Defect Formation During Crystal Growth from the Melt

Rudolph, P.

doi:10.1007/978-3-540-74761-1_6

Cited by 28 publications

(28 citation statements)

References 144 publications

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“…These striations can be either kinetically or thermally induced; the former appear for a discontinuous, step-by-step growth mode of the crystals, whereas the latter are generated by unsteady growth rates that lead to variations in the distribution constant determining the composition. 13 The pattern formation observed in the present colloidal crystals appears to be thermally induced, since the formation of large grains was not observed during the crystallization. In contrast, the stripe patterns observed in our previous study, where lamella-shaped crystal grains were formed, appeared to correspond to the kinetically induced mechanism.…”

Section: 14mentioning

confidence: 57%

“…We think that the stripe patterns observed here are closely analogous to the "striation" patterns observed in crystalline materials that results from the short-range composition fluctuations found in nearly all crystals. 13 Aqueous dispersions of colloidal silica particles (KE-W10, Japan Catalyst Co., Ltd., Tokyo, Japan) were used after they were first purified by dialysis for four months and then purified using an ion-exchange method. The particle diameter, determined by the dynamic light-scattering method, was 105 nm.…”

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confidence: 99%

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Striation Pattern of Impurity Particles in Charged Colloidal Crystals Formed by Stepwise Thermally Induced Crystallization

et al. 2012

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Charged colloids form "crystal" structures, wherein the colloidal particles are regularly arranged as a result of strong electrostatic interparticle interactions. We have reported that silica colloids containing pyridine (Py) form colloidal crystals upon heating. Herein, we report that in Py + silica colloids including small numbers of fluorescent polystyrene (PS) particles, the PS particles are arranged in stripe patterns upon stepwise unidirectional crystallization when the temperature is increased by 1°C every 10 and 15 min. We think that the present stripe patterns are closely analogous to the thermally induced striations found in a number of crystalline materials.Charged colloidal particles self-assemble to form "crystal" structures when the electrostatic interactions among the particles are sufficiently strong. In the crystal states, the colloidal particles are regularly arranged in body-centered or face-centered cubic lattices. 14We have reported that colloidal silica containing pyridine (Py) exhibits thermally induced crystallization. 5,6 Silica particles have weakly acidic silanol groups (SiOH) on their surfaces, which partly dissociate to provide surface charges. On addition of Py, the dissociation of silanol groups is enhanced, resulting in an increase in the particle charge number Z, that is, the electrostatic interaction becomes stronger. Since dissociation of Py increases with temperature (T), the silica + Py colloids crystallize upon heating, under appropriate conditions. Furthermore, we reported that impurity particles added to the silica crystal are excluded from the crystal grains and accumulate in the crystal grain boundaries. 7 In particular, stripe patterns were observed in charged silica + polystyrene (PS) binary colloids after unidirectional crystallization driven by diffusion of Py. 812 This pattern formation was explainable in terms of a combination of (1) development of thin, lamellashaped crystal grains and (2) exclusion of the PS particles from the grains to the crystal grain boundaries.In the present study, we report the formation of another type of stripe pattern in silica + PS binary colloids, which is observed after unidirectional crystallization when the temperature is varied in a stepwise manner. We think that the stripe patterns observed here are closely analogous to the "striation" patterns observed in crystalline materials that results from the short-range composition fluctuations found in nearly all crystals. 13Aqueous dispersions of colloidal silica particles (KE-W10, Japan Catalyst Co., Ltd., Tokyo, Japan) were used after they were first purified by dialysis for four months and then purified using an ion-exchange method. The particle diameter, determined by the dynamic light-scattering method, was 105 nm. An aqueous dispersion of fluorescent PS particles (G300, Thermo Scientific Inc., Waltham, MA, USA, diameter: 333 nm) was purified using an ion-exchange method. In the binary colloids used for the experiments, the volume fractions of silica (º silica ) and PS particles (º...

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Section: 14mentioning

confidence: 57%

mentioning

confidence: 99%

Striation Pattern of Impurity Particles in Charged Colloidal Crystals Formed by Stepwise Thermally Induced Crystallization

et al. 2012

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“…The broken curve shows the theoretical Scheil distribution with ko = 2 (the equilibrium segregation coefficient of carbon) in case of conservative growth regime with complete melt mixing (ko = keff) and starting concentration xCo = 5 × 10 14 cm −3 (adapted from ref. [4]). …”

Section: Extrinsic Point Defects Incorporationmentioning

confidence: 93%

“…increasing entropy, that leads proportionally to the reduction of potential of Gibbs G = H − TS, with H -enthalpy, T -absolute temperature and S -entropy. For instance, in a crystal with constituents or vacancies the energetic minimum occurs when a certain content n* is presented as (3.1) with N -total number of sites in a crystal lattice, Ed -point defect formation energy and k -Boltzmann constant [4,6] ( Fig. 1).…”

Section: Thermodynamic Considerationsmentioning

confidence: 99%

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Fundamentals and engineering of defects

Rudolph

2016

Progress in Crystal Growth and Characterization of Materials

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Velocity measurements in the liquid metal flow driven by a two-phase inductor

Pedcenko¹,

Bojarēvičs²,

Priede³

et al. 2013

Exp Fluids

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We present the results of velocity measurements obtained by ultrasonic Doppler velocimetry and local potential probes in the flow of GaInSn eutectic melt driven by a two-phase inductor in a cylindrical container. This type of flow is expected in a recent modification to the floating zone technique for the growth of small-diameter single intermetallic compound crystals. We show that the flow structure can be changed from the typical two toroidal vortices to a single vortex by increasing the phase shift between the currents in the two coils from 0 • to 90 • degrees. The latter configuration is thought to be favourable for the growth of single crystals. The flow is also computed numerically, and a reasonable agreement with the experimental results is found. The obtained results may be useful for the design of combined two-phase electromagnetic stirrers and induction heaters for metal or semiconductor melts.

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Defect Formation During Crystal Growth from the Melt

Cited by 28 publications

References 144 publications

Striation Pattern of Impurity Particles in Charged Colloidal Crystals Formed by Stepwise Thermally Induced Crystallization

Striation Pattern of Impurity Particles in Charged Colloidal Crystals Formed by Stepwise Thermally Induced Crystallization

Fundamentals and engineering of defects

Velocity measurements in the liquid metal flow driven by a two-phase inductor

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