Correlation between structure, surface defect chemistry and O/O exchange for LaMoO and La(MoO).

The LaMoO and La(MoO) powders were synthesized using a solid-state reaction method and used to prepare dense ceramics. X-ray photoelectron spectroscopy was used to study the chemical composition and charge numbers of the elements in the subsurface area of dense ceramics of lanthanum molybdates. The spectra were measured under an ultra-high vacuum of 7 × 10 atm at 30 °C and 600 °C, and under an oxygen atmosphere at 2 × 10 atm at 600 °C and 825 °C.

Oxygen surface exchange and diffusion in mayenite single crystal.

Oxygen surface exchange and diffusion in CaAlO single crystal were studied by a unique in situ method based on isotope equilibration in the gas phase. Although the interphase exchange rate and oxygen diffusion coefficient demonstrate good agreement with available data, only the employed method is efficient to isolate the contributions of various types of exchange; thus, for the first time, it is possible to estimate the surface heterogeneity of mayenite. The obtained results disprove conclusions previously developed in the literature; the temperature region of 750 °C to 850 °C is not the intermediate region where two types of oxygen diffusion coexist.