A New Solid Solution Series Linking LiTi2O4and Li2Ti3O7Ramsdellites: A Combined X-Ray and Neutron Study

Gover, Richard K. B.; Irvine, John T. S.

doi:10.1006/jssc.1998.7948

Cited by 18 publications

(12 citation statements)

References 19 publications

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“…However, the evidence given in ref is not conclusive since the sample studied in that paper presented a noticeable amount of an unidentified impurity and the agreement factors given were higher than desirable. A slightly different distribution of lithium ions within the tunnels was reported by Gover and Irvine by combining XRD and NPD data collected on a pure sample, confirming a mixed occupation by Ti and Li of the framework octahedra in Li 2 Ti 3 O 7 , but removing any lithium from 8d positions. Interestingly, in a different paper those authors, also using neutron and XRD, found no evidence to support a partial occupancy by lithium of octahedral sites in the ramsdellite LiTi 2 O 4 .…”

Section: Introductionmentioning

confidence: 50%

“…Neutron diffraction is much more suited for that; however, even using neutron diffraction, locating lithium in Li 2 Ti 3 O 7 is not easy. Indeed, we simulated NPD patterns (not shown) for both models proposed in ref , and the difference in peak intensities is less than 3%, which is lower than the difference between calculated and experimental patterns reported in NPD studies of this material. − Even more, we refined the NPD pattern corresponding to the starting ramsdellite-Li 2 Ti 3 O 7 used in ref to obtain the proton-exchanged material, placed into the public-domain PowBase . As for all the other similar structural studies reported, the arguments in favor of model-I ((Li 2.29 ) c (Ti 3.43 ◻ 0.57 ) f O 8 ) or model−II ((Li 1.72 ) c (Ti 3.43 Li 0.57 ) f O 8 ) are crystallographycally weak.…”

Section: Resultsmentioning

confidence: 96%

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Insight into Ramsdellite Li₂Ti₃O₇ and Its Proton-Exchange Derivative

et al. 2009

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Despite being proven to be a good lithium-ion conductor 30 years ago, the crystal structure of the ramsdellite-like Li(2)Ti(3)O(7) has remained uncertain, with two potential models for locating the lithium ions in the structure. Although the model presently accepted states that both lithium and titanium occupy the octahedral sites in the framework, evidence against this model are provided by (6)Li and (7)Li MAS NMR spectroscopy. Thus, about 14% of these octahedral positions are empty since no lithium in octahedral coordination is present in the material. When Li(2)Ti(3)O(7)-ramsdellite is treated with nitric acid a complete exchange of lithium by protons is produced to yield H(2)Ti(3)O(7). The crystal structure of this proton-exchanged ramsdellite has been re-examined combining X-ray diffraction (XRD), neutron powder diffraction (NPD), and spectroscopic ((1)H and (7)Li MAS NMR) techniques. Two kinds of protons are present in this material with different acidity because of the local environments of oxygen atoms to which protons are bonded, namely, low acidic protons strongly bonded to highly charged oxygen atoms (coordinated to two Ti(4+) and a vacancy); and protons linked to low charged oxygen atoms (bonded to three Ti(4+) ions) which will display a more acidic behavior. H(2)Ti(3)O(7) absorbs water; proton mobility is enhanced by the presence of absorbed water, giving rise to a large improvement of its electrical conductivity in wet atmospheres. Thus, it seems that water molecules enter the tunnels in the structure providing a vehicle mechanism for proton diffusion.

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Section: Introductionmentioning

confidence: 50%

Section: Resultsmentioning

confidence: 96%

Insight into Ramsdellite Li₂Ti₃O₇ and Its Proton-Exchange Derivative

et al. 2009

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“…First-principles calculations by Koudriachova strongly suggest that the third phase, which is formed at high lithium content and is metastable with respect to the distorted rocksalt phase, corresponds to a structure whereby the tunnel lithium ions are in 6-fold coordination, as opposed to 4-fold coordination in the phases of lower Li content. Gover and Irvine synthesized a solid solution series linking the LiTi 2 O 4 and Li 2 Ti 3 O 7 ramsdellite phases and all the members of the series showed high capacity, as demonstrated subsequently by Gover et al…”

Section: Introductionmentioning

confidence: 77%

Computer Simulation of the Phase Stabilities of Lithiated TiO₂ Polymorphs

et al. 2010

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The structure and phase stability of a series of lithiated titania polymorphs were determined using energy minimizations of the periodic bulk crystal structures and both density functional theory (DFT) and a potential shell model. The DFT calculations were performed spin unrestricted following the linear combination of atomic orbital approach with the B3LYP exchange-correlation potential. For the potential shell model, a new set of force field parameters was derived, independently of the DFT calculations, to describe the lithium−lattice interactions. The eight polymorphs considered in this study are the rutile, anatase, brookite, TiO2−B, ramsdellite, hollandite, spinel, and hexagonal structures. The lithium to titanium ratio, x, of each lithiated titania polymorph was varied from 0.0 to 1.0 with 0.25 increments. The potential model predictions were found to be in good agreement with the structure and energetics of the lithiated titania polymorphs determined from DFT calculations, at all lithium contents. Both computational approaches indicate the following relationships. The naturally occurring titania polymorphs (i.e., rutile, anatase, brookite, and TiO2−B) were found to be the most stable of the eight phases in the absence of lithium. Anatase, brookite, and ramsdellite become energetically favored over rutile upon lithium insertion. The hexagonal and spinel polymorphs have stabilities approaching that of rutile with increasing lithium content and showed essentially equivalent total energies for x = 1.0. This prediction is consistent with numerous experimental studies, which have reported that rutile electrodes, in particular those that consist of nanomaterials, can undergo phase transformations to the hexagonal or spinel structure upon lithium insertion. The calculations indicate that the main factors controlling the relative stability of the lithiated titania polymorphs are the lithium bonding environment, the arrangement of LiO x and TiO6 polyhedra, and the extent of lattice deformation upon lithiation.

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“…A similar study was carried out by Inukai et al, 25 in which powder samples were produced by (1) reacting Li 2 CO 3 and TiO 2 in an H 2 atmosphere 26-28 and (2) using Li 4/3 Ti 5/3 O 4 as a precursor and reacting it with TiO 2 and Ti metal. [29][30][31] Also, Murphy et al 32 found that topotactic lithium insertion into the anatase polymorph of TiO 2 produces Li 0.5 TiO 2 , which, on heating to 450-500°C, is transformed irreversibly from the orthorhombic to the cubic LiTi 2 O 4 spinel phase. Annealing this powder at 750-800°C for several days produces clean samples without defects.…”

Section: (1) Powdersmentioning

confidence: 96%

Superconductivity in the Spinel Compound LiTi2O4

Moshopoulou

1999

Journal of the American Ceramic Society

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LiTi 2 O 4 has been the subject of considerable experimental and theoretical interest since the discovery of its superconductivity by Johnston et al. 1 This unique, low-T c (11.2 K) spinel oxide superconductor exhibits unusual characteristics, and interestingly, it presents properties that depend on various defects of the spinel structure. This article reviews experimental and theoretical studies of LiTi 2 O 4 and discusses the basic, unresolved issues regarding the physics of this system. Special emphasis is given to methods for preparing the compound and to the structure-properties relationship.

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A New Solid Solution Series Linking LiTi2O4and Li2Ti3O7Ramsdellites: A Combined X-Ray and Neutron Study

Cited by 18 publications

References 19 publications

Insight into Ramsdellite Li₂Ti₃O₇ and Its Proton-Exchange Derivative

Insight into Ramsdellite Li₂Ti₃O₇ and Its Proton-Exchange Derivative

Computer Simulation of the Phase Stabilities of Lithiated TiO₂ Polymorphs

Superconductivity in the Spinel Compound LiTi2O4

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A New Solid Solution Series Linking LiTi2O4and Li2Ti3O7Ramsdellites: A Combined X-Ray and Neutron Study

Cited by 18 publications

References 19 publications

Insight into Ramsdellite Li2Ti3O7 and Its Proton-Exchange Derivative

Insight into Ramsdellite Li2Ti3O7 and Its Proton-Exchange Derivative

Computer Simulation of the Phase Stabilities of Lithiated TiO2 Polymorphs

Superconductivity in the Spinel Compound LiTi2O4

Contact Info

Product

Resources

About

Insight into Ramsdellite Li₂Ti₃O₇ and Its Proton-Exchange Derivative

Insight into Ramsdellite Li₂Ti₃O₇ and Its Proton-Exchange Derivative

Computer Simulation of the Phase Stabilities of Lithiated TiO₂ Polymorphs