WEB Ionic to Mixed Electronic-Ionic Conductivity Transition During Flash SinteringWednesday (01.01.2020) 00:30 - 00:45 Part of:
Flash sintering is accompanied by a significant change in the electrical conductivity of ceramics which are pure ionic conductors and even insulators. In this presentation, we explore the nature of the transition and ask the question whether the mechanism changes from ionic to mixed electronic-ionic conduction. The experiments are done on single crystals of cubic zirconia. We sought quantitative measurements of the mixed behavior in the form of the transport number for electronic conduction (that is, the ratio of the electronic conductivity divided by the total conductivity). Two types of experiments were conducted: (a) in-situ impedance spectroscopy, and (b) live measurements of conduction where the oxygen is transported into a closed chamber, and it is measured as a function of time by the change in pressure within the cell, by means of a reference electrode.
The impedance spectroscopy measurement showed a definite transition to electronic conduction (which, incidentally, initiates well before the cusp of the flash transition). The total conductivity was measured. However, the transport number could be estimated only with the assumption that the ionic conductivity, which was determined without the flash, remains unchanged during the flash. The “fuel cell” type measurements, however, are providing full information about the total conductivity and the ionic conductivity. Preliminary results suggest that ionic conductivity is significantly affected by the flash. Thus, the transport number measured during the cell experiment appears to be higher than measured by the in-situ impedance spectroscopy method.
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