scholarly journals Growth of Single Crystals of Mercuric Iodide on the Ground and in Space

1993 ◽  
Vol 302 ◽  
Author(s):  
L. van den Berg
Keyword(s):  
Crystal Growth ◽  
Electronic Properties ◽  
Single Crystals ◽  
Growth Process ◽  
Short Review ◽  
Structural Quality ◽  
Mercuric Iodide ◽  
Reduced Gravity ◽  
Growth System ◽  
Growth Experiments

ABSTRACTA short review will be given of the methods by which mercuric iodide is prepared and purified to obtain material suitable for the growth of single crystals. The method used in our laboratory to grow single crystals up to 1,000 grams in weight from the vapor will be discussed. The effects of gravity on the growth process will be described.A crystal growth system suitable for operation in the reduced gravity environment of space was designed, and crystal growth experiments were performed during the flights of Spacelab 3 (April 1985) and the International Microgravity Laboratory (IML-1) (January 1992). The structural quality and electronic properties of the ground-based and spacegrown crystals were compared, and the results will be presented.

Mass Transfer in Closed Ampoule Vapor Crystal Growth

1981 ◽  
Vol 9 ◽  
Author(s):  
Franz Rosenberger
Keyword(s):  
Mass Transfer ◽  
Crystal Growth ◽  
Single Crystals ◽  
Transport Processes ◽  
Vapor Transport ◽  
Reduced Gravity ◽  
Transport Studies

EXPANDED ABSTRACTClosed ampoule vapor transport techniques are widely employed for the preparation of single crystals [1–5]. The experimental simplicity of these techniques makes them also attractive for fundamental crystal growth transport studies in reduced gravity environments. However, the underlying transport processes are complex and difficult to quantify.

Synthesis of R2 Fe14 B Single Crystals

1987 ◽  
Vol 96 ◽  
Author(s):  
B. N. Das ◽  
N. C. Koon
Keyword(s):  
Rare Earth ◽  
Crystal Growth ◽  
Single Crystals ◽  
Growth Process ◽  
Alloy Composition ◽  
Crystal Quality ◽  
Solidification Microstructure ◽  
Growth Processes ◽  
Crystal Growth Process ◽  
Isomorphous Replacement

ABSTRACTSingle crystals of R2 Fe14 B weighing 5 to 15 g were grown from a liquid melt by tri-arc and levitation Czochralski methods. The arc method was used for the growth of smaller size crystals from 5 to 7 g, and the levitation method was used for the growth of larger sizes, from 10 to 15 g. Crystals of (R1)2 –x(R2)xFe14 B could also be grown with isomorphous replacement of rare earth atoms. The starting alloy composition for the crystal growth process was chosen based on solidification microstructure. In this paper we discuss the solidification microstructure, isomorphous replacement, seeding and their interactions with the crystal growth processes and crystal quality.

Effect of New Thermal Insulation to the Growth of LiNbO3 Single Crystal by Czochralski Method

2013 ◽  
Vol 701 ◽  
pp. 108-112
Author(s):  
W.H.A. Kamaruddin ◽  
Hamdan Hadi Kusuma ◽  
Zuhairi Ibrahim
Keyword(s):  
Crystal Growth ◽  
Single Crystal ◽  
Thermal Insulation ◽  
Growth Process ◽  
Thermal Environment ◽  
Czochralski Method ◽  
Control Power ◽  
Air Atmosphere ◽  
Growth System ◽  
Hot Zone

Single crystal of LiNbO3has been successfully grown by the Czochralski method in an air atmosphere with a r.f heating crystal growth system namely Automatic Diameter Control Crystal Growth System (ADC-CGS). This paper reports on the effect of new thermal insulation on the growth process of LiNbO3single crystal. The effect of hot zone thermal insulation design was investigated. The conditions required to grow high quality LiNbO3single crystals are described. A set of crystal growth processes were conducted with the rotation rate of the seed at 15 rpm and the pulling rate at 2.0 mm/hr kept constant. All of the runs were grown along <104> orientation. To control the diameter of the crystal, we have to alter the thermal environment inside the hot zone. In other words, during the crystal growth we have to increase the control power to get smaller diameter and decrease the control power to get larger diameter.

scholarly journals Primary and secondary dendrite spacing of Ni-based superalloy single crystals

2009 ◽  
Vol 74 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Slobodanka Kostic ◽  
Aleksandar Golubovic ◽  
Andreja Valcic
Keyword(s):  
Crystal Growth ◽  
Temperature Gradient ◽  
Single Crystals ◽  
Gradient Method ◽  
Dendrite Spacing ◽  
Published Data ◽  
Bridgman Technique ◽  
Spontaneous Nucleation ◽  
Vertical Furnace ◽  
Growth Experiments

Ni-based superalloy single crystals were grown by different methods (gradient method and Bridgman technique with spontaneous nucleation and with seed). In all crystal growth experiments using the Bridgman technique, the temperature gradient along the vertical furnace axes was constant (G = 33.5 ?C/cm). The obtained single crystals were cut, mechanical and chemical polished, and chemically etched. Using a metallographic microscope, the spacing of the primary and secondary dendrites was investigated. The dendrite arm spacing (DAS) was determined using a Quantimet 500 MC. The obtained results are discussed and compared with published data.

scholarly journals Apparatus for crystal growth

2005 ◽  
Vol 38 (2) ◽  
pp. 368-369
Author(s):  
B. Cabric ◽  
T. Pavlovic
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Growth Process ◽  
Crystallization Rate ◽  
School Laboratory

The design of an apparatus based on Bridgman's method, enabling visualization of the growth process and regulation of the crystallization rate, for obtaining single crystals from a melt in a school laboratory is presented. Conditions for obtaining single crystals of several substances are given.

The use of NiMnSb Heusler alloy in MBE Grown Tunnel Junction

2001 ◽  
Vol 690 ◽  
Author(s):  
Pascal Turban ◽  
Stéphane Andrieu ◽  
Alberto Tagliaferri ◽  
Céline De Nadai ◽  
Nike Brookes
Keyword(s):  
Electronic Properties ◽  
Growth Process ◽  
Room Temperature ◽  
Molecular Beam ◽  
Magnetic Circular Dichroism ◽  
Growth Conditions ◽  
Photoemission Spectroscopy ◽  
Structural Quality ◽  
X Ray

ABSTRACTIn this paper, the structural, magnetic and electronic properties of single-crystalline NiMnSb thin films grown by molecular beam epitaxy are presented. The growth process and surface morphology were studied by RHEED and STM. The structural quality of the films was investigated by EXAFS and HRTEM. For the optimized growth conditions, the expected NiMnSb C1b structure was obtained. Moreover, the most stable surface was found to be 4x1 reconstructed. The magnetic and electronic properties were studied by X-ray magnetic circular dichroïsm and spin-resolved x-ray photoemission spectroscopy experiments. The magnetization was observed to be essentially due to Mn, in agreement with theory. The surface was not found to be fully polarized but a polarization near 50% at room temperature was observed. Finally, the preparation of fully epitaxial NiMnSb/MgO/NiMnSb(001) trilayers is presented.

Investigation on the crystal growth process of spherical Si single crystals by melting

2009 ◽  
Vol 311 (16) ◽  
pp. 4116-4122 ◽  
Author(s):  
Zhengxin Liu ◽  
Atsushi Masuda ◽  
Michio Kondo
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Growth Process ◽  
Crystal Growth Process

Nucleation and Growth of 3C-SiC Single Crystals from the Vapor Phase

2009 ◽  
Vol 615-617 ◽  
pp. 31-36 ◽  
Author(s):  
Didier Chaussende ◽  
Jessica Eid ◽  
Frédéric Mercier ◽  
Roland Madar ◽  
Michel Pons
Keyword(s):  
Single Crystals ◽  
Vapor Phase ◽  
Future Development ◽  
Growth Process ◽  
Nucleation And Growth ◽  
Structural Quality ◽  
Bulk Growth ◽  
Nucleation Growth

The conditions to succeed in growing 3C-SiC single crystals are first, make available large 3C-SiC seeds and second, develop a suitable growth process. In this paper, we will address those two issues by reviewing the most recent results in the field. Nucleation, growth, structural quality and doping results will be presented. New insights on 3C bulk growth will be discussed with respect to a future development of real bulk 3C-SiC ingots.

CeNi1-xSb1+yBi1-y Phases with ZrCuSiAs-type and CeNi1.26Sb2 with CaBe2Ge2-type Structure

2014 ◽  
Vol 69 (4) ◽  
pp. 409-416 ◽  
Author(s):  
Konrad Schäfer ◽  
Birgit Gerke ◽  
Oliver Niehaus ◽  
Rainer Pöttgen
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Solid Solutions ◽  
Small Difference ◽  
Magnetic Ordering ◽  
X Ray Diffraction ◽  
X Ray ◽  
By Products ◽  
Experimental Magnetic Moment ◽  
Growth Experiments

Block- and platelet-shaped single crystals of several CeNi1-xSb1+yBi1-y phases with ZrCuSiAstype structure (space group P4=nmm) were grown from a CeNiSb precursor in bismuth fluxes. The structures of CeNiSb1.19Bi0.81, CeNi0.80Sb1.16Bi0.84 and CeNi0.75Sb1.74Bi0.26 were refined from single-crystal X-ray diffractometer data. The 2b nickel site can be fully or partially occupied, and the bismuth square nets show solid solutions with antimony. CaBe2Ge2-type CeNi2-xSb2 crystals occur as by-products of the crystal growth experiments. The structure of a CeNi1.26Sb2 crystal has been refined. The small difference of the compositions hamper phase analytical studies by powder X-ray diffraction. A polycrystalline CeNiSbBi sample showed Curie-Weiss behavior with an experimental magnetic moment of 2.56(1) μB per Ce atom, indicating purely trivalent cerium. No magnetic ordering is detected down to 2:5 K. A 121Sb Mössbauer spectrum showed an isomer shift of δ = -8.06(6)mms-1, substantiating the antimonide character.

Modeling of Fluid Flow and Heat Transfer in a Hydrothermal Crystal Growth System: Use of Fluid-Superposed Porous Layer Theory

1999 ◽  
Vol 121 (4) ◽  
pp. 1049-1058 ◽  
Author(s):  
Q.-S. Chen ◽  
V. Prasad ◽  
A. Chatterjee
Keyword(s):  
Heat Transfer ◽  
Crystal Growth ◽  
Porous Layer ◽  
Hydrothermal System ◽  
Growth Process ◽  
Three Dimensional ◽  
Seed Region ◽  
Porous Bed ◽  
Flow And Heat Transfer ◽  
Growth System

Hydrothermal synthesis, which uses aqueous solvents under high pressure and relatively low temperature, is an important technique for difficult to grow crystalline materials. It is a replica of crystal growth under geological conditions. A hydrothermal growth system usually consists of finely divided particles of the nutrient, predetermined volume of a solvent and a suitably oriented crystal seed (Fig. 1) under very high pressures, generally several thousand bar. The nutrient dissolves at a higher temperature in the lower region, moves to the upper region due to buoyancy-induced convective flows, and deposits on the seed due to lower solubility if the seed region is maintained at a lower temperature. The system can be modeled as a composite fluid and porous layer using the Darcy-Brinkman-Forchheimer flow model in the porous bed. Since the growth process is very slow, the process is considered quasi-steady and the effect of dissolution and growth is neglected. This first study on transport phenomena in a hydrothermal system therefore focuses on the flow and temperature fields without the presence of the seed and mass transfer. A three-dimensional algorithm is used to simulate the flow and heat transfer in a typical autoclave system. An axisymmetric flow pattern at low Grashof numbers becomes three-dimensional at high Grashof numbers. A reduction in the porous bed height for fixed heated and cooled regions can result in oscillatory flows. These results, for the first time, depict the possible flow patterns in a hydrothermal system, that can have far reaching consequences on the growth process and crystal quality.

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