7Li and 6Li Solid-State NMR Studies of Structure and Dynamics in LiNbO3−WO3 Solid Solutions

Yin, Xiang; Machida, Nobuya; Wu, Xiang; Lakeman, Charles D. E.; Wüllen, Leo van; Lange, F. F.; Levi, and Carlos; Eckert, Hellmut; Anderson, Stanley E.

doi:10.1021/jp971751z

Cited by 21 publications

(13 citation statements)

References 28 publications

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“…In this case, no coalescence of quadrupole satellites occurs, and the satellites show exactly the same narrowing as the central transition. Different ad hoc formulas exist to describe the line width Δν of the central transition as a function of the correlation time τ c − and to extract jump rates and activation energies for the Li motion. We used the implicit expression false( normalΔ ν false) 2 = false( normalΔ ν ″ false) 2 + false( normalΔ ν ′ false) 2 · 2 π · tan − 1 ( α · Δ ν · τ c ) by Abragam, where Δν is the line width at a given temperature T [for simplicity, we used the full width at half-maximum (fwhm) instead of the second moment Δν], α is a constant of the order of unity depending on the exact line shape (here chosen to be equal to one), and v ′ and v ″ describe the plateau values at very low and high temperatures, respectively.…”

Section: Resultsmentioning

confidence: 99%

Li Ion Dynamics in a LiAlO₂ Single Crystal Studied by ⁷Li NMR Spectroscopy and Conductivity Measurements

et al. 2012

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Dynamics of lithium ions in solid materials is a key parameter for applications such as electrode materials for lithium ion batteries. The Li diffusion in single crystalline γ-LiAlO 2 was studied with temperature-dependent 7 Li NMR spectroscopy and conductivity measurements. The NMR measurements include a detailed study of the temperature dependence of static spectra and spin−lattice relaxation rate measurements. A combination of these methods allowed us to study diffusion coefficients over a range of more than seven decades. The range covered was 10 −20 to 10 −13 m 2 s −1 corresponding to jump rates between 10 0 and 10 7 s −1 . An activation energy of about 1 eV was found. The hopping between crystallographically equivalent Li sites was explicitly verified by coalescence of quadrupole satellites in the NMR spectra. ■ INTRODUCTIONγ-LiAlO 2 crystallizes in the tetragonal space group P4 1 2 1 2. A unit cell of this crystal contains four formula units and has lattice parameters a = 5.1687 ± 0.0005 Å and c = 6.2679 ± 0.0006 Å. 1 There are four chemically equivalent but magnetically inequivalent sites for the Li as well as for the Al atoms. LiAlO 2 is used as a substrate material for epitaxial growth of III−V semiconductors like GaN. 2 The stability of such systems during processing and operation will depend on lithium diffusion in the substrate and from the substrate into the semiconducting films. Furthermore, LiAlO 2 is used as a coating in Li electrodes 3 and as an additive in composite Li electrolytes. 4 Again, Li diffusion is a crucial process for these applications. LiAlO 2 is also considered as a candidate material for tritium breeder or fusion reactors. 5 In this case, tritium release and diffusion will depend on lithium diffusion in this material. Therefore, molecular dynamics simulation had been carried out, which predicted a Li diffusion coefficient of 2.8 × 10 −11 m 2 /s at 600 K and an activation energy of 0.5 eV. 5 First, NMR measurements were performed on powder samples to investigate the local electronic structure at the Al sites 6 and 7 Li T 1 relaxation times. 7 The electronic structure in a single crystal of LiAlO 2 , being identical to the one used here, was studied via the orientation dependence of 7 Li NMR spectra. 8 From this, the complete electric field gradient (EFG) tensor was determined for the Li positions. In this study, we present investigations of the Li dynamics in a γ-LiAlO 2 single crystal. For this purpose, we performed temperature-dependent NMR spectroscopic studies as well as measurements of the ionic conductivity. NMR is a versatile tool to study the dynamics of, for example, Li ions in condensed matter over a large range of correlation times. 9 We examined the temperature dependence of 7 Li NMR relaxation rates and of static 7 Li NMR spectra. The latter one comprises the motional narrowing of the central transition as well as the coalescence of quadrupolar satellites. ■ SAMPLE PREPARATIONLiAlO 2 single crystals were grown using the Czochralski technique with radiofrequency induct...

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Section: Resultsmentioning

confidence: 99%

Li Ion Dynamics in a LiAlO₂ Single Crystal Studied by ⁷Li NMR Spectroscopy and Conductivity Measurements

et al. 2012

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“…The activation energy is estimated to be about 0.32 eV for amorphous LiNbO 3 and about 0.46 eV for the ball milled sample, whereas it is much higher for the microcrystalline source material, 1.07 eV. 6,27,44 Motional narrowing of the ball milled material is more comparable to that of amorphous LiNbO 3 , as has also been reported quite recently by Chadwick et al 28 In the range below 470 K the sol-gel prepared nanocrystalline material reveals no sharp decrease in linewidth with increasing temperature, like the other samples do, since its Li diffusivity is not dominated by fast diffusion pathways located in the interfacial regions. Thus, the same trend of Li diffusivity is found by NMR solidecho experiments as was obtained by conductivity measurements (see section 4.1 and ref.…”

Section: Impedance Spectroscopymentioning

confidence: 97%

NMR and impedance studies of nanocrystalline and amorphous ion conductors: lithium niobate as a model system

et al. 2007

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Lithium niobate has been chosen as a model system for spectroscopic studies of the influence of different structural forms and preparation routes of an ionic conductor on its ion transport properties. The Li diffusivity in nanocrystalline LiNbO 3 , prepared either mechanically by high-energy ball-milling or chemically by a sol-gel route, was studied by means of impedance and solid state 7 Li NMR spectroscopy. The Li diffusivity turned out to be strongly correlated with the different grain boundary microstructures of the two nanocrystalline samples and with the degree of disorder introduced during preparation, as seen especially by HRTEM and EXAFS. Although in both samples nanostructuring yields an enhancement of the Li diffusivity compared to that in coarse grained LiNbO 3 , the Li diffusivity in ball-milled LiNbO 3 is much higher than in chemically prepared nanocrystalline LiNbO 3 . The former LiNbO 3 sample has a large volume fraction of highly disordered interfacial regions which seem to be responsible for fast Li diffusion and to have a structure being very similar to that of the amorphous form. This is in contrast to the chemically prepared sample where those regions have a smaller volume fraction.

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“…It has negligible influence on our results and will not further be discussed here. Xia et al 22 have studied structure and dynamics in crystalline (LiNbO 3 ) 1Àx À (WO 3 ) x solid solutions using 7 Li and 6 Li NMR. The 7 Li spectra for x ¼ 0 reveal two distinct contributions to the NMR line, too.…”

Section: Spin-lattice Relaxationmentioning

confidence: 99%

“…Being consistent with the results from SLR measurements, E MN of amorphous LiNbO 3 is similar to the activation energy of nanocrystalline LiNbO 3 , whereas the microcrystalline form shows a higher activation energy E MN . Xia et al 22 derived from MN data via eqn. (8) an activation energy of about 1 eV for the Li diffusivity in (LiNbO 3 ) 1Àx À (WO 3 ) x crystals for x ¼ 0.…”

Section: Spin-lattice Relaxationmentioning

confidence: 99%

Diffusion in amorphous LiNbO3 studied by 7Li NMR — comparison with the nano- and microcrystalline materialDedicated to Prof. Dr Hermann Schmalzried on the occasion of his 70th birthday.

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Indris

et al. 2002

Phys. Chem. Chem. Phys.

104

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Lithium diffusion in amorphous LiNbO 3 , synthesized by a sol-gel process, was investigated by temperatureand frequency-dependent 7 Li NMR experiments. 7 Li spin-lattice relaxation rates T À1 1 and 7 Li nuclear magnetic resonance spectra, in particular line shapes and motional narrowing of the central line, were measured. The results are discussed in comparison with those on nano-and microcrystalline LiNbO 3 investigated by us earlier. The Li diffusivity in the amorphous material is much higher than in the microcrystalline one and can be described by practically the same diffusion parameters as in nanocrystalline LiNbO 3 . This suggests that the diffusion pathways in amorphous LiNbO 3 and in the interfacial regions of nanocrystalline LiNbO 3 have similar structures.

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⁷Li and ⁶Li Solid-State NMR Studies of Structure and Dynamics in LiNbO₃−WO₃ Solid Solutions

Cited by 21 publications

References 28 publications

Li Ion Dynamics in a LiAlO₂ Single Crystal Studied by ⁷Li NMR Spectroscopy and Conductivity Measurements

Li Ion Dynamics in a LiAlO₂ Single Crystal Studied by ⁷Li NMR Spectroscopy and Conductivity Measurements

NMR and impedance studies of nanocrystalline and amorphous ion conductors: lithium niobate as a model system

Diffusion in amorphous LiNbO3 studied by 7Li NMR — comparison with the nano- and microcrystalline materialDedicated to Prof. Dr Hermann Schmalzried on the occasion of his 70th birthday.

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7Li and 6Li Solid-State NMR Studies of Structure and Dynamics in LiNbO3−WO3 Solid Solutions

Cited by 21 publications

References 28 publications

Li Ion Dynamics in a LiAlO2 Single Crystal Studied by 7Li NMR Spectroscopy and Conductivity Measurements

Li Ion Dynamics in a LiAlO2 Single Crystal Studied by 7Li NMR Spectroscopy and Conductivity Measurements

NMR and impedance studies of nanocrystalline and amorphous ion conductors: lithium niobate as a model system

Diffusion in amorphous LiNbO3 studied by 7Li NMR — comparison with the nano- and microcrystalline materialDedicated to Prof. Dr Hermann Schmalzried on the occasion of his 70th birthday.

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⁷Li and ⁶Li Solid-State NMR Studies of Structure and Dynamics in LiNbO₃−WO₃ Solid Solutions

Li Ion Dynamics in a LiAlO₂ Single Crystal Studied by ⁷Li NMR Spectroscopy and Conductivity Measurements

Li Ion Dynamics in a LiAlO₂ Single Crystal Studied by ⁷Li NMR Spectroscopy and Conductivity Measurements