Paramagnetic defects and impurities in pure ZnO ceramic powder and in ZnO ceramic powder doped with 0.5mol%Bi2O3 were investigated by means of the EPR spectroscopy. Single positive oxygen vacancies Vo+, several zinc vacancies, and Mn2+ impurities were detectable in the pure ZnO ceramic sample. Heat treatments in pre-vacuum and air revealed only an influence upon the signals of the zinc vacancies. Effects of reduction and oxidation after the heat treatments in pre-vacuum and air were, however, demonstrated by the EPR signal of the Vo+ centre in the ZnO ceramic sample doped with Bi2O3.

Investigation of the Oxygen Vacancy Balance in ZnO Ceramics by Means of EPR. Völkel, G., Pöppl, A., Voigtsberger, B.: Physica Status Solidi A, 1988, 109[1], 295-9