Effects of preparation method and temperature on the cation distribution of ZnGa2O4 spinel studied by X-ray photoelectron spectroscopy

ZnGa2O4 spinel powders were prepared by two different methods: sol-gel method (SG) and solid state reaction method (SSR). The distribution of cations (Ga3+, Zn2+) in the tetrahedral and octahedral sites in ZnGa2O4 as a function of synthesis method and annealing temperature has been investigated by X-ray photoelectron spectroscopy. The results showed that Ga3+ ions were located in large proportions in the octahedral sites and in small proportions in the tetrahedral sites in all the ZnGa2O4 powders. The inversion parameter (2 times the fraction of Ga3+ ions in tetrahedral sites) decreased with increasing annealing temperature. The samples prepared by SSR method showed lower inversion degree when compared with those by SG method. The change of Zn2+ fraction in octahedral sites is consistent with that of inversion parameter. Analysis of the emission properties indicated that Ga3+ ions occupied two coordination sites in the samples and changed with temperature.