Zinc nonstoichiometry in ZnO

Excess Zn in powder and in ceramic ZnO is investigated by the atomic absorption photometry (AAP) method. All the ZnO samples tested were previously heat treated at temperature 900 °C and at fixed Zn pressures from 0.1 to 0.6 of saturated pZn at given treatment temperature. The vapour–crystal equilibrium in ZnO:Zn crystal was established in 20–40 min. To determine the excess zinc in ZnO samples, the AAP of zinc vapour was used in the conditions of solid–vapour equilibrium. Optical absorbance of zinc, proportional to the concentration of zinc atoms in the vapour phase, was registered photoelectrically on the Zn resonance line. The analysis of temperature dependence of zinc pressure indicated that the value of zinc excess lies in the concentration interval of 1018–1019 cm−3 and depends on the sample biography and the conditions of preliminary heat treatment. Zn adsorption on powder ZnO grain surfaces and the reactions of impurity metals with excess Zn in ZnO ceramics were observed in Zn AAP experiments.