Efficient conditions for the growth of MoO3 single crystals under oxygen atomsphere

Single crystals of MoO₃ have been grown under an oxygen atmosphere using a horizontal tubular furnace. The temperature and pressure necessary to grow satisfactory crystals in oxygen along [100] and [010] directions are determined.     

Growth of p-type InP single crystals by the temperature gradient method

P-type InP single crystals doped with zinc or cadmium have been prepared from a solution using indium as a solvent in which a temperature gradient was maintained for the transport of the InP solute. The average growth rate was between 1.1 and 3.0 mm/week. The room temperature hole concentration of the crystals obtained was in a range of 10¹⁷ to 10¹⁸ cm^-3. The distribution coefficients of zinc and cadmium were 0.8 and 0.004, respectively. The temperature gradient method makes it possible to dope the crystals with volatile impurities in a controlled manner.     

Growth of Sb-Bi gradient single crystals

The growth conditions and structural quality of Sb-Bi gradient single crystals with Bi content from 2 to 18 at %, grown by the Czochralski method with solid phase feed, are investigated. Bi distribution in the crystals along their pulling direction are studied by electron probe microanalysis and the change in the interplanar spacing is analyzed by double-crystal X-ray diffraction. It is established that the pulling rate and feed mass affect the Bi distribution in Sb-Bi single crystals.     

Growth of magnetic garnet single crystals from high temperature solution

A review is given to show the development of growth techniques for single crystals for the incongruently melting yttrium iron garnet. As a result of this world-wide development a technique is described in some detail which allows well controlled nucleation and growth using a high temperature solution.     

The growth and mechanical properties of paratellurite single crystals at high temperatures

α-TeO₂ single crystals have been grown by the Czochralski method on specially developed systems with automatic growth control. The mechanical properties of crystals under compression in the [100], [110], and [221] directions at a constant strain rate of about 10⁻⁴ s⁻¹ in the temperature range T = 733−993 K have been investigated. The distribution of plastic shear strain in deformed samples is has been experimentally studied. Manifestations of localized strain in covalent paratellurite crystals at T > 900 K are revealed for the first time. The active slip systems along which localized shear band are oriented are determined. The temperature dependence of the critical stress of transition to localized flow is investigated.     

Bulk GaN single crystals: growth conditions by flux method

Hexagonal GaN platelet crystals with a size of 1–4 mm have been grown by a Li-based flux method. The influence of growth conditions such as the molar ratio of starting materials, temperature, pressure, the position of Li₃N in the crucible on the growth of GaN single crystals was studied. The quality of GaN single crystal was checked by optical microscope and X-ray rocking curve.     

Growth of KDP single crystals by temperature reduction under diffusion transport

Growth rates of 37 μm/hour for {010} faces and 40 μm/hour for [001] directions have been found for KDP crystals growing in gelled media by temperature reduction. These values, higher than those recorded in alcohol-diffusing techniques are in the range of more classical methods. A device for obtaining larger crystal size is also described.     

Solution growth of new ferroelectric glycine phosphite unidirectional single crystals at room temperature

Glycine phosphite [NH₃CH₂COOH₃PO₃], abbreviated as GPI is the second hydrogen bonded ferroelectric crystal combination of phosphorous acid and amino acid following βnine phosphite crystals abbreviated as BPI. Sankaranarayanan and Ramasamy‐Technique was adopted to prepare the ferroelectric glycine phosphite unidirectional single crystal. The growth orientation was imposed by the pre‐grown 〈010〉 seed. As water was the solvent, transparent, colourless crystal with cylindrical shaped ingot of sized 20mm‐diameter was grown. Powder X‐ray diffraction, HRXRD, FTIR, dielectric and mechanical studies were carried out. The results are discussed in detail. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of NiAl shape memory alloy single crystals

As a potential candidate of high temperature Shape Memory Alloy (SMA), inter metallic compound NiAl has been studied for more than 30 years. In order to understand better the mechanism of the Shape Memory Effect(SME) in β -NiAl phase, its bulk single crystal have been prepared with an improved magnetic levitation cold crucible Czoehralski(CZ) technique in our lab. The crystal growth procedure and the β -NiAl phase stability are discussed in this paper.     

Study of the possibility of growing germanium single crystals under low temperature gradients

The possibility of growing germanium single crystals under low temperature gradients in order to produce a dislocation-free material has been studied. Germanium crystals with a dislocation density of about 100–200 cm^?2 have been grown in a system with a weight control of crystal growth at maximum axial gradients of about 1.5 K/cm.     

The melt growth of oxide and related single crystals

This article reviews the principle changes which have occured during the last three years in the techniques used to produce single crystals of oxide and similar single crystals from the melt. The technological demands created by device applications are emphasized and the current state of knowledge upon the major crystalline defects is discussed. The role of accurate phase diagram analysis, the importance now attached to the atmosphere in which a crystal grows and the relevance of looking at crystals with greater resolution are stressed particularly.     

Preferred growth of bismuth single crystals

The results of the study of the factors influencing the orientation of the ( 111 ) cleavage plane of bismuth are presented. It has been observed that at high purity the growth rates and temperature gradients do influence the orientation whereas at low purities no such influence is observed.     

A crystallizer for the investigation of conditions of growth of single crystals from solutions

The crystallizer of the Walker-Kohman type for isotherm growing of single crystals from solutions is described which has been designed to provide the maintenance of constant conditions of crystallization chosen in advance and the investigation of the influence of these conditions on the resulting structural regularity of the crystals as grown. The temperature of the solution can be kept inside the interval from 30 to 60°C, with an accuracy ±0.002°C. The equipment allows the setting and keeping the requested value of supersaturation, hydrodynamic conditions, thermal stabilization of the crystallization solution and enables the optic and gravimetric observing of the single crystal during its growth. The total function of the described equipment was tested by growing single crystals of triglycine sulphate at 52°C.     

The growth of ZnWO4 and CdWO4 single crystals from melt by the low thermal gradient Czochralski technique

Crystallography Reports - The features of growth of single crystals of cadmium and zinc tungstates by the low thermal gradient Czochralski technique have been investigated. The effect of change in...     

Effect of the growth rate on thermal conditions during the growth of single crystals with melt feeding

An attempt is made to establish a correlation between the radial and axial growth rates and the change in the conditions of heat transfer from a growing crystal to the atmosphere of the water-cooled vacuum furnace for the growth of large alkali halide single crystals. It is found experimentally that an increase in the growth rate leads to an increase in the automatic compensation of the melt temperature by the main heater. In this case, the thickness of the layer of melt condensate on the end face and the lateral surface of the crystal decreases. It is revealed that the possibility of growing infinitely long ingots in the presence of intense melt evaporation is restricted by the possibilities of the heat transport through the boundary between the furnace atmosphere and the cooled furnace walls, onto which melt condensate deposits.     

Ordering and magnetostriction in Fe alloy single crystals

Short-range and long-range ordering in α-Fe terminal solid solution phase (A2 phase with bcc structure) influences its physical, mechanical, magnetic and magnetostrictive behavior. Single crystal sample forms are ideal for examining order in these alloys using X-ray and neutron scattering techniques. Limited structural information available suggests that the lattice of A2 phase at room temperature contains a mixture of regions with local atomic environments similar to those expected in the long-range ordered structures in stable/metastable equilibrium with the A2 phase. The nature and extent of these regions are sensitive to alloy composition and the thermal history. The lattice strain modulations result from the nature of solute atom distribution (short-range ordering) in each region and impact the physical, mechanical, corrosion and magnetic behaviors. A need for a fundamental understanding of ordering in Fe and other alloys through structural evaluations of local atomic environments in alloy single crystals is suggested in this review.     

Growth rate of single acetaminophen crystals in supersaturated aqueous solution under different operating conditions

Single crystal growth experiments were conducted to investigate the growth rate of acetaminophen (paracetamol) crystals under carefully controlled conditions of temperature, supersaturation and pH value. The relative growth rate of the different faces was studied. Growth Rate Dispersion (GRD) was observed by studying the effect of supersaturation and temperature on the growth rate. The growth rate in all directions was found to be temperature dependant. Elongation of the crystals was measured due to the faster growth in the Y‐ direction and Xa direction compared to in the Xb direction. Dissolution of the crystals was observed at pH values greater than 8.5, and a growth rate retardation was observed when increasing the pH from 5.6, which is the normal value without additions, to higher values in both acidic and basic mediums up to 8.5. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Variation of low temperature internal friction at microplastic deformation of high purity molybdenum single crystals

Amplitude and temperature spectra of ultrasound absorption in weakly deformed high purity molybdenum single crystals of different orientations were measured. The results were discussed in terms of parameter changes related to quasiparticle- or dislocation oscillations, respectively, dislocation-point defect interactions as well as defect generation at microplastic deformation.     

Horizontal bridgman growth of gaas single crystals

In order to meet requirements for the preparation of low dislocation density GaAs single crystals a horizontal Bridgman type apparatus was designed. Construction of the apparatus allows the establishment of enhanced temperature stability of the arsenic source and hence better stability of the arsenic vapour pressure during the growth. This effect was achieved without application of heat pipes which are usually used for the improvement of thermal profile and temperature stability. The influence of different arsenic vapour pressures on the density of dislocations was confirmed in the course of this work.     

Domain structure and dielectric properties of TGS and DTGS single crystals depending on growth conditions

The influence of growth temperature and supersaturation of solution on domain structure and dielectric properties of TGS and DTGS single crystals was investigated. The qualitative and quantitative analysis of domain structures was carried out. The optimal growth conditions were found. It proves to be useful to arrange the measured values in table where lines correspond to growth temperatures and columns – to supersaturations for investigation of optimal growth conditions. The diagonal of extremal values exists in this table. The existence of optimal growth conditions explains in terms of interaction between domain and defect structures.