Correlation between structure, surface defect chemistry and 18O/16O exchange for La2Mo2O9 and La2(MoO4)3

The La2Mo2O9 and La-2(MoO4)(3) 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 x 10(-11) atm at 30 degrees C and 600 degrees C, and under an oxygen atmosphere at 2 x 10(-3) atm at 600 degrees C and 825 degrees C. High resolution spectra for La 3d, Mo 3d and O 1s states were obtained and analyzed. The kinetics of oxygen exchange were considered in the framework of a two-step model including the consecutive steps of dissociative adsorption and the incorporation of oxygen. The oxygen adsorption (r(a)) and incorporation (r(i)) rates were calculated. Correlations between the oxide surface defect chemistry and the rates of individual oxygen-exchange steps were discussed.

Automated summary

La2Mo2O9 and La-2(MoO4)(3) powders were synthesized using a solid-state reaction method and used to prepare dense ceramics. X-ray photoelectron spectroscopy was utilized to study the chemical composition and charge numbers of elements in the subsurface of lanthanum molybdates. The kinetics of oxygen exchange were analyzed in a two-step model, calculating the rates of oxygen adsorption and incorporation, and discussing correlations with oxide surface defect chemistry.