It was recalled that recent work dealing with O self-diffusion in ZnO had shown that O diffusion took place by means of doubly negatively ionized interstitial O. This O diffusion mechanism was reviewed and, based upon experimental data for the O self-diffusion and electrical conductivity of Al-doped and undoped ZnO, it was suggested that O self-diffusion took place by means of an interstitial mechanism; but with the interstitial O having a null or a single negative effective charge.

About the Oxygen Diffusion Mechanism in ZnO. A.C.S.Sabioni: Solid State Ionics, 2004, 170[1-2], 145-8