NO adsorption on a single crystal and a polycrystalline powder of LiNbO₃

Abstract

NO has been adsorbed as NO₂⁻ and NO₃⁻ on an LiNbO₃ single crystal at room temperature. NO⁻ was observed in the XPS spectrum for the N 1s level of the LiNbO₃ single crystal after exposure at 200 and 400 °C, respectively. An LiNbO₃ polycrystalline powder had only a peak from NO₃⁻ after exposure between room temperature and 400 °C. The oxygen vacancies of lattice oxygen were produced with both LiNbO₃ samples after exposure at room temperature. These oxygen vacancies in the LiNbO₃ single crystal were partially refilled with NO⁻ after exposure at 200 and 400 °C. On the other hand, the vacancies associated with the polycrystalline powder were partially refilled by the out-diffusion of oxygen ions from the bulk to the surface after exposure at 200 and 400 °C. The ions of lithium and oxygen in the bulk LiNbO₃ polycrystalline powder diffuse more easily to its surface than those present in the LiNbO₃ single crystal.