TY - JOUR

T1 - XPS study of pyrochlore type Bi2Cu1/3Ni1/3Co1/3M2O9±δ (M-Nb,Ta)

AU - Nekipelov, S.v.

AU - Petrova, О.v.

AU - Koroleva, A.v.

AU - Krzhizhanovskaya, M.G.

AU - Zhuk, N.a.

PY - 2024/11/21

Y1 - 2024/11/21

N2 - Mixed oxide cubic pyrochlores of the composition Bi2Cu1/3Ni1/3Co1/3(Nb/Ta)2O9±δ (sp.gr. Fd-3m) were synthesized for the first time by standard ceramic technology. According to X-ray phase analysis and Rietveld analysis, the Bi2Cu1/3Ni1/3Co1/3(Nb/Ta)2O9±δ samples are single-phase and have a cell parameter of 10.5416(3)/10.5341(2) Å, respectively. The chemical state of transition element cations in oxide pyrochlores was characterized by X-ray photoelectron spectroscopy (XPS). The Nb 3d and Ta 4f spectra of the synthesized pyrochlores exhibit a characteristic shift to lower energies by 0.65 eV, which indicates that the effective charge of the niobium and tantalum cations is +(5-δ). A shift of Bi 4f spectra by 0.25 eV is typical only for niobium pyrochlore. It has been shown that NEXAFS Cu 2p spectra of oxide ceramics, according to the main characteristics of the spectrum, represent a superposition of spectra from Cu(I) and Cu(II) cations. Based on the analysis of the relative intensity of the peaks in the XPS spectrum of Cu 2p for pyrochlores, the content of Cu(I,II) cations was estimated. The ratio of Cu(I) to Cu(II) cations in niobium pyrochlore is higher than in tantalum pyrochlore, with approximately two times more Cu(I) cations than Cu(II). X-ray spectroscopy studies indicates that Co and Ni cations are present in the valence state (II, III).

AB - Mixed oxide cubic pyrochlores of the composition Bi2Cu1/3Ni1/3Co1/3(Nb/Ta)2O9±δ (sp.gr. Fd-3m) were synthesized for the first time by standard ceramic technology. According to X-ray phase analysis and Rietveld analysis, the Bi2Cu1/3Ni1/3Co1/3(Nb/Ta)2O9±δ samples are single-phase and have a cell parameter of 10.5416(3)/10.5341(2) Å, respectively. The chemical state of transition element cations in oxide pyrochlores was characterized by X-ray photoelectron spectroscopy (XPS). The Nb 3d and Ta 4f spectra of the synthesized pyrochlores exhibit a characteristic shift to lower energies by 0.65 eV, which indicates that the effective charge of the niobium and tantalum cations is +(5-δ). A shift of Bi 4f spectra by 0.25 eV is typical only for niobium pyrochlore. It has been shown that NEXAFS Cu 2p spectra of oxide ceramics, according to the main characteristics of the spectrum, represent a superposition of spectra from Cu(I) and Cu(II) cations. Based on the analysis of the relative intensity of the peaks in the XPS spectrum of Cu 2p for pyrochlores, the content of Cu(I,II) cations was estimated. The ratio of Cu(I) to Cu(II) cations in niobium pyrochlore is higher than in tantalum pyrochlore, with approximately two times more Cu(I) cations than Cu(II). X-ray spectroscopy studies indicates that Co and Ni cations are present in the valence state (II, III).

UR - https://www.mendeley.com/catalogue/dcf647ca-14e7-37d9-87df-8f80a98fea20/

U2 - 10.1016/j.ceramint.2024.11.311

DO - 10.1016/j.ceramint.2024.11.311

M3 - Article

JO - Ceramics International

JF - Ceramics International

SN - 0272-8842

ER -