Growth of Sapphire Filaments from the Melt

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

doi:10.1038/216574b0

Cited by 83 publications

(28 citation statements)

References 2 publications

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“…The shifts are to the blue rather than to the red as is observed with uniaxial compressive stress and are linear up to a tensile stress of 6 kbar, defining the yield point of the fiber. The tensile strength of the fiber was determined to be 7.7 kbar; the quality of the materials as measure by this parameter is comparable with those reported by LaBelle and Mlavsky [13]. Torsional stress can also be applied; the effects of torsional stress on the vibration Raman active modes of sapphire fiber have been reported [14].…”

Section: Characterization Of Lhpg Materialssupporting

confidence: 63%

Synthesis, characterization, and applications of shaped single crystals

Yen

1999

Phys. Solid State

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In this paper we will review techniques for the growth of single crystal mostly of insulating material which are shaped in the growth process. In particular, we will focus on the growth of single crystal fibers of optically activated materials; the emphasis will be placed on the so-called Laser Heated Pedestal Growth (LHPG) method of pulling crystalline fibers. LHPG offers a number of logistical advantages which can be exploited as a tool for materials research. Progress in the synthesis of materials using LHPG is described, as are spectroscopic techniques which are employed in characterizing the optical and physical properties of the crystal fibers obtained through this method.There has been interest on crystalline materials prepared in fiber form for a sustained period of time; this is partially because single crystal fibers occurring naturally in the form of whiskers often possess near ideal physical properties in crystallinity and in tensile strength. Earlier work addressed itself mostly to metallic materials, for example, in 1922 von Gompers [1] was successful in pulling single crystal metallic filaments directly from the melt. Later, in the 1950's, much of the work centered on the magnetic and mechanical properties of metallic whiskers [2]; however the size and composition of these could not be controlled accurately.One method which allows the growth of crystalline fibers is the so-called Stepanov method in which the melts are drawn through shapers and crystallization is made to occur after passage through a die [3]. Another method that enabled us to grow single crystal fibers of the desired length and diameter, in the proper crystallographic orientation and of proper composition and doping is the Laser Heated Pedestal Growth (LHPG) method of fiber synthesis [4].LHPG and the related float zone growth technique are micro-variants of the Czochralski growth method; the feed stoch used is generally in the shape of a rod and the melt is in the form of a self supporting bubble at the tip of the rod. A number of heating sources have been used to produce the melt; the most common method by far has been laser heating with focused single or multiple beams. A seed is dipped into the melt and is wetted by in; as the seed is pulled out, surface tension of the molten materials forms a pedestal around the seed, hence the name of pedestal growth. The melt is kept in place solely by surface tension, hence, this fiber growth method does not require crucibles and eliminates one source of sample contamination. This type of container-less growth also permits the synthesis of materials with extremely high melting points. The laser heated version of pedestal growth (LHPG) is illustrated in Fig. 1 [5].In a typical LHPG fiber pulling system, a stabilized CO 2 cw laser typically with an output of between 15-75 W is used as a heating source. The usual focusing and turning optics for the beam are shown in Fig. 2 along with the pulling and feeding mechanisms. The fiber pulling assembly may be enclosed in a vacuum-tight chamber allowin...

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Section: Characterization Of Lhpg Materialssupporting

confidence: 63%

Synthesis, characterization, and applications of shaped single crystals

Yen

1999

Phys. Solid State

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“…not sufficiently well established, as well as too different values of the saturated vapour pressure of alumina and silica 8 set serious problems in crystallising the fibres from the melt while using well-known crystallisation methods, such as EFG 9 and LHPG, 10 normally employed to produce single crystalline oxide fibres. A technique called the internal crystallisation method (ICM) 11,12 allows producing a bundle of oxide rods-like fibres under conditions that make easier to crystallise complex oxides including single crystalline mullite.…”

Section: Introductionmentioning

confidence: 99%

Single crystalline mullite fibres obtained by the internal crystallisation method: Microstructure and creep resistance

Mileiko

Serebryakov

Кийко

et al. 2009

Journal of the European Ceramic Society

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“…The first growth of profiled single crystal sapphire was published more than 40 years ago by La Belle and Mlavsky (TYCO laboratories) [2]. The "edge-defined film-fed growth" (EFG) method is in principle similar to an older one (1953) of A. V. Stepanov for growth of shaped single crystals of metals [3].…”

Section: Introductionmentioning

confidence: 99%

Preparation, properties and application of sapphire single-crystal fibers grown by the EFG method

Klejch

Němec

Kubát

et al. 2013

EPJ Web of Conferences

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Abstract. Sapphire -the single crystal of aluminum oxide (Al 2 O 3 ) -is one of the most important artificially produced materials. The sapphire fibres studied were grown in Crytur using the "edge-defined film-fed growth" (EFG) technique. Their unique physical and chemical properties can be employed in various applications. Due to their high refractive index and a broad transmission band spanning the ultraviolet, visible and infrared bands, sapphire fibres are perfect waveguides in harsh environments. The current major applications are Er:YAG laser beam delivery and pyrometric and spectrometric measurements in furnaces, combustion engines, etc. In this paper we summarize an adjustment of the EFG method to grow thin filaments by giving possible molybdenum die designs. We investigated the fibres using an optical microscope and measured their transmission of an Er:YAG laser beam (2.94 µm). The attenuation of the tested samples is approximately 0.1 dB/cm.

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Growth of Sapphire Filaments from the Melt

Cited by 83 publications

References 2 publications

Synthesis, characterization, and applications of shaped single crystals

Synthesis, characterization, and applications of shaped single crystals

Single crystalline mullite fibres obtained by the internal crystallisation method: Microstructure and creep resistance

Preparation, properties and application of sapphire single-crystal fibers grown by the EFG method

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