Diffusion and surface exchange coefficients

For predominant electronic conductors like, for example, the perovskites Lai xSrxCoi.yFey03 is determined by the ratio of the oxygen self diffusivity and surface exchange coefficient. Both parameters can be measured simultaneously by using isotopic exchange techniques. Calculations show that... 

In order to gain a direct measurement of the oxide ion diffusion and surface exchange coefficients in ceramic materials an isotopic exchange and SIMS analysis technique has to be used. This technique is detailed elsewhere [9] and has been successfully used for a number of SOFC component materials, most notably with electrolytes [10,11] and cathodes... 

Kim, S., Yang, Y.L., Jacobson, A.J. and Abeles, B. (1998) Diffusion and surface exchange coefficients in mixed ionic electronic conducting oxides from the pressure dependence of oxygen permeation. Solid State Ionics, 106 (3-4), 189-195. 

Table 8.1 Oxygen diffusion and surface exchange coefficients for various materiais determined by the lEDP technique.

Taking into account the three different potentials, buik> Es,f> and s.p> the diffusion and surface exchange coefficients can be measured using the following expressions ... 

Table 14-3 Compilation of O2 and H2 diffusion and surface exchange coefficients in perovskites and perovskite membrane.

Diffusion and Surface Exchange Coefficients Structure-Property Correlations... 

Table 14.3 compiles a selection of published results on O2 dififusion and surface exchange coefficients in perovskites and perovskite membranes. The last two rows of the table include H2 diffusion and surface exchange coefficients. As can be inferred from Table 14.3, the vacancy diffusion in perovskites falls into the range of 2 X 10 -2 x 10 m /s, whereas the surface exchange coefficients show a broad variety of values depending on the perovskite composition and on the presence of secondary phases. 

Fielitz, P. and Borchardt, G. (2001) On the accurate measurement of oxygen self-diffusivities and surface exchange coefficients in oxides via SIMS depth profiling. Solid State Ionics, 144,... 

Chater, R.J., Carter, S., Kilner, J.A., and Steele, B.C.H. Development of a novel SIMS technique for oxygen self-diffusion and surface exchange coefficient measurements in oxides of high diffusivity. Solid State Ion. 1992, 53,... 

S. Diethelm, A. Closset, J. Van Herle, K. Nisancioglu, Determination of chemical diffusion and surface exchange coefficients of oxygen by electrochemical impedance spectroscopy, J. Electrochem. Soc., 2002,149,11, pp. E424-E432. 

Electrical conductivity relaxation (ECR) method. ECR method is rather simple, it does not require expensive equipment and provides high precision in determination of the oxygen chemical diffusion and surface exchange coefficients in mixed ionic-electronic conductors [64-66],... 

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