Equilibrium between an oxide and oxygen the Wagner prevalent defect approximation

Equilibrium between an oxide and oxygen the Wagner prevalent defect approximation 

In the Wagner classification, such as we have estabhshed in section 2.3.2, zinc oxide is non-stoichiometric and has zinc ions in interstitial positions and free electrons. In the presence of oxygen, the oxide tends to approach stoichiometry  

There are two equations for this problem the law of mass action is applied to the preceding equilibrium, on the assunption that there are very diluted defects  

The resolution of this system of two equations leads to the ejq)ression of the concentration of the two defects according to oxygen pressure at a given temperature  

We can again consider the preceding assumption for equilibrium between atty Wagner oxide and a gas corresponding to the anion. We obtain laws of the same type as the preceding ones for the concentration of point defects or electric conductivity. 

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