Effects of space charge, grain-boundary segregation, and mobility differences between grain boundary and bulk on the conductivity of polycrystalline Al/sub 2/O/sub 3/

Journal Article · Sat Mar 01 00:00:00 EST 1980 · J. Am. Ceram. Soc.; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1980.tb10688.x· OSTI ID:5407930

Tiku, S K; Kroeger, F A

The potential difference between grain boundary and bulk and the concentrations of native and foreign point defects in the bulk, the grain boundary (gb), and the subgrain boundary space-charge region (sg) of polycrystalline Al/sub 2/O/sub 3/ doped with acceptors are computed for the case that the dopants segregate at the grain boundaries, with either the ionized or the nonionized acceptor as the dominant species. Expressions are derived for the effective dc conductivity of a polycrystalline material on the basis of a model in which the grain has one or two shells with conductivities different from that of the bulk. Combination of the two results yields expressions for the effective ionic and electronic conductivity of doped Al/sub 2/O/sub 3/ as a function of grain size with distribution coefficients gb/sg, mobility ratios in the various regions, and equilibrium constants as parameters. At impurity concentrations normally found in ceramics, the contribution by subgrain boundaries to conductivity may be neglected. The theoretical results are compared to published data for Al/sub 2/O/sub 3/:Mg, Fe, and Ti.

• Research Organization: Univ. of Southern California, Los Angeles
• DOE Contract Number: EY-76-03-0113
• OSTI ID: 5407930
• Journal Information: J. Am. Ceram. Soc.; (United States), Vol. 63:3-4
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
ELECTRIC CONDUCTIVITY
GRAIN BOUNDARIES
DOPED MATERIALS
GRAIN SIZE
IMPURITIES
MOBILITY
POINT DEFECTS
SEGREGATION
SURFACES
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRICAL PROPERTIES
MATERIALS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SIZE
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360204 - Ceramics
Cermets
& Refractories- Physical Properties