Zinc oxynitride powders examined by x-ray absorption near edge spectroscopy

Anti-bixbyite-type zinc oxynitride powders Zn3(N1-xOx)2-y could be prepared by directly nitriding zinc powder under ammonia gas flow. Zn3(N0.91O0.09)1.98 could be obtained after 168 hours of nitridation at 500 °C. X-ray absorption spectra near N and O K-edges for some zinc oxynitrides were recorded in both total electron yield and fluorescence modes. The two spectra provide complementary information on the near surface, and on what can be considered as the bulk of the powdered zinc oxynitride. O K-edge spectra clearly appeared for all the measured oxynitrides in both the total electron yield and fluorescence modes. However, only the N K-edge fluorescence yield spectrum was detected even for the nitrogen-richest oxynitride Zn3(N0.91O0.09)1.98. These results imply that the prepared zinc oxynitrides were covered with some ten nanometers of oxide layers and that nitridation of zinc powders would proceed by thinning down the oxide layers.