Theoretical calculations were presented for equilibrium concentrations of zinc and oxygen vacancies in ZnO. Results were presented at the sintering temperature, and also at room temperature. Theoretical calculations of reaction constants showed that the intrinsic donor was the oxygen vacancy, rather than the zinc interstitial. The depletion of vacancies in the surface region, as the ZnO was cooled from the sintering temperature, was also calculated. Homojunction effects which were caused by such depletion were shown to be small.

Intrinsic Defects in ZnO Varistors. Mahan, G.D.: Journal of Applied Physics, 1983, 54[7], 3825