Grain boundary conductivity of yttria-doped zirconia: Influence of the microstructure and composite effect |
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Authors: | A Rizea M Filal D Chirlesan F Lacour-Laher C Petot G Petot-Ervas |
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Institution: | (1) Ecole Centrale de Paris, CNRS-SPMS, Grande voie des Vignes, F-92295 Chatenay Malabry, France |
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Abstract: | Electrical conductivity measurements have been performed on yttrium-doped zirconia and on YSZ-alumina composites sintered
from powders prepared by conventional techniques (commercial powder) or by freeze-drying. The results have been analyzed taking
into account the microstructure of the interfaces which were characterized by electron microscopy. The samples sintered from
freeze-dried powders show the highest conductivity values and this conductivity decreases in the presence of alumina. The
microstructure of these polycrystals is clean, homogeneous with lens-shaped glassy pockets at triple-points and there is no
evidence for continuous boundary films. Contrary, the samples prepared and sintered from commercial powders show a poor microstructure
and the presence of a glassy film in a large number of grain boundaries. Furthermore, alumina leads to an increase in conductivity,
which reaches a maximum at around 2 mol-% alumina. This result may be attributed to the influence of alumina on the viscosity
and wetability of the glassy phase. However, all samples show the same grain boundary activation energy. This confirms that
the transport mechanism is the same in all cases and that only clean grain boundaries contribute to the transport processes.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. |
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