Internal Reduction in Nonmetallic Solutions

From Eqn. (9.16), we see that the metal A is precipitated within the rigid, dense-packed oxygen ion sublattice of the oxide matrix. The local volume at the reaction front is thus increased by the molar volume per mole of vacancies. Large strains and stresses are the immediate result. In contrast, if (A,B)304 is internally reduced to yield (A, B)0, the oxygen ion sublattice remains essentially undistorted, except for 

The quantitative discussion of internal reduction kinetics follows the discussion presented in the previous section on internal oxidation. The fundamental kinetic problem to be solved is again the calculation of the rate of advance of the reaction front (Fig. 9-6). To this end we note that 

Equation (9.17) balances the vacancy production and the amount of reduced, 

Nv( f) can be determined by the application of point defect thermodynamics at F, where the equilibrium defect concentrations are found from the following reaction 

The corresponding equilibrium condition (with aA = 1 for the activity of metallic A and 2- Ny - Nh ) reads 

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