State of Chromium in Solid Solutions of Multicomponent Bismuth Niobates with Pyrochlore Structure

Abstract Two series of iron-containing solid solutions Bi2Mg1− x Fe x Nb2O9+δ and Bi2MgNb2−2 x Fe2 x O9−δ of pyrochlore structure were obtained by the traditional solid phase synthesis method. The electronic state and character of exchange interactions of iron atoms in solid solutions were investigated by methods of magnetic dilution and NEXAFS-spectroscopy. According to X-ray spectroscopy and magnetic susceptibility data, iron(III) atoms are distributed mainly in octahedral positions of niobium(V) and in a dominant amount are in the charge state of Fe(III) in the form of monomers and exchange-bonded clusters mainly with antiferromagnetic type of exchange. Differences in magnetic behavior of iron-containing solid solutions of both series have been revealed. Antiferromagnetic and ferromagnetic exchange can be realized between iron atoms, which, with increasing concentration of paramagnetic atoms and averaging structure distortions, becomes less significant. The parameters of exchange interactions in clusters and distribution of iron paramagnetic atoms depending on the concentration of solid solutions have been calculated.

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Spectral studies of bismuth-containing pyrochlores

Journal of Physics Conference Series ◽

10.1088/1742-6596/2103/1/012146 ◽

2021 ◽

Vol 2103 (1) ◽

pp. 012146

Author(s):

S V Nekipelov ◽

N A Zhuk ◽

O V Petrova ◽

D V Sivkov ◽

K A Bakina ◽

...

Keyword(s):

Charge State ◽

Solid Solutions ◽

Pyrochlore Structure ◽

Spectral Studies ◽

Nexafs Spectroscopy ◽

Cobalt Nickel ◽

Metal Atoms ◽

Thermal Stable

Abstract Thermal stable solid solutions of titanates, niobates, and tantalates of bismuth with a pyrochlore structure doped with 3d-metal atoms were studied using XPS and NEXAFS spectroscopy. Based on spectral studies, it was shown that the manganese, cobalt, nickel and copper atoms in these solid solutions have mainly charge state +2 and iron atoms – charge state +3.

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Structural determination of new solid solutions [Y2-xMx][Sn2-xMx]o7-3x/2 (M = Mg or Zn) by Rietveld method

Processing and Application of Ceramics ◽

10.2298/pac1004237d ◽

2010 ◽

Vol 4 (4) ◽

pp. 237-243 ◽

Cited By ~ 2

Author(s):

Mohamed Douma ◽

Hossain El ◽

Raquel Trujillano ◽

Vicente Rives

Keyword(s):

Solid Solutions ◽

Rietveld Method ◽

Structural Parameters ◽

Pyrochlore Structure ◽

Solid State Reaction Method ◽

Lattice Parameter ◽

X Ray Diffraction ◽

Pyrochlore Type ◽

Ft Ir

New [Y2-xMx][Sn2-xMx]O7-3x/2 (0 ?x? 0.30 for M = Mg and 0 ?x? 0.36 for M = Zn) solid solutions with the pyrochlore structure were synthesized via high-temperature solid-state reaction method. Powder X-ray diffraction (PXRD) patterns and Fourier transform infrared (FT-IR) spectra showed that these materials are new non-stoichiometric solid solutions with the pyrochlore type structure. The structural parameters for the solids obtained were successfully determined by Rietveld refinement based on the analysis of the PXRD diagrams. Lattice parameter (a) of these solid solutions decreases when x increases in both series. All samples obtained have the pyrochlore structure Fd-3m, no. 227 (origin at center -3m) with M2+ (M = Mg2+ or Zn2+) cations in Y3+ and Sn4+ sites, thus creating vacancies in the anionic sublattice.

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