ferroelectrics such as PZT, but materials used in fuel cells, batteries, transducers and energy-harvesting devices could also be examined this way.

"This new method will allow for much greater insight into energy-harvesting and energy transduction materials at the relevant length sales," noted Rama Vasudeven, the first author of the paper and a materials scientist at the Center for Nanophase Materials Sciences, a U.S. Department of Energy user facility at ORNL.

The researchers also modeled the relaxor-ferroelectric materials using thermodynamic methods, which supported the existence of a phase transition and the evolution of a complex domain pattern, in agreement with the experimental results.

Use of the AFM-based technique offers a number of attractive features. Laboratories already using AFM equipment can easily modify it to analyze these materials by adding electronic components and a conductive probe tip, Bassiri-Gharb noted. The AFM equipment can be operated under a range of temperature, electric field and other environmental conditions that are not easily implemented for electron microscope analysis, allowing scientists to study these materials under realistic operating conditions.

"This technique can probe a range of different materials at small scales and under difficult environmental conditions that would be inaccessible otherwise," said Bassiri-Gharb. "Materials used in energy applications experience these kinds of conditions, and our technique can provide the information we need to engineer materials with enhanced responses."

Though widely used, relaxor-ferroelectrics and PZT are still not well understood. In relaxor-ferroelectrics, for example, it's believed that there are pockets of material in phases that differ from the bulk, a distortion that may help confer the material's attractive properties. Using their technique, the researchers confirmed that the phase transitions can be extremely localized. They also learned that high responses of the materials occurred at those same locations.

Next steps would include varying the chemical composition of the material to see if those transitions - and enhanced properties - can be controlled. The researchers also plan to examine other materials.

"It turns out that many energy-related materials have electrical transitions, so we think this is going to be very important for studying functional materials in general," Bassiri-Gharb added. "The potential for gaining new understanding of these materials and their applications are huge."


This research was supported by the National Science Foundation (NSF) through grant DMR-1255379. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility at ORNL. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NSF or DOE.

CITATION: Rama K. Vasudevan, et al., "Acoustic Detection of Phase Transitions at the Nanoscale," (Advanced Functional Materials, 2015).

Media Contact

John Toon


John Toon | EurekAlert!

More articles from Materials Sciences:

nachricht From ancient fossils to future cars
21.10.2016 | University of California - Riverside

nachricht Study explains strength gap between graphene, carbon fiber
20.10.2016 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>