Doping, Nonstoichiometry, and Conductivity

Oxygen ion vacancy concentrations can be increased by partial substitution of the tetravalent B-site ions with lower-valency cations, as shown in Eq. (8.3)  

Mb is a divalent cation, and Vq is an induced oxygen ion vacancy. It is expected that these additional vacant sites facilitate oxygen transport through the crystal by increasing the number of potential carriers. 

The p-type behavior of the undoped sample at high P02 has various possible explanations, the most likely being simply that equilibrium intrinsic oxygen 

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