Atomic absorption photometry of excess Zn in ZnO



Zn excess in ZnO is built up automatically at high temperatures. Excess Zn in hydrothermally grown ZnO single crystals were investigated by the atomic absorption photometry (AAP) method. To determine the excess zinc in ZnO samples, the AAP of zinc vapour was used in the conditions of solid-vapour equilibrium. Zn AAP allowes to eliminate excess Zn connected differentially in ZnO samples. To fix Zn non-stoichiometry, all the ZnO samples tested were previously heat treated at temperature interval from 850 to 900 °C and at fixed Zn vapour pressures from 0.1 to 0.9 of saturated zinc vapour pressure at given treatment temperature. The analysis of temperature dependence of zinc vapour pressure indicated that the impurity metals take active role in the determination of non-stoichiometric zinc. The impurities Mn, Fe, Co, Ni and Cu form oxides which will reduce during annealing in Zn vapor up to metals form. During AAP measurement in optical cuvette, these metals react with ZnO and give additional Zn vapor pressure. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)