Mixed Magnesium and Zinc Oxide Prepared by Co-precipitation and Analyzed by XPS

Two Zinc-Magnesium Oxide powders were prepared by means of a sol-gel method based on the mixing of nitrates of Mg and Zn, followed by complexation with citric acid. The samples are characterized by a nominal (i.e. calculated from the weighted amount of precursors) Zn/Mg atomic ratio of 0.01 (specimen 1, Accession #1232), and 0.5 (specimen 2, Accession #1233). The surface properties and the influence of the Zn/Mg atomic ratio are investigated by means of XPS (using a standard Al Kα). Besides the wide scan spectra, detailed spectra for the Mg 1s, Zn 2p3/2 and O 1s regions and related data are presented and discussed. XP analysis confirms the presence of Mg (II) and Zn (II). The XPS Zn/Mg atomic ratio is always lower than the nominal one; this is particularly evident in specimen 1 (Accession #1232) thus suggesting a certain surface segregation of magnesium. The O/(Mg + Zn) atomic ratio is higher than the nominal one and decreases with increasing the Zn/Mg atomic ratio (from 1.5 for [Zn/Mg]nom = 0.01 to 1.3 for [Zn/Mg]nom = 0.5).