Motional narrowing of 19F nuclear magnetic resonance in lead fluoride

Mahajan, M. P.; Rao, B. D. Nageswara

doi:10.1016/0009-2614(71)80148-3

Cited by 15 publications

(4 citation statements)

References 5 publications

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“…The 'immobile' ions seen in the NMR experiments are those which have not participated in a vacancy hop, as the above considerations show that the ions do not move between sites without the intercession of a vacancy (the possibility of moving between occupied and interstitial sites will be considered below). The average activation energy for vacancy hopping of 25 kJ mol −1 is consistent with the activation energies calculated from the NMR exchange rates [3,4] and NMR linewidths [20] for K + -doped samples. (The difference between this activation energy and the one discussed above for the conductivity arises from the T −1 -factor in equation (4.2).)…”

Section: Vacancy Hopping and Nmr Site Exchangesupporting

confidence: 81%

Ion mobility in α-PbF₂: a computer simulation study

Castiglione¹,

Wilson²,

Madden³

et al. 2000

J. Phys.: Condens. Matter

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Computer simulation studies of the F − -ion motion in pure and KF-doped α-PbF 2 are described. The aliovalent doping introduces vacancies into the crystal lattice which promote a significant degree of ionic motion, as witnessed by nuclear magnetic resonance and conductivity measurements. The simulations, using polarizable ionic potentials that have already been shown to reproduce the properties of the superionic conducting β-phase of PbF 2 , give results which are consistent with these experimental data. A detailed site-hopping analysis is used to clarify the mechanism of the vacancy-promoted ionic motion, which differs markedly from the mechanism responsible for the facile ion diffusion in the β-phase.

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Section: Vacancy Hopping and Nmr Site Exchangesupporting

confidence: 81%

Ion mobility in α-PbF₂: a computer simulation study

Castiglione¹,

Wilson²,

Madden³

et al. 2000

J. Phys.: Condens. Matter

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“…These results correlate well with earlier measurements of δB in the 19 F NMR spectra of (1 − x)β-PbF 2 · xMnF 2 (x Ӎ 0.01-0.036 wt %) [16], according to which δB decreases from Ӎ5.2 to 0.5 G in the range 290-350 K owing to fluoride ion motion. As reported by Mahajan and Rao [17], the peak narrows sharply starting above 263 K, which is due to fluoride ion self-diffusion. Hogg et al [18] observed the narrowing of the 19 F and 207 Pb resonances at higher temperatures (above 325 K) and pointed out with good reason that the narrowing of peaks due to ionic motion, taken alone, gives no way of ascertaining which ion, Pb 2+ or F -, diffuses.…”

Section: Nmr and Xrd Resultssupporting

confidence: 67%

“…The reported NMR data on the ion mobility in αand β-PbF 2 are somewhat contradictory [16][17][18][19][20][21][22]. These polymorphs differ markedly in structure, which shows up in the temperature variation of their 19 F NMR spectra (Figs.…”

Section: Nmr and Xrd Resultsmentioning

confidence: 99%

Synthesis, Ion Mobility, and Superionic Conductivity of (1 − x)PbF2 ⋅ xMF n (M = Li, Na, K, Rb, Cs, Zr) Solid Solutions

et al. 2005

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Ionic motion and conduction in (1 -x )PbF 2 · x ZrF 4 and (1 -x )PbF 2 · x MF (M = alkali-metal cation) solid solutions are studied by 19 F and 207 Pb NMR and impedance spectroscopy. The factors determining ionic motion in the solid solutions and their structure and energetics in the range 170-550 K are analyzed. The ionic conductivity of (1 − x )PbF 2 · x ZrF 4 with x ≤ 0.4 and 0.93PbF 2 · 0.07MF is shown to be 10 -4 to 10 -2 S/cm at temperatures above 425 K, which places these materials among superionics.

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“…Pure α PbF 2 is a moderate ionic conductor at room temperature. Studies of the bulk ionic-conductivity and the 19 F NMR static line widths of α PbF 2 suggest that fluoride-ion motion occurs via a vacancy diffusion mechanism. , The 19 F NMR spectra of α PbF 2 -1, −2, -w, and -d, presented in this paper, provide a direct method of probing local mobilities and diffusion pathways of the fluoride-ions in these samples.…”

Section: Discussionmentioning

confidence: 72%

A 1- and 2-D ¹⁹F MAS NMR Study of Fluoride-Ion Mobility in α PbF₂

Wang

Grey

1998

J. Am. Chem. Soc.

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One- and two-dimensional 19F high-speed MAS NMR are used to probe motion of the fluorine sublattices in the fluoride-ion conductors α PbF2 and potassium fluoride-doped α PbF2. The two crystallographic sites F(1) and F(2) are resolved in the 19F spectrum of the pure material and are assigned on the basis of their 207Pb−19F J-coupling. A resonance from fluoride-ions jumping rapidly between the two sites is also observed above 120 °C, which increases in intensity as the temperature is raised. The resonance from the mobile fluoride-ions is observed at room temperature for the α PbF2 sample containing potassium impurities and for samples that have been intentionally doped with KF by direct reaction of KF and PbF2. The correlation times of the rigid and mobile fluoride-ions in these samples differ by more than 2 orders of magnitude, and 2-D magnetization exchange methods show that the exchange between these two sets of fluoride-ions is negligible. The vacancies produced by potassium doping appear to remain closely associated with the potassium defects at low temperatures, and the mobile fluoride-ions at these temperatures are assigned to fluoride-ions near the potassium defects. In contrast, in the pure, or more uniformly potassium-doped, materials, the vacancies are more uniformly distributed over the solid, resulting in spectra with a narrower range of correlation times for fluoride-ion motion. Finally, a low activation energy conduction pathway between F(1) and F(2) sites along the y-axis is proposed to rationalize the rapid F(1)↔F(2) fluoride-ion diffusion.

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Motional narrowing of 19F nuclear magnetic resonance in lead fluoride

Cited by 15 publications

References 5 publications

Ion mobility in α-PbF₂: a computer simulation study

Ion mobility in α-PbF₂: a computer simulation study

Synthesis, Ion Mobility, and Superionic Conductivity of (1 − x)PbF2 ⋅ xMF n (M = Li, Na, K, Rb, Cs, Zr) Solid Solutions

A 1- and 2-D ¹⁹F MAS NMR Study of Fluoride-Ion Mobility in α PbF₂

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Motional narrowing of 19F nuclear magnetic resonance in lead fluoride

Cited by 15 publications

References 5 publications

Ion mobility in α-PbF2: a computer simulation study

Ion mobility in α-PbF2: a computer simulation study

Synthesis, Ion Mobility, and Superionic Conductivity of (1 − x)PbF2 ⋅ xMF n (M = Li, Na, K, Rb, Cs, Zr) Solid Solutions

A 1- and 2-D 19F MAS NMR Study of Fluoride-Ion Mobility in α PbF2

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Ion mobility in α-PbF₂: a computer simulation study

Ion mobility in α-PbF₂: a computer simulation study

A 1- and 2-D ¹⁹F MAS NMR Study of Fluoride-Ion Mobility in α PbF₂