International Conference Physics.SPb/2025
Spectroscopy of condensed matter

XPS, NEXAFS characterization of Cu–Co codoped bismuth tantalate with pyrochlore structure

K. N. Parshukova^a, S. V. Nekipelov^b, A. V. Koroleva^c, B. A. Makeev^d, A. M. Lebedev^e, R. I. Korolev^a, N. A. Zhuk<sup>a

a</sup> Syktyvkar State University
^b Institute of Physics and Mathematics, Komi Science Centre, UrB RAS
^c Saint Petersburg State University
^d Geology Institute of Komi Scientific Center, Ural Branch of the Russian Academy of Sciences
^e National Research Centre "Kurchatov Institute", Moscow

Abstract: The chemical state of metal cations in pyrochlore Bi$_2$Cu$_{1/2}$Co$_{1/2}$Ta$_2$O$_{9\pm\delta}$ (sp. gr. Fd-3m, $a$ = 10.5379(8) $\mathring{\mathrm{A}}$) was characterized using XPS and NEXAFS spectroscopy. Based on the shift of the XPS Ta4$f$ spectrum toward lower energies by 0.9 eV, the effective charge of tantalum cations was established to be +(5-$\delta$). The NEXAFS Cu2$p$ spectra of pyrochlore are a superposition of the spectra from Cu(I) and Cu(II) cations. According to the analysis of the relative intensity of peaks in the XPS Cu2$p$ spectrum, the Cu(I)/Cu(II) ratio is 9/11. The nature of the NEXAFS and XPS Co2$p$ spectra indicates a Co(II, III) state.

Keywords: pyrochlore, NEXAFS, XPS, 3$d$ elements, ion charge state.

Received: 03.05.2025
Revised: 12.07.2025
Accepted: 24.10.2025

DOI: 10.61011/OS.2025.10.61937.7972-25