Theory Of Single Crystal Growth Research Articles

Fast growth of cerium-doped lutetium yttrium orthosilicate single crystals and their scintillation properties

The growth of high-quality and large-size cerium-doped lutetium yttrium orthosilicate (Ce:(LuY)2SiO5, Ce:LYSO) crystals with lower cost has great influence on their applications in various physical devices. According to the chemical bonding theory of single crystal growth, the fast thermodynamic growth direction of Ce:LYSO is [010] direction. In this work, the maximum pulling rate of 3.5 mm/h is obtained along [010] direction of Ce:LYSO via the Czochralski (Cz) method. Finally, Ce:LYSO bulk single crystals with diameter of 64 mm and length of 220 mm and mass of 4.2 kg are grown. The luminescence performance of low-doped Ce:LYSO for nuclear irradiation (22Na) detector device was studied. Light yield of 26193 ph/MeV and decay time of 38 ns are obtained. The present work provides a promising fast growth approach to achieving large size functional bulk crystal via both thermodynamic and kinetic controls.

Chemical bonding theory of single crystal growth and its application to fast single crystal growth of rare earth inorganic materials

Fast growth of rare earth single crystals with high melting point can effectively reduce the cost of crystal growth. However, too fast growth rate will cause supercooling upon the melt interface, which will result in a series of quality problems such as cracking. In this paper, the crystal growth process is studied from the perspective of chemical bonding at the growing interface. Combining the potential variations of crystal constituents and the coupling of chemical reaction and diffusion at the growing interface, we demonstrate that both crystallization thermodynamics and kinetics coordinately control the chemical bonding process and enhance the dominant role of chemical bonding architectures at the growing interface during crystal growth. In addition, the bonding characteristics of rare earth ions are further studied in the view of the orbital hybridization, which is useful to study the chemical bonding architecture of rare earth ions at the growing interface. For large-size rare earth oxide single crystals, the optimized crystal growth parameters can be designed on the basis of chemical bonding theory of single crystal growth. These growth parameters promote the anisotropic crystal thermodynamic expression and the isotropic crystal kinetic expression that are controlled in different scales, and help to realize the fast growth of large-size rare earth single crystals with high quality.

Melilite-Type Oxide SrGdGa3O7: Bulk Crystal Growth and Theoretical Studies upon Both Chemical Bonding Theory of Single Crystal Growth and DFT Methods

The chemical bonding theory of single crystal growth has been applied to the SrGdGa3O7 (SGGM) Czochralski growth system, and the optimized growth parameters were calculated. These optimized growth parameters were applied to the Czochralski growth system of SGGM, and the bulk crystal with dimensions of Φ 35 × 150 mm was obtained successfully. The crystal structure of SGGM was demonstrated. The theoretical calculations based on density functional theory methods were carried out on an SGGM crystal. Its band structure and density of state were presented. The present work deepens our understanding of the mesoscale process in the SGGM Czochralski growth system and the structures of an SGGM crystal. It can be concluded that this crystal is a good candidate for all-solid-laser host material.

Chemical bonding theory of single crystal growth and its application to crystal growth and design

The effects of crystallization on the formation of geochemical, biological, and synthetic materials have been motivating decades of research into crystal nucleation and growth processes. The development of crystal growth theories and models can deepen the understanding of physicochemical interactions during the crystal growth process, which facilitates the designing of crystallization approaches in material production. The chemical bonding theory of single crystal growth emphasizes the dominant role of dynamic chemical bonding mechanisms at the growing interfaces. In this paper, we highlight the chemical bonding theory of single crystal growth from the chemical reaction viewpoint, by focusing on the atomic level of the growing interface between the liquid and crystal phases. Using ZnO, CeO2, MnO2 and Y3Al5O12 as examples, we review some typical applications of the chemical bonding theory of single crystal growth in calculating crystal habits, evaluating crystal properties, and guiding practical single crystal growth. Microscopically speaking, the essence of crystal growth and design is to create ideal chemical bonding architectures at both the crystal surface and the growing interface via both thermodynamic and kinetic strategies.

Applying the chemical bonding theory of single crystal growth to a Gd3Ga5O12Czochralski growth system: both thermodynamic and kinetic controls of the mesoscale process during single crystal growth

The chemical bonding theory of single crystal growth was applied to a Gd3Ga5O12 (GGG) Czochralski growth system. On the basis of anisotropic chemical bonding characteristics, the mesoscale process controlled by both thermodynamics and kinetics has been studied in GGG single crystal growth. Starting from the unit-scale in the growth system, the mesoscale structures undergo evolution from GdO8, GaO6, and GaO4 to Gd3Ga5O12 clusters and to a GGG single crystal via chemical bonding between Gd, Ga, and O. On the basis of the chemical bonding theory of single crystals, the GGG single crystal thermodynamically prefers to exhibit a hexagonal configuration along the [111] pulling direction. Kinetically, isotropic mass transfer in the Czochralski growth process leads to formation of a GGG single crystal with a circular configuration, as viewed down along the [111] direction. In such a case, the GGG single crystal maintains the lowest energy. In order to satisfy both thermodynamic and kinetic controls, the thermodynamically preferred {−110} microfacets are exposed on the microscale and the single crystal adopts a circular shape on the macroscale. The present work deepens our understanding of the mesoscale process in the GGG Czochralski growth system.

Morphology engineering of high performance binary oxide electrodes.

Advances in materials have preceded almost every major technological leap since the beginning of civilization. On the nanoscale and microscale, mastery over the morphology, size, and structure of a material enables control of its properties and enhancement of its usefulness for a given application, such as energy storage. In this review paper, our aim is to present a review of morphology engineering of high performance oxide electrode materials for electrochemical energy storage. We begin with the chemical bonding theory of single crystal growth to direct the growth of morphology-controllable materials. We then focus on the growth of various morphologies of binary oxides and their electrochemical performances for lithium ion batteries and supercapacitors. The morphology-performance relationships are elaborated by selecting examples in which there is already reasonable understanding for this relationship. Based on these comprehensive analyses, we proposed colloidal supercapacitor systems beyond morphology control on the basis of system- and ion-level design. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Study on the crystallization process of function inorganic crystal materials

Functional crystal materials used as the important conversion media of light, sound and electricity, have been widely applied to high-tech fields such as energy, information, aerospace and related hot topics at the forefront of materials science and engineering subject. Crystallization process is the core of the preparation of functional materials, crystal growth habit of materials directly affects the functional performances of optical, electrical, magnetic, and catalytic behaviors. During the crystallization process of inorganic materials, crystals are microscopically transformed from free-state ions into the crystalline solid-phase. We can use the ionic electronegativity and microscopic symmetry changes of constituent components, to study the crystallization process of aggregation formation and structure evolution. Using molecular vibration spectroscopy we can at the molecular scale, reveal the crystallization process of nonlinear optical crystal materials in aqueous solution crystallization process, to overcome the lack of traditional means of in situ observations determining those non-long-range order structures. Chemical bonding theory of single crystal growth can from both thermodynamic and kinetic aspects of the whole system, effectively guide the growth of large crystals, reasonably regulate the growth surface and interface thermodynamics and kinetics. The chemical bonding theory of single crystal growth is applied to the design and optimization of growth parameters of large-size crystal pulling growth system, we have built up a large-size crystal growth system, and successfully grown o 2 sapphire crystals, o 3 YAG crystals, and o 4 lithium niobate crystals.

Crystal Growth and Design of Sapphire: Experimental and Calculation Studies of Anisotropic Crystal Growth upon Pulling Directions

The anisotropic growth of large-size sapphire single crystals along different pulling directions was studied on the basis of the chemical bonding theory of single crystal growth and practical Czochralski growth. The projection of thermodynamic morphology of sapphire single crystal respectively along [210], [110], [001], and [001] rotated 57.62° directions can be used to confirm the growth directions of surfaces that are preferred to be exposed thermodynamically in Czochralski growth. Starting from these thermodynamically preferred directions, the possible radial directions that are normal to the four typical pulling directions by kinetic controls have been identified by anisotropic chemical bonding distributions of sapphire single crystal. Chemical bonding calculations demonstrate that the lower pulling rate should be designed when Raxial/Rradial > 1, whereas the higher pulling rate should be designed when Raxial/Rradial < 1. The anisotropic chemical bonding conditions demonstrate the lowest chemical bonding density along the radial directions of sapphire single crystal when it grows along the [001] pulling direction. Taking [001] as the pulling direction in practical growth, a ϕ 2″ sapphire single crystal was grown via the Czochralski method with a growth rate of 2–3 mm/h. Our present work shows the effect of anisotropy on the Czochralski growth of large-size single crystals, which can provide a theoretical guide in practical growth from both thermodynamic and kinetic viewpoints.

Crystallization behaviors of KDP and ADP

Crystallographically, KDP and ADP have familiar (H2PO4-)n framework, which is formed via hydrogen bonding between H2PO4- groups along main crystallographic axes. The common characteristics of both KDP and ADP crystallization behaviours are studied from the viewpoint of (H2PO4-)n framework. On the basis of chemical bonding theory of single crystal growth, the anisotropic hydrogen bonding in (H2PO4-)n framework and the chemical bonding between K+/NH4+ and (H2PO4-)n dominate the anisotropic thermodynamic equilibrium morphology of KDP and ADP. The thermodynamic equilibrium morphology is used to find out the possible preferential growth directions for the dendrite growth of both KDP and ADP, i.e., 〈100〉 and 〈101〉 directions. IR spectroscopy of both KDP and ADP solutions with different concentrations has testified our theoretical results, which shows that H2PO4- ions are initially form (H2PO4-)n framework, and then constituent cations inset into the (H2PO4-)n framework during both KDP and ADP crystallization processes. The present work can provide helpful basic information for the study of crystallization of MH2XO4 crystal family.

Chemical bonding theory of single crystal growth and its application to ϕ 3′′ YAG bulk crystal

The growth of YAG bulk crystals was studied using both theoretical calculations based on the anisotropic chemical bonding conditions and practical growth via the Czochralski (Cz) method. The chemical bonding theory of single crystal growth quantitatively describes the anisotropic bonding behaviors of constituent atoms during crystallizing, which can be applied to the thermodynamic growth of YAG single crystals. Both bonding conditions and crystal symmetry determine the projection configuration along the pulling direction and crystal ridges in the crystal shoulder of YAG grown along [111] direction. During Cz growth process of YAG single crystals, the relative low growth rate along directions results in the exposure of surfaces normal to directions. However, the chemical bonding energy density at the intersection of two adjacent growth directions is higher, leading to the exposure of surfaces normal to directions and the truncated-hexagon configuration of YAG along [111] direction. ϕ 3′′ YAG single crystal was successfully grown. Our present work provides a promising approach to achieve controllable growth for functional bulk crystal via both thermodynamic and kinetic controls.

Evolution of interface configuration in sapphire single crystal growth via Czochralski method

The evolution of interface configuration during sapphire crystal growth by Czochralski method was studied on the basis of chemical bonding conditions at crystal/melt interface. On the basis of chemical bonding theory of single crystal growth, when sapphire single crystal was grown along the c axis direction in Czochralski system, crystal/metal interface is composed of six crystallographically equivalent {110} interfaces thermodynamically. With the rotation of sapphire single crystal in the growth process, the interface configuration developed from hexagon to circle due to the appearance of {100} surfaces and {h10} microfacets at the intersection of two adjacent interfaces. The (h10) microfacet is made of (100) and (110) planes. Lower chemical bonding densities at the {100} surfaces and {h10} microfacets relative to that at {110} surfaces thermodynamically drive the formation of round interface configuration in sapphire Czochralski crystal growth along the c axis direction.

Single crystal growth mechanism of sapphire

We studied the single crystal growth mechanism of sapphire on the basis of chemical bonding calculations at growth interface and the growth of bulk crystal by Czochralski method. The high dislocation density of sapphire single crystals originated from octahedral linking of AlO6 octahedra via sharing their common plane in the structure, which results in intrinsic defects in sapphire single crystals. On the basis of chemical bonding theory of single crystal growth, crystal morphology of sapphire was quantitatively calculated by the chemical bonding conditions of different crystal surfaces. Thermodynamically, sapphire single crystal preferred to exhibit rhombohedral polyhedron bounded by six crystallographically equivalent {012} planes. Bulk sapphire single crystal with the size of 55 mm in diameter and 210 mm in length was grown along the c-axis direction via Czochralski method.

Nanoengineering of Cluster Crystallization of ZnO

Nanoengineering of cluster crystallization of ZnO at different growth interfaces was studied by expanding the unit cell dimensions in 3D space. At the crystal growth interface, the chemical bonding between ZnO nanoclusters and the lattice dominates the growth behaviors of ZnO single crystals. On the basis of chemical bonding theory of single crystal growth, ZnO morphologies were quantitatively calculated by the chemical bonding conditions of nanoclusters at different growth interfaces. When the unit cell dimensions of ZnO nanoclusters expand along the a(b) axis, the decreased chemical bonding energy density at (100) interface leads to the preferential growth of ZnO along the c-axis and the morphology evolution from nanorod to nanowire. When the unit cell dimensions of ZnO nanoclusters expand along the c axis, the decreased chemical bonding energy densities at (001) and (00-1) interfaces lead to the preferential growth of ZnO along the a(b)-axis and the morphology evolution from nanorod to nanoplatelete.

CRYSTALLIZATION OF OXIDES AS FUNCTIONAL MATERIALS

Crystallization is essential to the manufacture of functional materials as varies as electronic devices, energy storage and conversion devices, and highly reactive catalysts. As an important part of functional materials, metal oxides possess wide applications and the crystallization of oxide materials has thus received considerable attention from both fundamental and technological perspectives. With particular emphasis on our recent laboratory results, this feature article gives a brief review in the field of crystallization of oxides. On the basis of chemical bonding theory of single crystal growth, we have simulated thermodynamic growth behaviors of various functional oxides such as ZnO , MgO , Cu2O , Nb2O5, V2O5, MnO2, SnO2, NiO , KDP/ADP, LiNbO3, and NaNbO3. Quantitatively analyzing bonding conditions of controllable crystallographic faces enables us to design proper synthesis strategies and optimize growth parameters, consequently obtaining functional oxides with desirable crystallization behaviors.

Crystallization and functionality of inorganic materials

In this article, we briefly summarized our recent work on the studies of crystallization and functionality of inorganic materials. On the basis of the chemical bonding theory of single crystal growth, we can quantitatively simulate Cu2O crystallization processes in solution system. We also kinetically controlled Cu2O crystallization process in the reduction solution route. Lithium ion battery and supercapacitor performances of some oxides such as Co3O4 and MnO2 were shown to elucidate the important effect of crystallization on functionality of inorganic materials. This work encourages us to create novel functionalities through the study of crystallization of inorganic materials, which warrants more chances in the field of functional materials.

CRYSTALLIZATION BEHAVIOR OF MAGNESIUM SALTS: A SUMMARY OF SOME EXPERIMENTAL OBSERVATIONS

Some efficient methods have been developed to chemically prepare some magnesium salt products with multiscale morphologies such as MgCO 3·3 H 2 O and 5 Mg ( OH )2· MgSO 4·2 H 2 O whiskers, Mg 5( CO 3)4( OH )2·4 H 2 O microplates and aggregates, and Mg ( OH )2 plates and spheres. The crystallization processes of the as-prepared products were studied by designing different reaction routes and corresponding growth morphologies. In these solution chemical systems, Mg 2+ cation was found to be easily coordinated by various ligands, and can be easily transformed into various compounds with variable compositions. The current crystallization observations of some magnesium salts can be readily simulated by the chemical bonding theory of single crystal growth. These results can guide the further studies of various magnesium salts with controllable morphologies.