2021 — 2025 |
Tan, Xiaoli [⬀] Zhou, Lin |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Restricting Ferroelectric Domain Wall Motion With Volume Defects--Nanoprecipitates
NON-TECHNICAL DESCRIPTION: Piezoelectric ceramics are functional materials that develop electric charges when subjected to mechanical forces and change their dimensions when subjected to electric fields. Such conversion of energies between mechanical and electric forms can have extremely high efficiency (up to 90%); and hence, these ceramics have widespread applications in critical technologies such as SONAR, medical imaging, and non-destructive evaluation. Currently, the technique to manipulate and improve their functional properties is to introduce impurity atoms in the ceramic. However, this technique has reached its fundamental limit. The current project explores a radically new mechanism -- introducing highly dispersed impurity nanocrystals (~50 nm) into the bulk ceramic -- to further improve the performance of piezoelectric ceramics and allow them to function at higher temperatures and under higher electric fields. These improved ceramics can then be used to create next generation high-power devices that operate under more extreme conditions. In addition to technical contributions, this project also provides learning and career advancement opportunities for many communities. Both graduate and undergraduate students, many of whom from underrepresented groups, are involved in this project; graduates who study ceramics science can typically find employment in national labs and industry sectors of microelectronics and manufacturing; and various demonstrations on piezoelectric technologies are given to K-12 students to encourage scientific thinking and spark interest in science and engineering fields.
TECHNICAL DETAILS: This project aims to establish a novel mechanism of stabilizing the domain structure and hardening piezoelectric ceramics with nanoscale coherent precipitates. Compared to the state-of-the-art point-defect technique, volume defects provide stronger restrictions and are stable under higher temperatures. Therefore, this project helps realize high-power piezoelectric transducers that can be used at higher driving frequencies and vibration velocities. As a model system, this project focuses on lead-free BaTiO3/CaTiO3 compositions, where slanted solvus lines in the phase diagram guide the precipitation of uniformly dispersed nanoscale coherent crystals in bulk polycrystalline ceramics. Presumably, the CaTiO3-rich precipitate remains non-polar when it is larger than a critical size and becomes polar when it is below the critical size. The ferroelectric domain wall in the BaTiO3-rich matrix is hypothesized to be restricted in different modes by precipitates of different sizes. The hypotheses are directly verified using the in-situ heating and biasing, and other advanced transmission electron microscopy techniques. Both graduate and undergraduate students are involved in this project and are trained with ceramic manufacturing and property characterization. The doctoral student is further trained with cutting-edge transmission electron microscopy techniques, which are used to characterize precipitate/matrix interfaces at the atomic level in terms of chemistry, displacement, strain, and charge.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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