Synthesis and Characterization of Ca and Ba Doped LAMOX Materials and Surface Study by X-ray Photoelectron Spectroscopy

摘要

(La_(1-x)Ca_x)2Mo2O_(9-δ) and (La_(1-x)Ba_x)2Mo2O_(9-δ) (x = 0.05, 0.1, 0.15, 0.2) materials were prepared at 800 °C by co-precipitation method and characterized by X-ray diffraction and scanning electron microscope. The XRD diagrams showed the presence of CaMoO4 and BaMoO4 secondary phases only at high contents of the dopants. X-ray photoelectron spectroscopy was used to study the surface chemical structure of doped and undoped materials (La2Mo2O9). It was found that the La and Mo atoms had 3+ and 6+ valence states, respectively. The absence of carbides and carbonates at surface suggests that, the unavoidable carbon contamination did not interact with the metal atoms, which allows applications using carbonaceous fuels, and, that the formation of secondary phases did not influence the surface state. XPS spectra show that the covalent character of the La-0 bond was enhanced with calcium doping as compared to barium, predicting interesting conductive and catalytic properties of the materials.