Research of the properties of a complex oxide Bi2Co1/3Cu1/3Ni1/3Nb2O9+Δ with a pyrochlore structure

Bismuth-containing monodoped pyrochlores have promising photocatalytic and dielectric properties. The paper presents the results of studying the properties of multielement pyrochlore containing transition 3d-elements in equivalent amounts. Mixed oxide pyrochlore of the composition Bi 2 Co 1/3 Cu 1/3 Ni 1/3 Nb 2 O 9+ Δ (sp. gr. Fd-3m, a = 10.5378 ± 6 Å) was synthesized by the solid-phase reaction method. The chemical state of transition element cations in the oxide pyrochlore was estimated by X-ray photoelectron spectroscopy (XPS). The parameters of the Bi5d, Nb3d, Co2p, Ni2p, Cu2p XPS spectra for the mixed pyrochlore were compared with the parameters of transition element oxides. The content of Cu (I, II) cations was determined based on the analysis of the relative intensity of peaks in the Cu2p spectrum. It has been established that for complex pyrochlore a characteristic shift of Bi4f- and Nb3d-spectra to the region of lower energies by 0.25 and 0.65 eV, respectively, is observed. The width of the forbidden band of pyrochlore for the direct allowed most intense electronic transition is 1.1 eV. The obtained results can be used to improve the technology of manufacturing multilayer ceramic capacitors and microwave dielectric materials.