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Extension of Darken's Equation to Binary Diffusion in Ceramics
Author(s) -
COOPER ALFRED R.,
HEASLEY JAMES H.
Publication year - 1966
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1966.tb13258.x
Subject(s) - diffusion , binary number , relaxation (psychology) , thermodynamics , ceramic , ion , volume (thermodynamics) , extension (predicate logic) , flux (metallurgy) , electrical resistivity and conductivity , chemistry , materials science , chemical physics , physics , mathematics , organic chemistry , psychology , social psychology , arithmetic , quantum mechanics , computer science , programming language
The idea of a “relaxation velocity” to compensate for the differing mobilities of the species has been useful in describing binary diffusion in gases, nonelectrolyte liquids, and metals. The application of the idea to binary ceramic systems, particularly those with a common anion, is considered. By making certain simplifying assumptions, (1) the volume of a ceramic is primarily determined by the volume of the anion and (2) the chemical potential of the anion does not depend on cation ratio as long as electrical neutrality is preserved, it is possible to arrive at the appropriate expression for the binary diffusion coefficients in terms of the self‐diffusion coefficients and valencies of all species and the activity of one of the compounds. This result is analyzed by considering the intrinsic flux densities of the species, the concentration distribution, and the relaxation velocity and marker movement for several cases and these are plotted schematically.