Investigation of the oxygen vacancy balance in ZnO ceramics by means of EPR

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