@article{zhao_funni_kmet_molina_wang_malic_dickey_jones_2024, title={Inhomogeneous domain switching near an electrode edge in orthorhombic K 0.5 Na 0.5 NbO 3 piezoceramic}, volume={246}, ISSN={["1872-8456"]}, url={https://doi.org/10.1016/j.scriptamat.2024.116089}, DOI={10.1016/j.scriptamat.2024.116089}, abstractNote={To characterize the inhomogeneous field distributions and their effect on ferroelectric/ferroelastic domain switching in potassium sodium niobate-based piezoceramics, a partially electroded orthorhombic phase K0.5Na0.5NbO3 ceramic sample containing a distinct edge was investigated using micro-beam, high-energy XRD with applied fields. Under the field application, the partial-electrode sample exhibits orientation-dependent and position-sensitive domain switching. The experimental measurements of micro-scale domain texture correlate reasonably with simulated electric fields calculated from a finite element analysis. Both experimental and simulated results reveal that the domain switching is induced inhomogeneously up to the millimeter-scale across the sample and that the electric field is significantly concentrated near the electrode edge. Integrating the experimental results with the model demonstrates that the local electric field directions and amplitudes drive the local orientation dependence of domain switching and, conversely, the direction of the local electric field can be inferred from the direction in which the maximum domain switching is measured.}, journal={SCRIPTA MATERIALIA}, author={Zhao, Jianwei and Funni, Stephen D. and Kmet, Brigita and Molina, Emily R. and Wang, Dawei and Malic, Barbara and Dickey, Elizabeth C. and Jones, Jacob L.}, year={2024}, month={Jun} }
 @article{zhao_funni_molina_dickey_jones_2022, title={Inhomogeneous electric field-induced structural changes in soft lead zirconate titanate ferroelectric ceramics}, volume={226}, ISSN={["1873-2453"]}, url={https://app.dimensions.ai/details/publication/pub.1144897101}, DOI={10.1016/j.actamat.2022.117682}, abstractNote={Under the application of an external voltage, high electric field concentrations can develop around the interdigitated electrode edges inside multilayer ceramic actuators (MLCAs). The spatial distribution of the local electrical field can create local inhomogeneity in the electromechanical response. To investigate the complex field inhomogeneity in MLCAs, partially electroded Nb-doped PbZrxTi1-xO3 samples were investigated via synchrotron-based high-energy X-ray diffraction (XRD) as a function of applied electric field. These in situ experiments allowed us to probe the structural changes as a function of position relative to the electrode edge and calculate the local degree of domain alignment, from which the local electric field directions were inferred. The domain switching behavior, both in amplitude and orientation, was found to be spatially dependent across the inactive regions in partially electroded samples. Specifically, the degree of domain alignment and field-induced phase transitions are amplified near the electrode edge. The orientation-dependent phase transitions are also amplified for the tetragonal composition near the morphotropic phase boundary (MPB), i.e., the Nb-doped PbZr0.53Ti0.47O3 composition. Finite element analysis (FEA) shows spatially-dependent, inhomogeneous electric field distributions in the partial-electrode samples, which closely match the experimentally inferred local electric field directions from XRD. The correlation of FEA and experimental data from XRD corroborates that the ferroelectric domain orientation distributions are being directed, primarily, in the direction of the electric field.}, number={ARTN 117682}, journal={ACTA MATERIALIA}, author={Zhao, Jianwei and Funni, Stephen D. and Molina, Emily R. and Dickey, Elizabeth C. and Jones, Jacob L.}, year={2022}, month={Mar} }
 @article{grimley_funni_green_dickey_2021, title={A thermal perspective of flash sintering: The effect of AC current ramp rate on microstructure evolution}, volume={41}, ISSN={["1873-619X"]}, url={https://doi.org/10.1016/j.jeurceramsoc.2020.11.040}, DOI={10.1016/j.jeurceramsoc.2020.11.040}, abstractNote={In flash sintering experiments, the thermal history of the sample is key to understanding the mechanisms underlying densification rate and final properties. By combining robust temperature measurements with current-ramp-rate control, this study examined the effects of the thermal profile on the flash sintering of yttria-stabilized zirconia, with experiments ranging from a few seconds to several hours. The final density was maximized at slower heating rates, although processes slower than a certain threshold led to grain growth. The amount of grain growth observed was comparable to a similar conventional thermal process. The bulk electrical conductivity correlated with the maximum temperature and cooling rate. The only property that exhibited behavior that could not be attributed to solely the thermal profile was the grain boundary conductivity, which was consistently higher than conventional in flash sintered samples. These results suggest that, during flash sintering, athermal electric field effects are relegated to the grain boundary.}, number={4}, journal={JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, publisher={Elsevier BV}, author={Grimley, Carolyn A. and Funni, Stephen and Green, Christopher and Dickey, Elizabeth C.}, year={2021}, month={Apr}, pages={2807–2817} }
 @article{zhao_funni_molina_dickey_jones_2021, title={Orientation-dependent, field-induced phase transitions in soft lead zirconate titanate piezoceramics}, volume={41}, ISSN={["1873-619X"]}, url={https://app.dimensions.ai/details/publication/pub.1134957541}, DOI={10.1016/j.jeurceramsoc.2021.01.043}, abstractNote={In situ high-energy X-ray diffraction (XRD) was performed on lead-zirconate-titanate-based ferroelectric materials with composition near the morphotropic phase boundary (MPB). The utilization of the two-dimensional area detector in in situ field-dependent experiments enables the complete analysis of the material response with respect to all azimuthal angles at each field amplitude. The studies reveal that the field-induced phase transition from tetragonal to rhombohedral is dependent on crystal orientation in Nb-doped PbZr0.53Ti0.47O3 that is in close compositional proximity to the MPB. However, only domain wall motion is activated in Nb-doped PbZr0.50Ti0.50O3, which is further in composition from the MPB. This synchrotron-based XRD characterization approach illustrates the importance in evaluating the orientation-dependence of phase transitions in piezoelectric and ferroelectric polycrystalline materials.}, number={6}, journal={JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, author={Zhao, Jianwei and Funni, Stephen D. and Molina, Emily R. and Dickey, Elizabeth C. and Jones, Jacob L.}, year={2021}, month={Jun}, pages={3357–3362} }