Diffusion coefficients defect

The interpretation of the pre-factor as a conductivity as well as the correlation between defect diffusion coefficient Dk and mobility uk known as Nernst-Einstein equation follow directly from Table 3. 

Relationships Between Self-, Tracer, Chemical, Ambipolar, and Defect Diffusion Coefficients... 

There are various diflEiision coefficients (i) self-diflfusion coefficient, (ii) tracer diffusion coefficient, (iii) lattice diffusion coefficient, (iv) grain boundary diffusion coefficient, (v) surface diffusion coefficient, (vi) defect diffusion coefficients, and (vii) chemical, effective or interdiffusion coefficient. 

T is proportional to the square of the separation 2 a of the mosaic grain boundaries. If one of the two defect diffusion coefficients is much greater than the other, then only the smaller of the two remains in the denominator. The relaxation time is then inversely proportional to the diffusion coefficient of the slower defect. 

Goethem, van N Potter, de A. Bogaert, van den N. Dupret, F. (2008). Dynamic prediction of point defects in Czochralski silicon growth. An attempt to reconcile experimental defect diffusion coefficients with the criterion V/G. Journal of Physics and Chemistry of Solids, Vol. 69, No. 2-3, pp. 320-324, ISSN 0022-3697. 

The self-diffusion coefficient of iron is a direct proportion to the partial pressure of oxygen The defect diffusion coefficient is basically not related with the... 

The defect diffusion coefficient has basically nothing to do with the concentration of defects. Dy can be obtained via the following methods ... 

Determination of the defect diffusion coefficient (Dk) according to Eq. (6.42) requires knowledge of the defect concentration (ck). As can be seen from the above relationships, the temperature dependence of Dq2- is given by the temperature dependence of (7o2- and, in contrast to Dk and Uk, the enthalpy of defect formation is also included. 

If the two migrating defects are also the majority charge carriers, the concentration terms in Eq. (6.54d) disappear. If their charge numbers are also identical, the result is very simple and clear D is then the harmonic mean of the two defect diffusion coefficients. 

We can see from Eq. (6.54e) that lies between Dh /e and Dojvv - Since the first is generally the largest, this means that the electronic influence on the ambipolar diffusion is an accelerating one, and that the ionic influence acts as a brake. You can see that both diffusion coefficients and, in particular, the ionic defect diffusion coefficient must be sufficiently large in order to produce a high D. The lower value = Dof /Vg is — as demonstrated above — foimd for the case of an electron-rich electronic conductor. 

As the defect concentration in molybdenum disulfide is extremely low it is reasonable to assume that the defect diffusion coefficient, Dj, being the direct measure of defect mobility, is independent of their concentration and, consequently, the self-diffusion coefficient of sulfide ions, which is the product of Dj and [S ], must depend on sulfur pressure in the same way as the concentration of defects ... 

Thus, in the case of pure molybdenum sulfidation, eliminating the equilibrium constant iTfrom Eq. (20.5) and considering the fact that the defect diffusion coefficient, Dj, is the following function of temperature ... 

Adsorption Kinetics. In zeoHte adsorption processes the adsorbates migrate into the zeoHte crystals. First, transport must occur between crystals contained in a compact or peUet, and second, diffusion must occur within the crystals. Diffusion coefficients are measured by various methods, including the measurement of adsorption rates and the deterniination of jump times as derived from nmr results. Factors affecting kinetics and diffusion include channel geometry and dimensions molecular size, shape, and polarity zeoHte cation distribution and charge temperature adsorbate concentration impurity molecules and crystal-surface defects. 

Diffusion of the molecular gases can be compHcated by reactions with the glass network, especially at the sites of stmctural defects. The diffusion coefficient of water, for example, shows a distinct break around 550°C (110). Above 550°C, the activation energy is approximately 80 kj /mol (19 kcal/mol), but below 550°C, it is only 40 kJ/mol (9.5 kcal/mol). Proposed explanations for the difference cite the fact that the reaction between water and the sihca network to form hydroxyls is not in equiUbrium at the lower temperatures. 

This formula for ki can be cast into another form by using equations 1.169 and 1.170. We note first that in these latter equations K is the concentration of defects in CujO at 1 atm pressure of oxygen, so that (A ),Q) is the self-diffusion coefficient of Cu in CujO at this oxygen pressure. Call this self-diffusion coefficient Z7 , then... 

Therefore, the detailed analysis of concentration of defects in surface-adjacent layer and in the volume of adsorbent as well as assessment of the values of diffusion coefficients of defects and particles of various gases in material of adsorbent are very important for understanding the processes of both reversible and irreversible change in electrophysical characteristics of semiconductor during low temperature (if compared to the temperature of creation of defects) interaction with gaseous phase. 

For Schottky defects in an ionic crystal with a cubic lattice, the diffusion coefficient is given by the relationship, e.g. for a cation,... 

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