Structural, optical and electrical study of new polycrystalline Bi1.5-xCexSb1.5CuO7 solid solution fractions with pyrochlore-type structure

Abstract

This study is a contribution to the development of novel materials based on transition multi metal oxides, which can be applied as photocatalysts or solid electrolytes in solid fuel cells. A new pyrochlore-like solid solution fractions with general chemical formula Bi1.5−xCexSb1.5CuO7 was synthetized and characterized using solid-state reaction and characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrical resistivity measurements and solid-state ultraviolet–visible spectroscopy (UV–Vis). The XRDP analysis revealed a high purity pyrochlore-like structure of the solid solution fractions, this being primary with cerium saturation between x=0.2. and x=0.4. A significant decrease of the refined cubic cell parameter was observed, in accordance with the size difference between bismuth and cerium cations. Also, a drastic drop off in electrical resistivity was observed at x=0.4. Besides, the core level X-ray photoelectron spectroscopy technique clearly detected the presence of all elements involved in the composition of these materials, and proved the simultaneous trivalent and tetravalent oxidation states of incorporated cerium. Furthermore, secondary and back-scattered electrons scanning electron microscopy analysis allowed the monitoring of the grain size as well as the phase inhomogeneity of the solid solution fractions. Finally, it was thus found that the optical band gap energy of the solid solution fractions was about 1.8 ​eV.