Study of flash phenomena on single crystals of cubic 8 mol% yttria stabilized zirconia
March 10-15, 2019
Flash sintering has recently emerged as a low energy technique for ultra-rapid densification of ceramics at remarkably low temperatures. Dense polycrystals also exhibit the flash phenomena; of course, they do not sinter. We carried out the flash experiments on single crystals of cubic zirconia and measured the temperature for the onset of flash as a function of electric field. The results were compared with flash sintering experiments on powders of cubic zirconia. The single crystals flash at lower temperatures and lower electric fields compared to that with the powders samples. The results indicate that particle-particle interface and grain boundaries are not necessary for instigating flash and that flash is more likely a matrix effect. The flash onset in single crystals occurs at similar values of the power density as the powder samples, and the values of power density, at the flash onset lies in the same range as in several oxides. The activation energy for specific conductivity, at the flash transition, was lower than for oxygen ion diffusion in zirconia. With the flash experiments at very high electric fields, on the dense polycrystals, we found that the temperature for the onset of flash decreased with the electric field and the lower bound temperature was the materials Debye temperature. The results does indicate that non-linear lattice vibrations instigate flash.
Devinder Yadav, "Study of flash phenomena on single crystals of cubic 8 mol% yttria stabilized zirconia" in "Electric Field Enhanced Processing of Advanced Materials II: Complexities and Opportunities", Rishi Raj, University of Colorado, USA Olivier Guillon, Forschungzentrum Jülich, Germany Hidehiro Yoshida, National Institute for Materials Science, Japan Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/efe_advancedmaterials_ii/68