XPS/FTIR study of the interaction between NO and YBa2Cu3O7

Abstract

The combination of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and simultaneous thermal analysis (STA) studies has shown that the interaction between NO and YBa2Cu3O7 occurs at room temperature and above, resulting in the formation of the nitride, nitrate, nitrite (NO2 -), and nitrito (-ONO) groups, as well as in the release of N2, NO2, and N2O. The nitride species are observed at temperatures between 300 and 540 K but not at higher temperatures. The nitrate ion is the predominant nitrogen-containing species at temperatures below 540 K, and its concentration decays at elevated temperatures (>820 K). The nitrito group can be found at room temperature as well as elevated temperatures. The nitrite ion is observed with relatively low concentration at lower temperatures but becomes the predominant nitrogen-containing species at high temperatures. The maximum increase in the sample weight (∼7%) as measured by thermogravimetry (TG) corresponds to a net uptake of a NO2 group (or an NO molecule plus an O atom) per unit cell of YBa2Cu3O7. The NO interaction also results in the oxidation of a small portion (