Growth of controlled profile crystals from the melt: Part I - Sapphire filaments

LaBelle, H.E.; Mlavsky, A. I.

doi:10.1016/0025-5408(71)90006-7

Cited by 160 publications

(39 citation statements)

References 2 publications

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“…Meniscus shaping was achieved through the use of induced RF fields, (199) twinned dendrites, (200,201) widely spaced pairs of dendrites (web Si), (202) dies, (203)(204)(205) and capillary-die combinations. (206)(207)(208)(209) These techniques all allow fast growth rates to be used since the dissipation of the latent heat of fusion is enhanced by the large surface area to volume ratio. However, there are major problems which have not been solved as yet with regard to surface nonplanarity, excessive dislocation generation, and solute segregation inhomogeneities.…”

Section: Shape Controlmentioning

confidence: 99%

Crystal Growth from the Melt

Carruthers

1975

Changes of State

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Section: Shape Controlmentioning

confidence: 99%

Crystal Growth from the Melt

Carruthers

1975

Changes of State

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“…(a) conservation of mass, r f = Rs(V f /V s )2, (5) where rf and vf are radius of the fiber and its pull rate respectively and Rs and Vs the radius and push rate of the source rod; where Q s is the heat flux in the crystal away from the growth interface, Qm is the heat flux from the melt toward the interface, Qf is the latent heat of crystallization, A is the area of interface, Ps is the density of solid, ~Hf is the latent heat, K~ and Ks are the thermal conductivity of the liquid and solid, respectively, and (dT/dx)s and (dT/dx)~ are the temperature gradient in the solid and liquid respectively; and (c) shape stability, where ¢, which is related to surface tension of the melt and its ability to wet the crystal, is the angle between the meniscus and the growth axis and ¢o is a material constant independent of fiber growth rate, diameter and zone length but not crystallographic orientation. The optimum steadystate interfacial wetting angle can be expressed by the relationship Fig.…”

Section: Single Crystal Fibersmentioning

confidence: 99%

“…Melt growth techniques which have been successfully used to produce single crystal fibers include: (1) the EFG method [5] mentioned previously, (2) pulling through a die [1], (3) Float-Zone (pedestal) Growth [53][54][55], (4) Capillary Drawing [56] (Figure 15), and (5) Pressurized Capillary-Fed Growth [57] (Figure 16). The choice of method will ultimately depend on the physical and chemical properties of the material to be grown.…”

Section: Single Crystal Fibersmentioning

confidence: 99%

“…The former led several years later to the development of the EdgeDefined Film Growth Process (EFG) [5] for the production of sapphire tubes, filaments, ribbons and other shapes for special purposes. The EFG process (which is similar to the Stepanov method) and the unidirectional casting method for single crystal turbine blades were the first shaped crystal growth methods to find practical commercial applications.…”

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confidence: 99%

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Growth of Shaped Crystals

Feigelson

1989

Crystal Growth in Science and Technology

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Shaped crystal growth refers to the growth of single crystals with a predetermined cross sectional configuration designed for a specific application. The quest to develop such techniques has been driven by the need to minimize costs associated with device fabrication such as cutting or polishing, the loss of expensive materials during these fabrication processes, and the damage created by machining processes.Perhaps the first intentionally shaped crystals were the metal filaments grown by Von Gomperz [1] in Germany in 1922 through a hole in a mica plate positioned on the melt surface. In 1938, Stepanov [2] in the USSR, began studies on the growth of shaped crystals using mechanical means to control the forces of surface tension. In his approach, the melt column was crystallized outside of the container by inserting wettable or nonwettable dies of different shapes into the melt.In the United States, work on growing sapphire filaments and single crystal superalloy jet engine turbine blades began in the late 1960's [3,4]. The former led several years later to the development of the EdgeDefined Film Growth Process (EFG) [5] for the production of sapphire tubes, filaments, ribbons and other shapes for special purposes. The EFG process (which is similar to the Stepanov method) and the unidirectional casting method for single crystal turbine blades were the first shaped crystal growth methods to find practical commercial applications.Aside from these two applications, shaped crystal growth technology would probably have remained a laboratory curiosity were it not for the energy crisis in the mid-seventies and the emergence of an urgent need to produce high quality silicon for solar cell applications. The cost of producing silicon single crystals had to be reduced dramatically to make these devices competitive with other energy sources. Increased growth rates compared with conventional methods and reduction in machining costs and material losses were necessary. Development of production methods for the preparation of high quality single crystal silicon ribbon at very high growth velocities was therefore a highly desirable approach to minimize fabrication costs. As a result, existing methods such as the Stepanov, EFG, and Dendritic Web Processes were studied for this application, and 275 H. Arend et al. (eds.), Crystal Growth in Science and Technology

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“…1) produced by the Edge-Defined Film-Fed Growth Process 11 . Cylindrical samples with a diameter of 30 mm and thickness of 1.5 mm were cut and subsequently the surfaces of the samples were epitaxial polished on both sides at CrysTec Kristalltechnologie (Berlin, Germany).…”

Section: Methodsmentioning

confidence: 99%

Dielectric breakdown of alumina single crystals

Neusel

Jelitto

Schmidt

et al. 2012

Journal of the European Ceramic Society

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The bulk breakdown behaviour of alumina single crystals with two different crystal orientations,   0 2 11 -plane (single crystal A) and   1 000 -plane (single crystal C), have been studied. Therefor plan-parallel single crystal samples were electrically loaded until dielectric breakdown was achieved. For each crystal orientation, a characteristic breakdown channel direction through the sample could be defined. In C-oriented crystals the breakdown channel originated parallel to the c-axis. For Aoriented crystals however, the breakdown channel crossed the sample in an oblique direction; the angle between crystal surface and breakdown channel was 60°. Here, the breakdown channel crossed the sample along an A-plane. Although the breakdown channel paths of A and C crystals are different, the observed breakdown strength are identical within the scatter range.

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Growth of controlled profile crystals from the melt: Part I - Sapphire filaments

Cited by 160 publications

References 2 publications

Crystal Growth from the Melt

Crystal Growth from the Melt

Growth of Shaped Crystals

Dielectric breakdown of alumina single crystals

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