Local structure in a tetravalent-substituent BIMEVOX system: BIGEVOX

Yue, Yumei; Dzięgielewska, Aleksandra; Hull, S.; Whiteley, Richard M.; Toms, Harold; Małys, M.; Zhang, Man; Yan, Haixue; Abrahams, Isaac

doi:10.1039/d1ta07547k

Cited by 10 publications

(8 citation statements)

References 62 publications

(87 reference statements)

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“…Detailed average structures derived from neutron diffraction have been used to suggest models of the defect structure, ,− while more direct spectroscopic probes such as 51 V solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies as well as extended X-ray absorption fine structure (EXAFS) studies have yielded more direct evidence of local structure around cations in the vanadate layer. − Recent developments in the analysis of total scattering data using reverse Monte Carlo (RMC) modeling have allowed for a detailed characterization of local structure in other oxide ion conducting solids such as Bi 3 YO 6 and Bi 4 YbO 7.5 . , Uniquely, the resulting models can be analyzed for physical evidence of vacancy ordering. Using these methods, we have recently found evidence for a nonrandom vacancy deficiency in the (100) m direction in γ-BIGEVOX, consistent with the observed superlattice ordering in the α- and β-phases …”

Section: Introductionsupporting

confidence: 72%

“…46.1°2θ (d ≈ 1.97 Å) is less split at room temperature in BISNVOX05 (Figure S3a) and BIGEVOX10 (Figure 2a) than in the parent compound Bi 4 V 2 O 11−δ . 31 This suggests that the room temperature structures of BISNVOX05 and BIGEVOX 10 show little or no monoclinic distortion compared to the unsubstituted parent compound. Figure 2c,d shows the thermal variation of the equivalent mean cell lattice parameters and cell volume for BIGEVOX10 and BISNVOX05, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…46.1° 2θ ( d ≈ 1.97 Å) is less split at room temperature in BISNVOX05 ( Figure S3a ) and BIGEVOX10 ( Figure 2 a) than in the parent compound Bi 4 V 2 O 11−δ . 31 This suggests that the room temperature structures of BISNVOX05 and BIGEVOX 10 show little or no monoclinic distortion compared to the unsubstituted parent compound.…”

Section: Resultsmentioning

confidence: 99%

“…Using these methods, we have recently found evidence for a nonrandom vacancy deficiency in the (100) m direction in γ-BIGEVOX, consistent with the observed superlattice ordering in the αand β-phases. 31 We have previously proposed two limiting models for the defect structure in BIMEVOXes: the equatorial vacancy (EV) model, where all oxygen vacancies are located in the bridging equatorial positions, and the apical vacancy (AV) model, where the oxide ion vacancies are located in nonbridging apical positions (Figure 1). Substitution of vanadium by cations that have a different preferred coordination number can lead to polyhedral transformation in the remaining vanadium polyhedra, as seen in the BIGAVOX system where transformation of octahedral vanadium to pentacoordinate and tetrahedral vanadium occurs as more gallium is introduced into the system.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Local Structure in α-BIMEVOXes (ME = Ge, Sn)

et al. 2022

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The BIMEVOXes are among the best oxide ion conductors at low and intermediate temperatures. Their high conductivity is associated with local defect structure. In this work, the local structures of two BIMEVOX compositions, Bi 2 V 0.9 Ge 0.1 O 5.45 and Bi 2 V 0.95 Sn 0.05 O 5.475 , are examined using total neutron and X-ray scattering methods, with both compositions exhibiting the ordered α-phase at 25 °C and the disordered γ-phase at 700 °C. While the diffraction data for the α-phase do not allow for the polar (C2) and nonpolar (C2/m) structures to be readily distinguished, measurements of dielectric permittivity suggest the αphase is weakly ferroelectric in character, consistent with calculations of spontaneous polarization based on a combination of density functional calculations and machine learning methodology. Reverse Monte Carlo (RMC) analysis of total scattering data reveals Ge preferentially adopts tetrahedral geometry at both temperatures, while Sn is found to predominantly adopt octahedral coordination in the α-phase and tetrahedral coordination in the γ-phase. In all cases, V polyhedra are found to consist of tetrahedral, pentacoordinate, and octahedral geometries, as also predicted by the crystallographic analysis and confirmed by 51 V solid state NMR spectroscopy. Although similar long-range structures are observed at room temperature, the oxide ion vacancy distributions were found to be quite different between the two studied compositions, with a nonrandom deficiency in vacancy pairs in the secondnearest shell along the ⟨100⟩ tetragonal direction for BIGEVOX10, compared with a long-distance (>8.0 Å) ordering of equatorial vacancies for BISNVOX05. This is attributed to the differences in the preferred coordination geometries of the substituent cations in the two systems. Impedance spectroscopy measurements reveal both compositions show high conductivity in the order of 10 −1 S cm −1 at 600 °C.

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Section: Introductionsupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

“…46.1° 2θ ( d ≈ 1.97 Å) is less split at room temperature in BISNVOX05 ( Figure S3a ) and BIGEVOX10 ( Figure 2 a) than in the parent compound Bi 4 V 2 O 11−δ . 31 This suggests that the room temperature structures of BISNVOX05 and BIGEVOX 10 show little or no monoclinic distortion compared to the unsubstituted parent compound.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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