Positron-annihilation studies of free-volume changes in the bulk metallic glass<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Zr</mml:mi></mml:mrow><mml:mrow><mml:mn>65</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mn>7.5</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ni</mml:mi><

Nagel, Christoph; Rätzke, Klaus; Schmidtke, E.; Faupel, Franz; Ulfert, W.

doi:10.1103/physrevb.60.9212

Cited by 94 publications

(51 citation statements)

References 17 publications

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“…This is in a general agreement with a suggestion made by Nagel et al for Ni-and Be-containing Zr based alloys. 28,29) It should be pointed out here, however, that the observed PL in the present study represents an average value of lifetimes of positrons that annihilated at different open volumes within single specimen. This means that the present technique can not probe a possible distribution of PL.…”

Section: Relaxation Behaviormentioning

confidence: 56%

“…24) As for Zrbased metallic glasses, there also exist several reports on PL and Doppler broadening measurements. [26][27][28][29][30] For example, Flores et al reported, in the study of straining and hydrogen charging effects on Zr-Ti-Ni-Cu-Be glasses, showed that annealing at 348 K slightly decreases PL, whereas that straining and hydrogen charging resulted in the increase and decrease of PL, respectively. 30) They attributed the observed increase in PL to an increase in open volume by the plastic strain.…”

Section: Relaxation Behaviormentioning

confidence: 99%

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Relaxation and Crystallization Behavior of the Zr50Cu40Al10 Metallic Glass

et al. 2005

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We examined relaxation and crystallization behavior of the ternary Zr 50 Cu 40 Al 10 metallic glass by using positron annihilation and transmission electron microscopy (TEM). Observed changes in positron annihilation lifetime of the alloy annealed isothermally at 673 K, which is below the glass transition temperature, correlate well with observed density changes; while coincidence Doppler broadening (CDB) spectra exhibit no significant change. These observations demonstrate that free volume decreases without a rearrangement of atoms during structural relaxation. On the other hand, CDB spectrum has exhibited considerable changes when the same alloy was annealed at 773 K. TEM observations suggested that crystallization occurs via growth of spherulites of several hundred nm in diameter, which themselves are composed of radially grown grains. Chemical analysis revealed that Cu atoms are partitioned out during the growth of the spherulites. Diffraction study indicated that the unit cell of the crystalline phase belong to an orthorhombic system with a ¼ 0:892, b ¼ 0:550, and c ¼ 1:060 nm; while remaining interspherulite regions are found to crystallize into an fcc phase with a ¼ 1:28 nm, which is probably isostructural to the 3 phase.

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Section: Relaxation Behaviormentioning

confidence: 56%

Section: Relaxation Behaviormentioning

confidence: 99%

Relaxation and Crystallization Behavior of the Zr50Cu40Al10 Metallic Glass

et al. 2005

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“…(The concept of "shear transition zones" [3] is also used in the context of non-equilibrium mechanical response.) The generation or disappearance of free volume has been invoked to explain shear banding [4] and positron annihilation [5] in metallic glasses.…”

Section: Introductionmentioning

confidence: 99%

Free volume cannot explain the spatial heterogeneity of Debye–Waller factors in a glass-forming binary alloy

Widmer‐Cooper

Harrowell

2006

Journal of Non-Crystalline Solids

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We examine the relation between the free volume per particle and the variance of the particle position, equivalent to a local Debye-Waller (DW) factor for a 2D glassforming alloy using molecular dynamics simulations. We find that the latter quantity exhibits significant spatial heterogeneity despite involving trajectories two orders of magnitude shorter than those typically used to measure such heterogeneities. We find that the free volume exhibits no significant spatial correlation with the local DW factor. We conclude that the spatial variation in local free volume is not the cause of the short time dynamic heterogeneity.

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“…τ 2 reflects mainly the process of positron captured in the imperfect areas inside the materials; it can characterize the intrinsic structure and preparation quality of samples. If positrons annihilate in the imperfections, such as oxygen vacancy, twin boundary, dislocation, and cation vacancies, τ 2 will be larger, sometimes it is noted as τ 3 , generally τ 3 > 800 ps [43][44][45]. Our samples do not contain τ 3 component, this indicates the credibility of the sample quality.…”

Section: Positron Experimentsmentioning

confidence: 64%

Superconductivity without dependence on valence electron density in (Al, Zn, Co) doped YBCO systems

Zhang

Wang

2010

Low Temperature Physics

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We adopted the x-ray diffraction, oxygen contents, positron annihilation technology and simulation methods to investigate systematically YBa 2 Cu 3-x (Al, Zn, Co) x O 7-δ (x = 0-0.5) cuprates. The experimental results and simulated calculations support the existence of cluster effect. Moreover, it is concluded that the cluster effect is an important factor on suppression of the superconductivity and the T c does not depend directly on the density of valence electron in the samples.

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Positron-annihilation studies of free-volume changes in the bulk metallic glassZr65Al7.5Ni<

Cited by 94 publications

References 17 publications

Relaxation and Crystallization Behavior of the Zr<SUB>50</SUB>Cu<SUB>40</SUB>Al<SUB>10</SUB> Metallic Glass

Relaxation and Crystallization Behavior of the Zr<SUB>50</SUB>Cu<SUB>40</SUB>Al<SUB>10</SUB> Metallic Glass

Free volume cannot explain the spatial heterogeneity of Debye–Waller factors in a glass-forming binary alloy

Superconductivity without dependence on valence electron density in (Al, Zn, Co) doped YBCO systems

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