Chemical diffusion in alkali halides

Lindström, R.

doi:10.1016/0022-3697(69)90321-7

Cited by 16 publications

(2 citation statements)

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“…The principal objectives of the present study were as follows: (1) To examine the interdiffusion in ABO 3 -ABЈO 3 diffusion couples (i.e., with different cations on the B-sublattice), both theoretically and experimentally: The BaTiO 3 -BaZrO 3 system was investigated in the present work. (2) To obtain qualitative estimates of the relative magnitudes of the diffusivities of the various species by using site-specific doping strategy: In our earlier work, 10 it was demonstrated that the diffusion as well as the extent of the Kirkendall porosity can be drastically enhanced /suppressed by enhancing/suppressing specific kinds of point defects in these materials by sitespecific aliovalent doping. For these reasons, the effect of Bsite acceptor and donor doping on porosity formation and interdiffusion has been explored.…”

Section: (4) Objectives Of the Present Investigationmentioning

confidence: 99%

Interdiffusion and Kirkendall Effect in Doped BaTiO₃–BaZrO₃ Perovskites: Effect of Vacancy Supersaturation

Gopalan

Virkar

1999

Journal of the American Ceramic Society

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Interdiffusion in Sc-doped and Ta-doped BaTiO 3 -BaZrO 3 perovskites was examined, both theoretically and experimentally. Analytical expressions for the lattice velocity, v, and the interdiffusion coefficient, D , were obtained. The v and the D were numerically evaluated as a function of dopant type (trivalent-acceptor or pentavalent-donor) and concentration using literature values of oxygen vacancy diffusivity, D V O , the A-site vacancy diffusivity, D V A , and assumed values for the B-site vacancy diffusivities, D V B and D V B . Regardless of the chosen values of D V B and D V B , the calculated D increased with the Ta concentration and decreased with the Sc concentration. The dependence (shape) of the calculated v vs dopant type and concentration, however, was a function of the magnitudes of D V A and D V B . For D V A < (D V B , D V B ) < D V O , the calculated v exhibited a maximum at ∼0.8% acceptor dopant. Diffusion couples in the BaTiO 3 -BaZrO 3 system doped with either Sc (acceptor) or Ta (donor) were annealed in air over a temperature range between 1300°and 1500°C. Extensive Kirkendall porosity was observed in several samples. The measured porosity vs dopant concentration (acceptor/donor) trace was similar to that of calculated v vs dopant concentration (acceptor/ donor). However, the measured D vs dopant concentration (acceptor/donor) was not in accord with the calculations.This difference is attributed to a nonequilibrium vacancy supersaturation and the accompanying porosity formation. To obtain further evidence of the deviation from equilibrium, experiments were also conducted on both coarsegrained and fine-grained samples. The coarse-grained samples, which are expected to have fewer vacancy sinks and sources, exhibited greater Kirkendall porosity and greater D values compared to the fine-grained samples, consistent with a greater deviation from equilibrium.

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Section: (4) Objectives Of the Present Investigationmentioning

confidence: 99%

Interdiffusion and Kirkendall Effect in Doped BaTiO₃–BaZrO₃ Perovskites: Effect of Vacancy Supersaturation

Gopalan

Virkar

1999

Journal of the American Ceramic Society

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“…In an interdiffusion experiment there is a real possibility to make a definitive set of experiments. In [7,[12][13][14][15] it was shown that the interdiffusion process on cation sublattice(s) in ionic materials depends strongly on the mobility of the anions (and vice versa). A similar argument is appropriate for the case of LSGM for the two cation sublattices that must affect interdiffusion processes of each other.…”

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Diffusion Kinetics Analysis of Cation Diffusion in YSZ and LSGM

Belova¹,

Murch²,

Samuelis

et al. 2008

DDF

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In this paper, we discuss different possible cation diffusion mechanisms in YSZ and LSGM. Monte Carlo simulations are also reported of tracer diffusivities in LSGM for a postulated cluster mechanism. These simulations extend earlier simulations on un-doped material. The limits of the ratio of the diffusivities are consistent with experimental tracer diffusion findings over a wide range of cation-vacancy exchange frequencies. We also develop relationships between the phenomenological coefficients and use these relationships to predict possible demixing and interdiffusion experimental outcomes.

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Effect of Uniaxial Stress on the Interdiffusion in the KClKBr System

Aaltonfn

Ltndström

1987

Phys. Stat. Sol. (a)

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BYDiffusion phenomena in single alkali halides are nowadays vastly studied and recently more attention has been paid to mixed alkali halides. Generally, diffusion in compound solid solutions is not well known and because mixed alkali halides possess by far the simplest defect structure they may s e r v e as good model substances to develop the basic ideas. Here we shall discuss the chemical interdiffusion which has been successfully interpreted by Manning' s theory /1, 2/ for binary metal couples. We extended it to the ionic systems /3 to 6/.The theories describe reasonably well the chemical interdiffusion coefficient 5 and the Kirkendall shift in metal systems, and 5 in the KC1-RbCl system. However, both approaches deal only with isolated vacancies although there a r e evidences for bound divacancies in metals /7/ and vacancy pairs in alkali halides /8 to lo/. As a f i r s t step to include the latter effect we have evaluated the correlation factors for vacancy-pair diffusion in NaC1-type mixed crystals /ll/, On the other hand, careful experimental data for mixed crystals are s c a r c e .

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Chemical diffusion in alkali halides

Cited by 16 publications

References 3 publications

Interdiffusion and Kirkendall Effect in Doped BaTiO₃–BaZrO₃ Perovskites: Effect of Vacancy Supersaturation

Interdiffusion and Kirkendall Effect in Doped BaTiO₃–BaZrO₃ Perovskites: Effect of Vacancy Supersaturation

Diffusion Kinetics Analysis of Cation Diffusion in YSZ and LSGM

Effect of Uniaxial Stress on the Interdiffusion in the KClKBr System

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Chemical diffusion in alkali halides

Cited by 16 publications

References 3 publications

Interdiffusion and Kirkendall Effect in Doped BaTiO3–BaZrO3 Perovskites: Effect of Vacancy Supersaturation

Interdiffusion and Kirkendall Effect in Doped BaTiO3–BaZrO3 Perovskites: Effect of Vacancy Supersaturation

Diffusion Kinetics Analysis of Cation Diffusion in YSZ and LSGM

Effect of Uniaxial Stress on the Interdiffusion in the KClKBr System

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Interdiffusion and Kirkendall Effect in Doped BaTiO₃–BaZrO₃ Perovskites: Effect of Vacancy Supersaturation

Interdiffusion and Kirkendall Effect in Doped BaTiO₃–BaZrO₃ Perovskites: Effect of Vacancy Supersaturation