Field assisted and flash sintering of alumina and its relationship to conductivity and MgO-doping

We show that flash-sintering in MgO-doped alumina is accompanied by a sharp increase in electrical conductivity. Experiments that measure conductivity in fully dense specimens, prepared by conventional sintering, prove that this is not a cause-and-effect relationship, but instead that the concomitan...

Full description

Saved in:
Bibliographic Details
Published in:Journal of the European Ceramic Society 2011-12, Vol.31 (15), p.2827-2837
Main Authors: Cologna, Marco, Francis, John S.C., Raj, Rishi
Format: Article
Language:English
Subjects:
Al 2O 3
Aluminum oxide
Charging
Conductivity
Electrical resistivity
FAST
Flash-sintering
Mathematical analysis
Resistance sintering
Resistivity
Sintering
SPS
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We show that flash-sintering in MgO-doped alumina is accompanied by a sharp increase in electrical conductivity. Experiments that measure conductivity in fully dense specimens, prepared by conventional sintering, prove that this is not a cause-and-effect relationship, but instead that the concomitant increase in the sintering rate and the conductivity share a common mechanism. The underlying mechanism, however, is mystifying since electrical conductivity is controlled by the transport of the fastest moving charged species, while sintering, which requires molecular transport or chemical diffusion, is limited by the slow moving charged species. Joule heating of the specimen during flash sintering cannot account for the anomalously high sintering rates. The sintering behavior of MgO-doped alumina is compared to that of nominally pure-alumina: the differences provide insight into the underlying mechanism for flash-sintering. We show that the pre-exponential in the Arrhenius equation for conductivity is enhanced in the non-linear regime, while the activation energy remains unchanged. The nucleation of Frenkel pairs is proposed as a mechanism to explain the coupling between flash-sintering and the non-linear increase in the conductivity.
ISSN:0955-2219
1873-619X
DOI:10.1016/j.jeurceramsoc.2011.07.004