researchers at the argonne national laboratory (chicago, ill.) have developed a novel approach for the study of piezoelectric materials that uses ultrafast, 3-d x-ray imaging and computer modeling to better understand the material behavior of these materials, according to a report from the argonne lab.

participating authors behind the study include researchers at the center for
nanoscale materials, the advanced photon source and argonne’s x-ray science
division. (mark lopez/argonne national laboratory)

by gaining a better understanding of how these materials work, researchers are hoping to design more powerful and more energy-efficient piezoelectric technologies, which are found in numerous consumer electronics like fitness trackers, wearables, and medical devices.

in particular, the research team focused on zinc oxide, which generates electricity if it is twisted, bent or deformed in any way. the article noted that zinc oxide has emerged as a promising material to generate electricity in small-scale devices.

the article continued, “in their experimental approach, known as ultrafast x-ray coherent imaging, researchers took a nanocrystal of zinc oxide and exposed it to intense, short x-ray and optical laser pulses at argonne’s advanced photon source, a doe office of science user facility. the ultrafast laser pulses excited the crystal, and the x-ray pulses imaged the crystal structure as it changed over time. this enabled researchers to capture very small changes in the material at a high resolution in both time and space.”

this allowed researchers to see inside the material as it was bent and twisted and they were able to identify deformation modes (ways in which the material could be deformed). this will lead to the construction of a model describing the material’s behavior.

“with this model, researchers discovered additional twisting modes that can generate 50 percent more electricity than the bending modes of the crystal,” the article added.

it continued, “combining modeling and experimental approaches can also help researchers explore various other material systems and processes, such as corrosion and heat management across thermal devices. such work will also be advanced with the upgrade of the advanced photon source, which will increase the flux of the facility’s high-energy coherent x-ray beams by 150-fold.”

the research was published in nano letters. the abstract stated:

“imaging the dynamical response of materials following ultrafast excitation can reveal energy transduction mechanisms and their dissipation pathways, as well as material stability under conditions far from equilibrium. such dynamical behavior is challenging to characterize, especially operando at nanoscopic spatiotemporal scales.

“in this letter, we use x-ray coherent diffractive imaging to show that ultrafast laser excitation of a zno nanocrystal induces a rich set of deformation dynamics including characteristic “hard” or inhomogeneous and “soft” or homogeneous modes at different time scales, corresponding respectively to the propagation of acoustic phonons and resonant oscillation of the crystal.

“by integrating the 3d nanocrystal structure obtained from the ultrafast x-ray measurements with a continuum thermo-electro-mechanical finite element model, we elucidate the deformation mechanisms following laser excitation, in particular, a torsional mode that generates a 50% greater electric potential gradient than that resulting from the flexural mode.

“understanding of the time-dependence of these mechanisms on ultrafast scales has significant implications for development of new materials for nanoscale power generation.”

the researchers also released a video of the imaging that can be viewed below: