Electrical transport in ultrafine ceramics: Effects of grain size-dependent solute segregation and nonstoichiometry
- Massachusetts Institute of Technology, Cambridge, MA (United States)
The interrelationship between microstructure, interfacial segregation, and electrical conductivity in fine-grained ceramics is discussed using recent examples from semiconducting and ionically-conducting systems. For polycrystals in which the ratio of impurity concentration/grain size is sufficiently low, the grain boundary excess of impurities and solutes is grain size dependent. This causes the specific grain boundary impedance to be a function of grain size in polycrystalline zirconia and ceria. At sufficiently fine grain sizes, i.e. in nanocrystals, interfacial defect thermodynamics can dominate the transport properties of the whole. Size reduction into the several-nanometer regime causes a reduction in the observed heat of reduction of CeO{sub 2-x} by over 2.4 eV per oxygen vacancy, and a correspondingly large increase in the electronic conductivity. This is attributed to preferential reduction at grain boundary atomic sites. Ultrafine-grained oxides may therefore be considered to be interface-doped materials.
- OSTI ID:
- 520409
- Report Number(s):
- CONF-960367-; TRN: 97:003394-0005
- Resource Relation:
- Conference: Workshop on mass and charge transport in ceramics, Nagoya (Japan), 15-16 Mar 1996; Other Information: PBD: 1996; Related Information: Is Part Of Ceramic transactions: Mass and charge transport in ceramics. Volume 71; Koumoto, Kunihito; Sheppard, L.M.; Matsubara, Hideaki [eds.]; PB: 643 p.
- Country of Publication:
- United States
- Language:
- English
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