Growth Of Large-size Crystals Research Articles

Theoretical models for large-sized crystal growth

An accurate cross scale model that can effectively transmit information is the key.

Millimeter-Sized Monoisotopic Cubic 10Boron Phosphide

Boron isotope-containing semiconductors with many novel physical properties have attracted extensive research interest in the areas such as device thermal management, optical components, and neutron detection. However, the existence of strong intrinsic covalent bonding leads to the high-temperature and high-pressure growth conditions of the single crystals of B-compound semiconductors, which has been a great bottleneck limiting their development. Here, high-quality monoisotopic cubic 10BP single crystals at a millimeter scale of approximately 1 mm were grown by a multistep ripening method based on the gas–liquid–solid principle for crystal growth. Structural and morphological analyses have shown that the 10BP single crystals prepared by this method possess a single cubic phase and high crystalline quality. The isotopic effect gives rise to the shift of characteristic peaks in the Raman spectrum. Besides, results obtained through reflection spectrum, photoluminescence (PL), and theoretical calculations demonstrate that 10BP is a semiconductor with an indirect band gap beyond 2 eV. All of these findings can prove that the multipart maturation method is a feasible way to synthesize high-quality 10BP single crystals, which provides a novel and competitive route for the study of isotopic c-BP and the growth of large-sized crystals.

Czochralski growth of mixed cubic sesquioxide crystals in the ternary system Lu2O3–Sc2O3–Y2O3

Cubic rare-earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large-size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3–Sc2O3–Y2O3 revealing a large range of compositions with melting temperatures below 2200°C and a minimum of 2053°C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered structure by the conventional Czochralski method from iridium crucibles. An (Er0.07Sc0.50Y0.43)2O3 crystal is successfully grown and characterized with respect to its crystallographic properties as well as its composition, thermal conductivity and optical absorption in the 1 µm range.

Development of large size crystal growth technology of oxide eutectic scintillator and a proto-type Talbot–Lau imaging system

Wafers of Tb-doped GdAlO3/α-Al2O3 eutectic were fabricated by the micro-pulling-down method using an Ir crucible with a 25 × 25 mm2 die. A prototype X-ray phase imaging detector was developed using a CMOS sensor with a fiber optic plate and the eutectic wafer. X-ray spots with an 8.24 μm period were observed using the detector. X-ray phase imaging of a nylon ball with a diameter of 4 mm was also carried out. It was observed that a phase change of approximately 2 μm occurs at the air–nylon interface. This technique of X-ray phase imaging can be realized in the absence of an absorption grating.

A powder method for the high-efficacy evaluation of electro-optic crystals.

The electro-optic crystal holds great promise for extensive applications in optoelectronics and optical communication. However, the discovery of novel electro-optic crystals is sporadic due to the difficulties of large-sized crystal growth for electro-optic coefficient measurement. Herein, to address this issue, a high-efficacy evaluation method using accessible powder samples is proposed in which the second-harmonic-generation effect, infrared reflectance spectrum and Raman spectrum are introduced to predict the magnitude of the electro-optic coefficient. The calculated electro-optic coefficients of numerous reported electro-optic crystals through this approach give universal agreement to the experimental values, evidencing the validity of the strategy. Based on this method, CsLiMoO4 is screened as a novel potential electro-optic crystal and a high-quality crystal is grown by the Czochralski technique for electro-optic coefficient measurement using the half-wave voltage method, the result of which is also comparable to the calculated value. Consequently, the evaluation strategy presented here will pave a new way to explore promising electro-optic crystals efficiently.

Experimental and theoretical studies of the ternary thiophosphate PbPS3 featuring ethane-like [P2S6]4- units.

The ternary thiophosphate PbPS3 was synthesized by a high-temperature solid-state reaction using PbS, P and S. Single-crystal X-ray diffraction analysis reveals that the compound crystallizes in the P21/c space group. It features a three-dimensional structure, which consists of [PbS8] hendecahedra and isolated ethane-like [P2S6]4- units. PbPS3 can be easily obtained by different methods and shows high air stability, which is beneficial to its chemical synthesis and large-sized crystal growth. The crystal structure, optical properties and electronic structure of PbPS3 have been researched by experimental methods and first-principles calculations. The results show that PbPS3 has a moderate bandgap (Eg. exp. = 2.60 eV) and birefringence (Δncal. = 0.094@1064 nm), as well as a wide transparent range. Furthermore, to better understand the origin of the birefringence, structure comparisons and theoretical calculations were carried out. With a relatively high physicochemical stability and easy synthesis, PbPS3 can be expected to be a prospective birefringent material.

Improvement of Growth Interface Stability for 4-Inch Silicon Carbide Crystal Growth in TSSG

The growth interface instability of large-size SiC growth in top-seeded solution growth (TSSG) is a bottleneck for industrial production. The authors have previously simulated the growth of 4-inch SiC crystals and found that the interface instability in TSSG was greatly affected by the flow field. According to our simulation of the flow field, we proposed a new stepped structure that greatly improved the interface stability of large-size crystal growth. This stepped structure provides a good reference for the growth of large-sized SiC crystals by TSSG in the future.

Ba10In6Zn7S10Se16 and Ba10In6Zn7Se26: Two new infrared nonlinear optical materials with T2 super tetrahedron

The mid/far-infrared (MFIR) nonlinear optical (NLO) materials are very important for the development of new laser sources through laser frequency conversion technologies. In this work, two new noncentrosymmetric chalcogenide compounds Ba10In6Zn7S10Se16 (S10Se16) and Ba10In6Zn7Se26 (Se26) were successfully synthesized for MFIR NLO materials. They are composed of T2 super tetrahedron and show excellent comprehensive NLO performance. Their NLO coefficients are approximately 0.7 and 0.8 times of AgGaS2 at 2.05 μm, and both have high laser induced damage threshold (LIDT) about 12.3 and 10.0 times of AgGaS2, respectively. Both compounds show consistent melting characteristics, which is beneficial for the growth of large-size crystals. The band gaps, NLO coefficients, and density of states (DOS) of the crystals are calculated by first principles simulations to study the origination of NLO response, which indicates that the NLO performance of Se26 is mainly derived from tetrahedrons and supertetrahedrons composed of In/Zn and Se.

Growth and Scintillation Properties of Two-Inch-Diameter SrI2(Eu) Single Crystals

The sealed vertical Bridgman (VB) method is the main technique used to grow SrI2(Eu) crystals because SrI2(Eu) is very hygroscopic. In this study, we grew SrI2(Eu) single crystals with two-inch diameters and four-inch lengths using the VB method equipped with a removable chamber. The SrI2(Eu) single crystals were produced by the Liquinert process, which requires careful consideration of the crucible material and growth atmosphere. After a review of available materials, carbon crucibles were selected due to their several advantages over traditional quartz ampules: (1) they are suitable for large size crystal growth due to which they do not require any process for sealing of quartz ampule before the growth; (2) ease in controlling the temperature gradient because carbon crucibles can be heated directly via a high frequency induction heating system; and (3) carbon crucibles can assist in removing oxygen and moisture from the melt. The starting material, seed, and hot zone were prepared inside the glovebox in...

Large size crystal growth and structural, thermal, optical and electrical properties of KCl1−xBrx mixed crystals

Large size and high quality KCl1−xBrx mixed crystals [with x = 0.0 (pure KCl), 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0 (pure KBr)] have been grown with suitable raw material proportion by the melt (Czochralski) method using the miscible alkali halides KCl and KBr. The grown crystals have been characterized by determining their density, refractive index, lattice constant, chemical composition, thermal parameters (Debye-Waller factor, Debye temperature and Debye frequency), optical absorption, micro hardness and electrical parameters (dielectric constant, dielectric loss factor, AC, and DC electrical conductivities and AC, and DC activation energies) through X-ray diffraction, optical, mechanical and electrical (both AC and DC at various temperatures in the range 30–150 °C) measurements. Results obtained in the present study indicate that mixing KCl with KBr leads to significant tuning of thermal, optical, mechanical and electrical properties without disturbing the crystal structure. The dielectric constant is found to increase several times due to mixing and KCl0.5Br0.5 crystal has the maximum value.

Large-Size KCa0.8Sr0.2I3:Eu2+ Crystals: Growth and Characterization of Scintillation Properties

The newly developed KCa0.8Sr0.2I3:Eu2+ scintillator with 2.5% energy resolution at 662 keV shows great potential for use in gamma-ray spectroscopy applications, but progress toward large-size crystal growth has been hindered by cracking and inclusion problems. In this paper, we report a detailed study on the role of process variables of Bridgman growth, including grain selector designs, ampule surface treatments, and temperature gradients. It was found that crystal cracking can be effectively prevented by using a carbon-coated quartz ampule with a bent capillary. A high temperature gradient of 45 °C/cm at the solid–liquid interface can positively contribute to the suppression of the formation of visible inclusions caused by constitutional supercooling. By using optimized growth parameters, high quality 22 mm diameter KCa0.8Sr0.2I3 single crystals doped with 0.5, 1, and 3 mol % Eu2+ and 38 mm diameter KCa0.8Sr0.2I3 single crystals doped with 0.5 mol % Eu2+ were grown by the Bridgman method. The scintillati...

Crystal Growth, HOMO–LUMO Engineering, and Charge Transfer Degree in Perylene-FxTCNQ (x = 1, 2, 4) Organic Charge Transfer Binary Compounds

The methodologies of searching for novel organic charge transfer binary compounds and large-size crystal growth, in the case that only the two starting organic substances are known but the phase diagram is not known, the thermodynamic data of the binary compound are not known, and even the existence of new binary compounds is not known, were studied. Centimeter-long crystals of novel perylene-F1TCNQ, perylene-F2TCNQ, and perylene-F4TCNQ charge transfer binary compounds are obtained from the gas phase. Kinetically lowering the sublimation rate is the key factor for growing large-size charge transfer compound single crystals. Changing the number of fluorine atoms in FxTCNQ results in the variation of the electron affinity, which further changes the HOMO–LUMO of acceptor. Charge transfer degree is increased with increasing of fluorine atoms in the perylene-FxTCNQ system. Therefore, the structure, stoichiometry, and kind of donor and acceptor enable HOMO–LUMO engineering of the charge transfer compound and tu...

Nucleation kinetics, growth and characterization of sodium tetraborate decahydrate – second harmonic generation in centrosymmetric crystal

Sodium tetraborate decahydrate single crystals were grown from aqueous solution by slow cooling technique. Nucleation and growth kinetics give valuable information about the crystal growth process, which can be utilized in the growth of large size crystals. Attempt are made to study the nucleation parameters such as solubility, induction period, interfacial tension, Gibbs critical free energy, radius of critical nuclei. The crystal possess positive temperature coefficient of solubility. XRD analysis shows that the crystal crystallizes in monoclinic system with space group C2/c. Thermal stability of the crystal was analyzed by TGA/DTG. From optical studies band gap of the material was found to be 5.64 eV. The existence of SHG was confirmed by Q-switched Nd:YAG laser technique.

Pressure-Induced Oriented Attachment Growth of Large-Size Crystals for Constructing 3D Ordered Superstructures.

Oriented attachment (OA), a nonclassical crystal growth mechanism, provides a powerful bottom-up approach to obtain ordered superstructures, which also demonstrate exciting charge transmission characteristic. However, there is little work observably pronouncing the achievement of 3D OA growth of crystallites with large size (e.g., submicrometer crystals). Here, we report that SnO2 3D ordered superstructures can be synthesized by means of a self-limited assembly assisted by OA in a designed high-pressure solvothermal system. The size of primary building blocks is 200-250 nm, which is significantly larger than that in previous results (normally <10 nm). High pressure plays the key role in the formation of 3D configuration and fusion of adjacent crystals. Furthermore, this high-pressure strategy can be readily expanded to additional materials. We anticipate that the welded structures will constitute an ideal system with relevance to applications in optical responses, lithium ion battery, solar cells, and chemical sensing.

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.

Nucleation kinetics and growth aspects of negative solubility lithium sulphate monohydrate single crystal

Nucleation and growth kinetics give valuable information about the crystal growth process, which can be employed in the growth of large size crystals. Accordingly, this paper discusses nucleation theory as applied to crystallizing negative solubility lithium sulphate monohydrate (LSMH) crystal. Solubility, metastable zone and induction period values were determined experimentally in order to optimize the growth parameters. The nucleation parameters such as interfacial energy, volume free energy, critical free energy and critical radius have been evaluated. The results have been discussed in detail. The good quality single crystal of LSMH was grown by the low temperature solution growth technique. The growth and dislocation behaviors were detected under the etching studies. It is shown that the classical approach explains the available nucleation data under most conditions used for growing LSMH crystals.

Review of some Aspects of Single Crystal Growth Using Czochralski Crystal Growth Technique

Abstract Single crystal that semiconductor industry thrive on, are grown using Czochralski (CZ) crystal growth technique. Over the years many researchers have investigated the problems related to CZ crystal growth system and number of studies related to different aspects of CZ crystal growth is available in open literature. Some of the important aspects related to Czochralski (CZ) crystal growth system used for growing single crystal are discussed. Origin of melt convection due to buoyant forces, forced convection due to crystal and crucible rotation and Marangoni convection due to thermo-capillary forces, and their effect on heat and species transport phenomena in the melt pool has been reviewed. Flow in present day large size crystal growth using CZ crystal growth system becomes oscillatory. Oscillations in melt can be damped using externally applied magnetic field. Effect of axial, transverse and inhomogeneous (CUSP) magnetic field on different melt convection has been a subject of interest for various research efforts. Oxygen release from silica crucible during growth of silicon crystal and mechanism for its incorporation into the growing crystal has also been reviewed. Conditions leading to growth of low oxygen concentration silicon crystal are elaborated.

Nucleation kinetics, growth, mechanical, thermal and optical characterization of sulphamic acid single crystal

Sulphamic acid (HSO3NH2) is a potential material that exhibits excellent piezoelectric and non-linear optical properties. Nucleation and growth kinetics give valuable information about the crystal growth process, which can be employed in the growth of large size crystals. Thus we have studied its nucleation parameters such as solubility, metastable zone width, induction period, interfacial tension, critical free energy, volume free energy change, critical nucleus and found that good quality sulphamic acid crystal can be grown at low temperature. Growth of good quality crystal was done by adopting slow evaporation solution growth technique at room temperature and as a result, good quality single crystal was grown. The grown bulk single crystal of the title compound was subjected to various characterization analyses. Its unit cell dimensions were confirmed using powder X-ray diffraction. Further its crystalline perfection was assessed using high resolution X-ray diffraction and X-ray topography techniques and it was found that it is reasonably good. Its various functional groups were identified from the Fourier transform-Raman method. Nanoindentation was performed to identify the load dependence and independence of hardness (H) and Young's modulus (E) using the Oliver–Pharr method and it was found that both H and E exhibit peak load dependence. Photopyroelectric study was performed to identify its thermal properties such as thermal diffusivity (α), thermal conductivity (k), thermal effusivity (e), and heat capacity (cp). These studies reveal that it has high thermal stability compared to other single crystals. The optical homogeneity of the grown crystal was assessed using a birefringence interferometer and it was found to be reasonably good.

Study on Ammonium Sulfate Crystallization in the Ammonium Desulphurization Process in a Coal-based Power Plant in the Petrochemical Industry

Ammonium sulfate crystallization of ammonia-based flue gas desulphurization was studied. Experiments were conducted to study the influence of pH, temperature, and the fly ash content of the solution on ammonium sulfate crystallization. The fly ash promoted ammonium sulfate crystallization was investigated as well. The results show that the pH has a significant impact on the mean crystal size and the shape of the ammonium sulfate crystals, and it is appropriate to keep pH at 5.0–5.5. The mean crystal size at a temperature of 60°C is larger than that of 70°C, and it will not change significantly from 70 to 90°C. Appropriate concentration of fly ash is helpful to ammonium sulfate crystallization and fly ash acts as a crystal nucleus, while higher fly ash concentration prevented the growth of large-size crystals and surface absorption becomes obvious. The ideal concentration of fly ash for the largest size crystal is about 4 g/L.

UV laser-induced damage tolerance measurements of CsB 3O 5 crystals and its application for UV light generation

Cesium triborate, CsB 3O 5 (CBO), is an excellent nonlinear optical crystal for ultraviolet light generation. CBO crystals can be grown by top seeded solution growth from self flux solutions. The growth of large-size crystal is difficult because of the multi-nucleation and dissolution of seed during growth. These problems have been avoided and large size crystals (159.2 g) of size 50 × 45 × 45 mm 3 ( a × b × c) have been grown. The bulk laser-induced damage threshold (LIDT) of CBO was determined using an 1-on-1 technique by the third-harmonic (355 nm) light of longitudinal single-mode Q-switch Nd:YAG laser. The bulk LIDT was found to be two times that of fused quartz for a 6 ns pulse. The as-grown CBO crystal has been used to generate the highest ever reported third-harmonic power of 103 W for the case of a single-pass frequency-conversion system using a high-power Nd:YAG laser.