Nanostructure, nanochemistry and grain boundary conductivity of yttria-doped zirconia

Alin Rizea ,  Jean-Marc Raulot ,  Claude Petot ,  Georgette Petot-Ervas ,  Gianguido Baldinozzi 

Ecole Centrale Paris, SPMS, UMR CNRS-ECP (ECP), Grande voie des vignes, Chatenay-Malabry 92295, France

Abstract

This work is aimed to a comprehensive study of the role of the microstructure and of the local chemistry at the grain-boundaries on the ionic grain-boundary conductivity in yttria (9mol%)-stabilized zirconia (YSZ) and in YSZ-alumina composites. Electrical conductivity measurements show that the grain-boundary conductivity (σgb) increases with the cooling rate at the end of sintering, when the grain size and the amount of Si in the ceramic decreases. Alumina additions lead to a decrease of σgb in the samples containing 1.0 wt% SiO2, while σgb passes through a maximum for heavier silicon contents. These results, coupled to TEM X-ray microanalysis, suggest that alumina nanoparticles interact strongly with SiO2 at the grain boundaries giving rise to a competitive effect: whereas the alumina nanoparticles increase the insulating character, they also reduce the vitreous phase at the grain boundaries, increasing the conductivity. Moreover, XPS analyses show that Si and Y segregate near the interfaces, on a depth smaller than 600nm. These analyses suggest a kinetic demixing process and they allow to explain the positive effect of a faster cooling rate at the end of sintering, responsible for the smaller amount of Si rejected at the grain-boundaries.


 

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Presentation: poster at E-MRS Fall Meeting 2004, Symposium G, by Gianguido Baldinozzi
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 18:56
Revised:   2009-06-08 12:55