@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{grimley_prette_dickey_2019, title={Effect of boundary conditions on reduction during early stage flash sintering of YSZ}, volume={174}, ISSN={1359-6454}, url={http://dx.doi.org/10.1016/j.actamat.2019.05.001}, DOI={10.1016/j.actamat.2019.05.001}, abstractNote={The onset of flash sintering is generally considered to be predominantly a function of the conductivity of a given ceramic, the furnace temperature, and the electric field. However, the evolution of the point defect profiles in ionic conductors such as yttria-stabilized zirconia (YSZ) can complicate the picture of homogeneous Joule heating and thermal runaway during DC flash sintering. Here, 8 mol% YSZ pellets were partially flash sintered under a DC bias using various current densities and hold times. The electrode geometry was varied to modulate the oxygen ion flux available to the cathode to compare the effects on the resulting oxygen vacancy inhomogeneity. The contribution from fundamental and experimental factors to the cathodic reduction reaction is also discussed, such as interface reaction kinetics and sample geometry. Local reduction of the ceramic was inevitably observed under all current densities and the resulting microstructural inhomogeneity was explained as the result of a transient conductivity asymmetry. This asymmetry was the result of the enhanced electronic conductivity in the cathode region to a value significantly greater than the ionic conductivity of near-stoichiometric YSZ. The link between the local conductivity, voltage and Joule heating is mathematically demonstrated to result in an asymmetric heating profile.}, journal={Acta Materialia}, publisher={Elsevier BV}, author={Grimley, Carolyn A. and Prette, Andre L.G. and Dickey, Elizabeth C.}, year={2019}, month={Aug}, pages={271–278} }