1. National Science Foundation Outcome: Researchers at the University of Florida have directly measured the mechanism that creates frequency-dependent material properties in piezoelectric oxides, proving a decades-old hypothesis regarding its origin. Impact: Understanding the origin of the frequency dispersion will now allow researchers to focus on controlling or mitigating this frequency dispersion, enabling better control of electromechanical actuators for biomedical, defense, and consumer electronics. Explanation: Ferroelectric domain walls are defects in oxide materials. Their motion within the materials during electric field application gives rise to hysteresis and frequency-dispersion of the electric-field-induced properties such as piezoelectricity. Professor Jones and his team of students have used diffraction from crystal planes during electric field application to capture the materials behavior in situ. Origin of frequency-dependent piezoelectricity Jacob L. Jones, University of Florida, DMR 0746902 Prof. Jones and his students and international collaborators (above) used the diffraction of neutrons from a nuclear reactor to measure the material response during dynamic electric field loading.

2. National Science Foundation Origin of frequency-dependent piezoelectricity Jacob L. Jones, University of Florida, DMR 0746902 The piezoelectric effect enables the conversion of electric fields or voltages into mechanical strain or displacement. Materials exhibiting this effect are used in electronic devices as physical sensors, actuators, and vibrational energy harvesting devices. At frequencies across many orders of magnitude, e.g. between 1 mHz to 1 MHz, many ferroelectric materials exhibit dispersion in the elastic, dielectric, and piezoelectric property coefficients, sometimes exceeding 50% across a few decades in frequency. Investigators at the University of Florida, led by Professor Jacob Jones, have utilized time-resolved neutron diffraction from the crystalline lattice of several different piezoelectric materials to prove that the physical origins of this response comes from the motion of ferroelectric domain walls. The angularly resolved diffracted neutrons (top figure) are measured with time resolution during application of cyclic electric fields of various frequencies. The characteristic changes in the pattern (e.g., position – bottom figure) are a signature of the frequency-dependent material response.

3. National Science Foundation The US national laboratories are a significant national financial and intellectual investment. This undergraduate training experience enabled undergraduate students to travel to these facilities and collaborate with scientists as part of their undergraduate university-based research projects. This experience, called “Partnering Undergraduate Research with National Laboratories” enabled 10 undergraduate students to participate in experiments at national synchrotron and neutron diffraction facilities at national laboratories, including Argonne National Laboratory and Oak Ridge National Laboratory. Their visit to national laboratories either encouraged or reinforced their original desires to pursue graduate school. Undergraduate Research at National Laboratories Jacob L. Jones, University of Florida, DMR 0746902 Undergraduate students Cassandra Llano (top, far right) and Jared Carter (bottom) are two of the students who participated in this program. Both will pursue advanced degrees.