Growth of YFeO3 crystal by edge-defined film-fed growth method

A sizeable single crystal of YFeO₃ (YIP) with the dimensions of 19×15×15 mm³ has been successfully grown by the edge-defined film-fed growth method. Thermal magnetic analysis shows that Curie temperature of as-grown YIP crystal is about 363.5 °C. The hardness of YIP crystal was measured as 900 VDH, equivalent to about 7.1 moh. Moreover, the optical transmittance of as-grown YIP crystal can be significantly enhanced if this crystal was annealed at 700 °C in oxygen atmosphere.     

The growth of controlled profile crystals by Stepanov's method

Single crystals in the shapes of plates, tubes and rods of various cross sections are widely used in many areas of science and technology. Of great importance is the production of such single crystal specimens directly from the melt. By Stepanov's method, the desired shape of the crystal is obtained by the proper selection of a device which shapes the melt column which rises due to the capillary effect. The capillary parameters determine the shape of the profile curve. The thermal parameters, taking into account the equilibrium crystal shape, define the position and shape of the crystallization front. The use of the shaper makes the process self-stabilizing. A negative feedback which damps out perturbations appears in the crystal-melt system and thus permits the production of controlled profile crystals with constant cross-section along their length. Thermoelastic stresses created in ribbons and rods as a result of temperature-induced misfit deformations are considered. The generation of dislocations in crystals occurs mainly due to stresses arising near the crystallization front. Various versions of the method and their applications to some materials are discussed.     

Determination of linear growth rates of crystals (II). The shape factors method

A method using dimensionless shape factors for the determination of linear growth rates of crystals is described. The relevant shape coefficients are assessed on the basis of properly selected linear parameters of the crystal.     

The growth of HgI2 crystals

The paper presents a system for αHgI₂ crystal growth by the temperature oscillation method. The system has a capability of crystal growing at an excess I₂ or Hg vapour pressure. Optimum conditions for producing crystals up to 2 cm³ by volume have been established. The crystals grown at an excess I₂ vapour pressure have higher resistivity and higher drift electron and hole mobilities — μ_e = 120 cm² V⁻¹ s⁻¹ and μ_h = 6 cm² V⁻¹ s⁻¹, respectively.     

Edge-defined film-fed growth of Yb:YVO4 single crystal plates

The applicability of the edge-defined film-fed growth (EFG) technique for Yb_xY_(1−x)VO₄ (x=0.05, 0.1 and 1) was approved by successful growth of crystals up to 80 mm in length as the thin plates. Low-angle grain boundaries and the crystal coloration as main defects were found. Optimal seed orientation was suggested on the strength of vanadate crystal plate morphology. Optical properties, chemical composition and the crystalline quality were investigated.     

Designed additives for controlled growth of crystals of phospholipid interacting proteins: Short chain phospholipids

A new approach to crystallization of proteins that interact with lipids has been applied to the protein crambin. Short chain phospholipids are water-soluble additives and effectively lower the amount of protein needed to form crambin crystals by lowering protein solubility and inhibiting crystal growth in the fastest growing direction. Compared with optimal crystallization conditions without phospholipid, which gave large crambin crystals (1.5 × 0.7 × 0.5 mm), a 30–60-fold decrease in protein concentration as well as 5-fold decrease in volume were achieved. As a result, the efficiency of crystal production was increased by 150–300-fold. The crystals obtained diffracted beyond 1.5 Å resolution. The most effective additive, phosphotidylcholine, had a size comparable to the proposed binding site on crambin and on the homologous membrane-active toxins. The procedure developed may be useful for crystallization of other phospholipid interacting proteins as well as transmembrane proteins.     

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.     

Temperature gradient controlled growth and optical properties of Er:BaY2F8 crystals

Single crystals of Erbium (Er) doped BaY₂F₈ have been obtained by the temperature gradient technique (TGT). No‐seed‐grown crystal of Er:BaY₂F₈, with the dimensions up to several centimeters, was obtained by self‐crystallization. The optimizations of various growth parameters were systemically investigated. The results indicated that the temperature gradient of 6‐7 K/mm and the cooling velocity less than 6 K/h were suitable for the crystal growth. The XRD data and the investigations on the growth striations by a stereo polarization microscope displayed that the [001] direction is the dominating direction for the crystal growth. The crystal grown by TGT often cracks along with the (100) plane, which is caused by the excessive decrease of the temperature during the crystal growth, for there is a rapid change in the thermal expansion curve of the BaY₂F₈ crystal in the temperature range from 800 °C to 900 °C. The spectral properties of Er:BaY₂F₈ single crystals have been studied and the effects of frequency up‐conversion of the crystals are reported. Spectral data suggest that the quality of Er:BaY₂F₈ crystal obtained by TGT method is good and the crystal has the potential application in laser devices. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

On the shape of crystals grown by Kyropoulos technique

The shape of the crystal grown by Kyropoulos technique has been evaluated on the basis of simple mass transfer approach. For some specific cases we have computed the shapes which are resaonable and generally in conformity with physical requirements. To verify the results crystals of KCl were grown under two specific conditions. The shapes of the resulting crystals agreeing with the calculated shapes within limits of error lend support to the validity of mass transfer approach.     

Dendritic growth of snow crystals

The hypothesis that allows the interpretation of dendritic growth of a snow crystal in terms of diffusion-limited aggregation is criticized. The results of simulation of growth of quasi-two-dimensional crystals in two-and three-dimensional media based on the classical two-parametric model of diffusion-limited aggregation are used as an argument in this criticism. It is established that the model dimensionality considerably influences morphology of the grown crystal. The mechanism of dendritic growth of a snow crystal in which the main part is played by the surface processes at the ice/water interface is suggested.     

Iso-epitaxial growth of n-octacosane crystals

Iso-epitaxial(epilayer)growth of n-octacosane crystals is reported. The morphology of the epilayers is in the form of triangular growth islands with or without truncature. Epilayer growth precedes spiral growth mechanism which occurs at medium and low supersaturations, respectively. The occurrence of triangular and truncated rhombic platelets is found to be a manifestation of growth at medium supersaturations.     

Solid-phase growth of CuGaS2 crystals

Homogenized mixtures of copper, gallium, and sulphur were annealed for 200 hrs. under vacuum at about 1000–1050°C (i.e. below the melting point of the CuGaS₂ phase) in quartz ampoules in a vertical position, and then cooled down in a temperature gradient. The final charge was made up of three well-defined portions: a yellow polycrystalline CuGaS₂ with large blocks of CuGaS₂ (close to stoichiometry), a black portion with darkgreen aggregates of small CuGaS₂ crystals, and yellow laminae of CuGaS₂ single crystals, slightly inclined away from [112] direction. — A coupled growth mechanism — solidstate-diffusion-assisted coalescence/vapour transport — is assumed.     

Spiral growth of potassium bichromate crystals

Some observations of growth spirals and hillocks on {001} surfaces of potassium bichromate crystals grown from aqueous solutions are presented and discussed. It is shown that a spiral pattern in fact represents a macrospiral developed as a result of the cooperative action of a group of dislocations.     

Dendritic growth forms of borax crystals

A variety of dendritic forms of borax grown from solutions by the film formation method is given. The changing growth morphology is followed as a function of concentration and temperature. The initial, intermediate and final growth morphologies are described and discussed. Influence of evaporation rate and supersaturation on the mechanism of growth is assessed. It is suggested that under all crystallization conditions, borax crystals have dendritic form in the initial stages of growth.     

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.     

On the shape of the phase boundary of melt-grown ribbon-shaped crystals

Approximated analytical solution of the stationary Stefan problem for the ribbon crystals pulled from the melt are obtained. The results of calculation of the crystallization front are compared with the numerical solution obtained by finite elements method. The good coincidance is demonstrated.     

The inhibitory growth mechanism of saccharides on the growth of ice crystals from aqueous solutions

The inhibitory growth mechanism controlling the growth of ice crystals due to the presence of saccharides, as in plant cells, was experimentally studied at low temperature. As a result, it was found that the growth rate of ice crystals in saccharide solutions depended on the type and concentration of the saccharides. The experimental facts can be explained by the concept that giant hydrated clusters of saccharides create the framework that causes a resistance to the volume diffusion of water molecules.