PREPARATION AND STRUCTURAL INVESTIGATIONS OF THE MIXED BISMUTH NIOBATES, CONTAINING TRANSITION METALS

Mixed bismuth niobium oxides, containing transition metals were synthesized by using solid-state reactions in the systems Bi2O3-Nb2O5-MO(M2O3), M-Cr, Mn, Fe, Co, Cu. Powder X-ray diffraction studies of these compounds show, that crystal phases with structures as the orthorhombic BiNbO4, the layer perovskite-like and the pyrochlore-type ones can be formed depending on the metal oxides molar ratio and the conditions of the synthesis. It was found out that the pyrochlore-type crystal structure(Fd3m) is stable for these compounds. The lattice parameters were calculated. The structural determinations by Rietveld full-profile technique were carried out on powdered samples with pyrochlore-type structure. The oxidation states of the metal cations were determined by the XPS method.