NON-TECHNICAL DESCRIPTION: Ferroelectric materials (which have a spontaneous polarization which can be reoriented by an applied electric field – the electrical analog of ferromagnetic materials) comprise a multi-billion-dollar industry; in nearly every case, the functional properties depend on the mobility of domain walls (the boundaries between regions with different polarization directions). This project is quantifying the role of realistic microstructure on the mobility of these domain walls, and broadly disseminating these results to the scientific community and industry. At the graduate level, the project is training students who will become next-generation scientific and technology leaders. Graduates typically find employment either at high-tech companies or as university faculty members. In addition, the principal investigator will complete a second edition of the textbook, Materials Engineering: Bonding, Structure, and Structure-Property Relationships.
TECHNICAL DETAILS: The fundamental processes and length scales associated with pinning domain wall and phase boundary motion in ferroelectric materials are at present poorly understood for general cases. This project is using a combination of electrical and electromechanical characterization, transmission X-ray microscopy, nanoprobe X-ray scattering, and piezoresponse force microscopy to develop a quantitative database on the way that different mechanical boundary conditions, including film stress, grain boundary misorientation angle, and interacting crystallographic defects influence correlated motion of domain walls. The interdisciplinary team of researchers from Penn State, Argonne National Laboratories and the Technical University of Denmark are preparing and characterizing model samples with a wide range of different grain boundary angles in order to directly measure the length scales over which correlated motion of domain walls occurs in Pb(Zr,Ti)O3 thin films. The functional properties are being mapped through a combination of Rayleigh and Preisach approaches. Large area measurements are being complemented with local measurements via piezoresponse force microscopy to map the size of the clusters where there is collective motion of domain walls for different strain states and grain boundary misorientations. Samples are being interrogated with nanoprobe diffraction measurements under field excitation. Moreover, the local domain structure in regions identified as strongly or weakly responsive are being interrogated via X-ray dark field microscopy in order to spatially map the defect/domain wall interactions. The ability to localize the major pinning sites and then structurally probe those regions non-destructively while exciting the sample electrically allows the possibility of elucidating the impact of local perturbations on the collective motion of functional domain walls. These results are allowing models of ferroelectric films, ceramics, and single crystals to be developed to capture the fundamental material physics more accurately.
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.
|Effective start/end date||8/1/20 → 7/31/24|
- National Science Foundation: $448,751.00