Diffusion in Materials with Ionic and Electronic Disorder

1990 ◽  
Vol 210 ◽  
Author(s):  
Joachim Maier
Keyword(s):  
Ionic Conduction ◽  
Diffusion Theory ◽  
Local Equilibrium ◽  
Transport Coefficients ◽  
Electrochemical Techniques ◽  
Chemical Diffusion ◽  
Tracer Diffusion ◽  
Internal Defect ◽  
Concentration Cell ◽  
The Individual

AbstractBesides some necessary reviewing of conventional diffusion theory, this paper deals with the modification of the mass and charge transport equations originating from the occurence of internal defect-chemical reactions (especially valence changes of the defects) which can be considered to be in local equilibrium. It is shown how the phenomenological transport coefficients for chemical diffusion, tracer diffusion and ionic conduction depend on the individual defect diffusivities under such general conditions. Moreover, the evaluation formulae of well-known electrochemical techniques such as Wagner-Hebb polarization and concentration cell experiments have to be modified. Application is made to the influence of trapping effects in doped SrTi03, to the valence changes in YBa2Cu3O6+x as well as to the mixed conduction in orthorhombic PbO.

Local Equilibrium Evaluation of Thermal Transport Coefficients in Simple Liquids

1968 ◽  
Vol 48 (2) ◽  
pp. 951-953 ◽  
Author(s):  
J. Misguich ◽  
G. Nicolis ◽  
J. A. Palyvos ◽  
H. Ted Davis
Keyword(s):  
Thermal Transport ◽  
Local Equilibrium ◽  
Transport Coefficients ◽  
Simple Liquids

scholarly journals Interdiffusion Data in Multicomponent Alloys as a Source of Quantitative Fundamental Diffusion Information

2007 ◽  
Vol 263 ◽  
pp. 1-10 ◽  
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Diffusion Processes ◽  
Chemical Diffusion ◽  
Tracer Diffusion ◽  
Ternary Alloys ◽  
Diffusion Data ◽  
Fundamental Information ◽  
Random Alloy ◽  
Phenomenological Coefficients ◽  
Correlation Factors ◽  
Alloy Systems

Tracer diffusion experiments have historically furnished much of the information about fundamental diffusion processes as embodied in such quantities as tracer correlation factors and vacancy-atom exchange frequencies. As tracer diffusion experiments using radiotracers are rather less often performed nowadays, it is important to be able to process other diffusion data to provide similar fundamental information. New procedures that are primarily based around the random alloy model have been established recently for analyzing chemical diffusion data in binary and ternary alloy systems. These procedures are reviewed here. First, we review the random alloy model, the Sum-rule relating the phenomenological coefficients and three diffusion kinetics formalisms making use of the random alloy. Next, we show how atom-vacancy exchange frequency ratios and then component tracer correlation factors can be extracted from chemical diffusion data in alloy systems. Examples are taken from intrinsic diffusion and interdiffusion data in a number of binary and ternary alloys.

A Chemical Bonding Approach to Ionic Conduction and Thermal Expansion in Oxide Ion Conductors

2010 ◽  
Vol 72 ◽  
pp. 343-347 ◽  
Author(s):  
Sachi Taniguchi ◽  
Masaru Aniya
Keyword(s):  
Thermal Expansion ◽  
Ionic Conductivity ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Ionic Conduction ◽  
Point Of View ◽  
Semiempirical Methods ◽  
Oxygen Ionic Conductivity ◽  
The Difference ◽  
The Individual

In complex perovskite-type oxides which have been studied as cathode materials, the thermal expansion coefficient increases with the increase in the oxygen ionic conductivity. In the present study, with the aim to explain such a behavior, a research has been carried out from a chemical bond point of view. For oxides A1-xA′xB1-yB′yO with perovskite structure, the ionicity of the individual bond, A-O and B-O, and the thermal expansion coefficient of mixed compounds were estimated by using semiempirical methods. It has been shown that the thermal expansion coefficient and the oxygen ionic conductivity decrease with the increase in the difference of the ionicity between A-O and B-O bonds. It is also found that the tolerance factor and the specific free volume are linearly correlated with the difference of ionicity.

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