Synthesis and Structural Study of Pb2Re2O7−xPyrochlores

Abakumov, Artem M.; Shpanchenko, Roman V.; Антипов, Е.В.; Kopnin, Evgeni; Capponi, J.J.; Marezio, M.; Lebedev, Oleg I.; Tendeloo, G. Van; Amelinckx, S.

doi:10.1006/jssc.1998.7778

Cited by 7 publications

(6 citation statements)

References 5 publications

(3 reference statements)

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“…The (Mn/Re)O 6 octahedron is nearly regular with a Mn/Re−O distance of 2.02 Å, reflecting the statistical distribution of Mn/Re atoms at the octahedral (16c) sites (Mn II /Re VI −O distance expected on the basis of average octahedral radii is 2.09 Å). The Pb−O coordination and Pb−O bond distances are similar to other defect pyrochlores containing Pb II . Moreover, a bond valence analysis of Pb in pyrochlore Pb 2 MnReO 6 gives a valence of +1.78.…”

Section: Resultssupporting

confidence: 70%

Perovskite and Pyrochlore Modifications of Pb₂MnReO₆: Synthesis, Structure, and Electronic Properties

et al. 2003

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We describe the synthesis and investigations of Pb 2 MnReO 6 in perovskite and pyrochlore modifications. Both the modifications are formed at atmospheric pressure, the perovskite (I) at 550°C and the pyrochlore (II) at 600°C. Rietveld refinements of the structures using the powder XRD data show that oxide I adopts the monoclinic (P2 1 /n) double perovskite structure with partial ordering (∼72%) of Mn II /Re VI at the octahedral sites, while oxide II crystallizes in a defect-pyrochlore structure where Mn II /Re VI are disordered at the octahedral sites. The frustrated cation sublattice precludes a long-range ordering of Mn/Re in the pyrochlore structure. I is a semiconductor showing evidence for a ferrimagnetic ordering at T c ∼ 100 K, but the small saturation magnetic moment (〈S〉 ) 0.81) and the divergence between FC and ZFC magnetization data are consistent with spin-glass-like behavior and a partially ordered Mn/Re in the double perovskite structure. On the other hand, both the Curie-Weiss paramagnetism down to ∼5 K and non-Arrhenius electrical resistivity behavior of II suggest a spin-liquid/spin-glass ground state that is consistent with the frustrated cation sublattice of the pyrochlore structure.

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Section: Resultssupporting

confidence: 70%

Perovskite and Pyrochlore Modifications of Pb₂MnReO₆: Synthesis, Structure, and Electronic Properties

et al. 2003

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“…There is a noticeable difference in the values of the B iso between the Pb and the Tc, this is due to the Biso for the 8-coordinate site in the pyrochlores being larger than that of the 6-coordinate site reflecting its more irregular environment. Interestingly the electron diffraction images of Pb 2 Re 2 O 7-d published by Abakumov and co-workers ( Abakumov et al, 1998 ) did not show any diffuse features characteristic of cation disorder suggesting there may be subtle differences between the Re and Tc oxides. Diffuse features have been observed in electron diffraction studies of numerous Bi containing pyrochlores including Bi 2 Ru 2 O 7 ( Goodwin et al, 2007 ).…”

Section: Resultsmentioning

confidence: 90%

“…There was no evidence for reflections of the type hk 0 with h + k = 2 n such as the 420 or 640 reflections in the diffraction patterns indicative of a lowering of symmetry from

as is observed for Pb 2 Ru 2 O 6.5 ( Beyerlein et al, 1984 ) and Pb 2 Ir 2 O 6.5 ( Kennedy, 1996 ). Evidently the structure of Pb 2 Tc 2 O 7-d , like that of Pb 2 Re 2 O 7-d ( Abakumov et al, 1998 ), is described by space group

and does not exhibit oxygen vacancy ordering.…”

Section: Resultsmentioning

confidence: 92%

“…Beyerlein and co-workers (Beyerlein et al, 1984) reported that the analogous lead-ruthenium pyrochlore is non-stoichiometric and displays oxygen vacancy ordering, the stoichiometry actually being Pb 2 Ru 2 O 6.5 and the resulting space group being F43m, rather than Fd3m as seen in Bi 2 Ru 2 O 7-d (Beyerlein et al, 1984;Facer et al, 1993;Avdeev et al, 2002). The iridium pyrochlore Pb 2 Ir 2 O 6.5 (Kennedy, 1996) exhibits similar vacancy ordering and its structure is also described in F43m however this vacancy ordered structure was not seen in Pb 2 Re 2 O 7-d (Abakumov et al, 1998). It is generally believed that Re is a suitable, non-radioactive, analogue for Tc.…”

Section: Introductionmentioning

confidence: 94%

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Synthesis and Structure of Oxygen Deficient Lead-Technetium Pyrochlore, the First Example of a Valence V Technetium Oxide

et al. 2021

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The structure of lead-technetium pyrochlore has been refined in space group Fd3¯m with a = 10.36584(2) Å using a combination of synchrotron X-ray and neutron powder diffraction data and confirmed via Electron Diffraction. The oxide is found to be oxygen deficient with a stoichiometry of Pb2Tc2O7-d. Displacive disorder of the Pb cations is evident from the refinements, as has been observed in Bi2Tc2O7-d. X-ray absorption spectroscopic measurements at the Tc K-edge demonstrate the valence of the Tc is greater than 4.0 as anticipated from the refined oxygen stoichiometry. Raman spectroscopy confirms the presence of disorder leading us to conclude that this pyrochlore is the first example of a valence V technetium oxide.

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“…In the case of A = Pb, there is a certain amount of oxygen deficiency while the compounds with A = Cd can be obtained only with a stoichiometric ratio. By assuming the Vegard's law [10], the chemical formula of the single crystal was determined as Pb 2 Re 2 O 6.75 . In the pyrochlore oxides, there are two oxygen sites.…”

Section: Experiments and Sample Characterizationmentioning

confidence: 99%

Possible spin singlet quadrumerization in Pb₂Re₂O_7−δ

Michioka¹,

Kataoka²,

Ohta³

et al. 2011

J. Phys.: Condens. Matter

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A single crystal of pyrochlore Pb(2)Re(2)O(6.75) was prepared by hydrothermal synthesis, and its magnetic and transport properties were investigated. Pb(2)Re(2)O(6.75) shows the metallic conduction with an anomalous second-order structural phase transition at T(s)=294 K, in which the magnetization and the structure change similarly to that at 200 K of the superconductor Cd(2)Re(2)O(7). A three-dimensional Ising-like order parameter probed by the atomic displacement suggests that an unconventional spin singlet state is possibly realized in the ground state of Pb(2)Re(2)O(6.75), in which four spins make a quadrumer in order to remove the spin frustration of the pyrochlore lattice.

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Synthesis and Structural Study of Pb2Re2O7−xPyrochlores

Cited by 7 publications

References 5 publications

Perovskite and Pyrochlore Modifications of Pb₂MnReO₆: Synthesis, Structure, and Electronic Properties

Perovskite and Pyrochlore Modifications of Pb₂MnReO₆: Synthesis, Structure, and Electronic Properties

Synthesis and Structure of Oxygen Deficient Lead-Technetium Pyrochlore, the First Example of a Valence V Technetium Oxide

Possible spin singlet quadrumerization in Pb₂Re₂O_7−δ

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Synthesis and Structural Study of Pb2Re2O7−xPyrochlores

Cited by 7 publications

References 5 publications

Perovskite and Pyrochlore Modifications of Pb2MnReO6: Synthesis, Structure, and Electronic Properties

Perovskite and Pyrochlore Modifications of Pb2MnReO6: Synthesis, Structure, and Electronic Properties

Synthesis and Structure of Oxygen Deficient Lead-Technetium Pyrochlore, the First Example of a Valence V Technetium Oxide

Possible spin singlet quadrumerization in Pb2Re2O7−δ

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Perovskite and Pyrochlore Modifications of Pb₂MnReO₆: Synthesis, Structure, and Electronic Properties

Perovskite and Pyrochlore Modifications of Pb₂MnReO₆: Synthesis, Structure, and Electronic Properties

Possible spin singlet quadrumerization in Pb₂Re₂O_7−δ