Absence of Isotope Effect of Diffusion in a Metallic Glass

Heesemann, A.; Rätzke, Klaus; Faupel, Franz; Hoffmann, J. Elis; Heinemann, K.

doi:10.1209/0295-5075/29/3/006

Cited by 31 publications

(34 citation statements)

References 29 publications

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“…Measuring the isotope effect it has been shown that diffusion in metallic glasses is via collective motion involving numbers of particles similar to our results. 50,54 In the liquid state, upon cooling towards the glass transition, the distribution of the atomic mean square displacements deviates increasingly from a Gaussian distribution, in agreement with earlier simulations. 74 The ''rapid quench values'' for the glassy state show for sufficiently long observation times a further increase upon cooling.…”

Section: Discussionsupporting

confidence: 88%

“…Such a mechanism was, e.g., postulated for Hf diffusion in amorphous Ni 54 Zr 46 where, from pressure experiments, an activation volume for diffusion of the order of the atomic volume was deducted 47 similar to earlier results for Co diffusion. 48 The opposite result was found for Co in Co 81 Zr 19 where this mechanism was ruled out due to the vanishing activation volume.…”

Section: Introductionsupporting

confidence: 77%

“…This will certainly hold for diffusion of small atoms such as H ͑Ref. 53͒ but has also been assumed for larger atoms such as Co. 48 The very small isotope effect observed experimentally 50,54 points towards a diffusion mechanism inherent to the disordered structure. This would be in agreement with the collective jumps seen in the simulation.…”

Section: Introductionmentioning

confidence: 89%

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Collective jumps in a soft-sphere glass

1999

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Relaxations in a soft-sphere glass are studied by molecular dynamics. We observe local jumps where groups of ten and more atoms move collectively forming chainlike structures. At the lowest temperatures the total jump length is of the order of the nearest neighbor distance whereas a single atom moves only a fraction of this distance. Both the displacements and the numbers of participating atoms increase with temperature. Successive jumps tend to involve the same atoms. Relaxations and soft quasilocalized vibrations are correlated. In the glass and in the liquid state near the glass transition a markedly non-Gaussian distribution of the mean square displacements is observed. ͓S0163-1829͑99͒10601-5͔

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Section: Discussionsupporting

confidence: 88%

Section: Introductionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 89%

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Collective jumps in a soft-sphere glass

1999

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“…Besides, the isotope effect of ion diffusion in a solid has been much investigated. [10][11][12][13][14][15][16] The isotope effect of lithium ion in lithium borate glasses or lithium metal has been reported. [17][18][19][20][21][22] The temperature dependence of the diffusion coefficient D of atoms ͑of mass m͒ diffusing by a simple vacancy mechanism in a solid is expressed by the Arrhenius equation…”

mentioning

confidence: 99%

Investigation of Isotope Effect of Lithium Ion Conductivity in (La, Li)TiO[sub 3] Single Crystal

Kunugi

Kyômen

Inaguma

et al. 2002

Electrochem. Solid-State Lett.

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The lithium ion conductivities of perovskite-type oxide La 0.52(1) 6 Li 0.30(1) TiO 2.93(2) and La 0.52(1) 7 Li 0.30(1) TiO 2.93(2) single crystals, 6 and 7 , which were prepared by reproducible isotope exchange process using molten salt, were measured. The 6 / 7 ratio was almost the same as the classical theoretical value, 1.08, and the activation energies of these samples were constant.Perovskite-type oxide (La, Li)TiO 3 is known as a high lithium ion conductor, and it has been the subject of many studies. 1-9 According to the results of those studies, the crystal structure, the lattice parameters, the bottleneck size, the carrier concentration, and the vacancy concentration in the A site are known as the key parameters to adjust to obtain a high ionic conductivity. Especially, the lattice parameters are the predominant factor in ion conductivity. Besides, the isotope effect of ion diffusion in a solid has been much investigated. [10][11][12][13][14][15][16] The isotope effect of lithium ion in lithium borate glasses or lithium metal has been reported. [17][18][19][20][21][22] The temperature dependence of the diffusion coefficient D of atoms ͑of mass m͒ diffusing by a simple vacancy mechanism in a solid is expressed by the Arrhenius equationwhere E is the activation energy, f the correlation coefficient, N the fractional vacancy concentration, a the lattice constant, the attempt frequency, ⌬S the excitation entropy, and R the gas constant. The pre-exponential factor D 0 , called the frequency factor, includes the attempt frequency, which is proportional to 1/(m) 1/2 . 23 For the lithium isotope, the following isotope effect value is expected to appear in the diffusion coefficientSo, the lighter isotope 6 Li can diffuse faster than the heavier isotope 7 Li. But, in many papers, the lithium isotope effect value was reported to be different from the calculated value, 1.08, and was dependent on the temperature. 17-21 This behavior is explained by the quantum partition function. 17,18 In lithium metal, the diffusion coefficient was measured using NMR, 22 which gave the ratios of diffusion coefficients asThis result is explained by the influence of the matrix and the spatial correlation factor. 22 However, in previous reports, the isotope effect was compared between isotope samples with different compositions and structures. Therefore, strictly, the isotope effect has not been studied quantitatively and remains unclear. This study investigated the isotope effect of lithium ion conductivity in (La, Li)TiO 3 single crystals. (La, 7 Li)TiO 3 was prepared from the reproducible ion exchange process using molten salt for pristine (La, 6 Li)TiO 3 , which assures the reliability of the data. ExperimentalPolycrystalline La 0.55 Li 0.35 TiO 3 was prepared by a conventional solid-state reaction technique. La 2 O 3 ͑4 N͒, 6 Li 2 CO 3 ͑3 N; 6 Li: 7 Li ϭ 94:6), ͑or 7 Li 2 CO 3 ͑3 N; 6 Li: 7 Li ϭ 2:98͒,͒ and TiO 2 ͑4 N͒ were used as starting materials. The metal content of La 2 O 3 was determined by ethylenediaminetetraacetic acid...

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“…Whereas the activation volumes of the order of an atomic volume have been taken as evidence of diffusion via thermally generated defects, the almost vanishing activation volumes allow one to rule out any diffusion mechanism similar to vacancy diffusion in crystalline solids. In accord with very small isotope effects of Co self-diffusion [13] and results from molecular dynamics simulations [14,15], the vanishing activation volumes were attributed to a direct highly collective diffusion mechanism that does not involve thermal defects [2, 6,13].…”

mentioning

confidence: 88%

Evidence of Defect-Mediated Zirconium Self-Diffusion in AmorphousCo92Zr8

1998

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We have measured the pressure dependence of 95 Zr self-diffusion in structurally relaxed Co 92 Zr 8 glass at 698 K. The resulting activation volume of ͑0.9 6 0.1͒V, where V is the mean atomic volume, is similar to vacancy diffusion in crystalline solids. This suggests that, while Co does not diffuse via thermal defects in Co-rich Co-Zr glasses [P. Klugkist et al., Phys. Rev. Lett. 80, 3288 (1998)], Zr selfdiffusion is mediated by vacancylike defects. We thus provide evidence of the existence of an opposite Kirkendall effect in interdiffusion between certain amorphous alloys as proposed by K. N. Tu and T. C.

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Absence of Isotope Effect of Diffusion in a Metallic Glass

Cited by 31 publications

References 29 publications

Collective jumps in a soft-sphere glass

Collective jumps in a soft-sphere glass

Investigation of Isotope Effect of Lithium Ion Conductivity in (La, Li)TiO[sub 3] Single Crystal

Evidence of Defect-Mediated Zirconium Self-Diffusion in AmorphousCo92Zr8

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