Journal of Crystal Growth最新文献

The growth of high-quality large-sized KDP crystals is to meet the requirements of high-power laser systems. The convective transport characteristics of KDP solution are one of the key factors affecting the growth of large-sized KDP crystals in the growth vessel. In this work, the three-dimensional simulation of flow and mass transfer occurring in the process of large-sized cuboid potassium dihydrogen phosphate (KDP) grown by the long seed limitation method (LSLM) has been performed employing the finite element method. The standard k-ε model with the enhanced wall treatment is used to calculate the turbulence flow in the growth vessel. The temporal and spatial evolution of flow field near the crystal face and supersaturation field on the crystal face during the growth is discussed in detail. The time-averaged supersaturation field on the crystal face at various factors is analyzed. The relative strengths of natural and forced convections on different conditions is compared, the convective mass transfer regime at different conditions is revealed.

R₃Fe₅O₁₂ (RIG) crystals are the most desirable elements for magneto-optical isolators in the near-infrared (NIR) to mid-infrared (MIR) region, with ever-growing demands for optical fiber communication and high-power laser system. Now, this system is the only commercialized Faraday rotator for optical isolators in 5G wireless communications. However, the growth of high-quality bulk RIG single crystals has been a big challenge for a long time, due to the typical incongruent melting characteristic and complex phase relationships. This work comprehensively summarizes the recent advances for the growth of RIG single crystals, including the proper choice of flux and innovative strategies on several growth techniques, like the flux-Bridgman, edge-defined film-fed growth (EFG) and top seeded solution growth (TSSG), etc. Effective modulation on the optical and magneto-optical performance is highlighted. Some ongoing perspectives are also proposed and discussed. It is anticipated that this work will provide deeper insight into the exploration of high-performance magneto-optical crystals for potential applications in NIR-MIR wavelength.

In materials science, selecting the right synthesis technique for specific compounds is one of the most important steps. High-pressure conditions have a significant effect on the crystal growth processes, leading to the creation of unique structures and properties that usually are not possible under normal conditions. The prime objective of this article is to illustrate the benefits of using high-pressure, high-temperature (HPHT) technique when developing two-dimensional (2D) materials. We could successfully grow bulk single crystals of hexagonal boron nitride (hBN) and magnesium doped hexagonal boron nitride (Mg-hBN) from Mg-B-N solvent. Further exploration of the Mg-B-N system could lead to the crystallization of isotopically ¹⁰B and ¹¹B enriched hBN crystals, and other doped variants of it. Black phosphorus (b-P) and black phosphorus doped with arsenic (b-AsP) were obtained by directly converting its elements into melt and subsequently crystallizing them under HPHT. Germanium arsenide (GeAs) bulk single crystals were also obtained from the melt at a pressure of 1 GPa. Upon crystallization, all these compounds exhibit the anticipated layered structures, which makes them easy to exfoliate into 2D flakes, thus providing opportunities to modify their electrical behavior and create new useful devices.

Today Li-ion battery recycling processes allow the recovery of heavy metal elements such as copper, cobalt, nickel and manganese. On the other hand, lithium is generally lost in slag or released to the environment and therefore is not recovered. Lithium is an element non-substitutable of Li-ion batteries which technology is indispensable in electromobility and energy transition. Moreover, since 2020 the EU has classified lithium as a “critical metal”.

The objective of this work is to develop a precipitation process of lithium salts from spent Li-ion batteries (LIBs), which respects the environment, consumes little energy and material, by maximizing the yield and purity of the product obtained. Experimental procedures in batch and continuous reactors made possible to optimize operating parameters such as temperature, solid concentration inside the reactor, reaction time and stirring speed.

Lithium carbonate and lithium hydroxide are the preferred precursors for synthetizing LIBs since they deliver high purity in the final product, and the most important are cost effective. Shin e al. (2022) [1] In this work the precipitation of Li₂CO₃ is performed. Lithium carbonate exhibits inverse solubility thus, the more the temperature increases, the residual content of dissolved lithium decreases and therefore the quantity of precipitated lithium carbonate increases. From the experiments a suitable set-up of the process is presented as well as a novel route for the precipitation of lithium salts by direct carbonation. This allows to improve the purity and yield of the precipitate.

Doped semiconductor crystals of solid solution Cd_1-xMn_xTe:Fe²⁺ were grown by the high-pressure Bridgman method, covering the range of their existence as a zinc blende structure (0 < x < 0.76). The concentration of the Fe²⁺ impurities was approximately 10⁻³ wt% in all the studied samples. The structural and optical properties of the crystals were investigated, including the case of high concentrations of x  > 0.4. The correlations between the composition of solid solution crystals of Cd_1-xMn_xTe:Fe²⁺, the lattice constant, the band gap, and the maxima positions of the Fe²⁺ active ion absorption and emission spectra were found experimentally and explained physically. A theoretical model based on the principle of compositional additivity for solid solution semiconductor materials was first used for explaining the long-wavelength sin-band linear “redshift” of absorption and emission bands in the spectra of Cd_1-xMn_xTe:Fe²⁺ crystals with increasing solid solution concentration. A new effect is discovered for the differentiated redshift of the Jahn-Teller components (bands) of the total absorption spectrum. Longwavelength absorption bands have a stronger redshift than shortwavelength absorption bands. The redshifts in the maxima of the total absorption and emission spectra have shift (slope) coefficients K_ab ≈ 1.7 nm /at.% and K_em ≈ 6.1 nm /at.%, respectively. The obtained results can be used to predict and design laser media based on Cd_1-xMn_xTe:Fe²⁺ solid solution crystals while controlling the lasing range (for all Mn concentrations).

The purpose of this study was to examine crystallization of ferritin on some biocompatible materials, like bare Ti, and Ti substrate covered by polypyrrole (PPy) through electrochemical polymerization.

Crystallization process is known to be dependent on the way of crystal nucleation – homogenous or heterogeneous. On the other hand, heterogeneous formation of nuclei also depends on the substrate interacting with the crystallizing molecule such reducing the energy of nucleation. Here we report a study of the crystallization of ferritin on bare Ti, Ti covered by polypyrrole (PPy) film through elecropolymerisation, Ti with electrodeposited ferritin on its surface, as well as Ti with ferritin adhered through steeping.

Studies of crystallization have been performed in conditions of vapor diffusion mode, applying hanging and sitting drop versions. Results obtained show that crystallization on a bare Ti surface do not happen for a very long time and crystals become visible after a month, while on a glass surface they are detectable in a week. In case the Ti is covered by ferritin molecules, crystallization happens and crystal morphology depends on the way of ferritin layer has been deposited on the Ti substrate. Crystallization of ferritin on PPy has been found only in case of porous coverage and also mainly in hanging drop experiments.

Atomic force microscopy experiments with modelling nature-like factors affecting crystal-genetic processes registered phenomena accompanying continuous transition from dissolution to growth (through the saturation point) on one and the same defect in a molecular hydroxymethylquinoxalinedioxide (C₁₀H₁₀N₂O₄) crystal. The conducted analysis of the mechanisms of attachment/detachment of the matter to the crystal, the calculations of nanoscale kinetic parameters and their further statistic processing allowed us to gain insights into the fundamental problem of reversibility of growth and dissolution. The findings will contribute to understanding of the theory of crystal-forming processes occurring near equilibrium and to interpretation of pictures of zoning in nature crystals.

We have studied the structural and morphological features of SnSe₂ films grown on Si(111) and Bi₂Se₃(0001) surfaces in an in situ reflection electron microscope. On both substrates, the SnSe₂ growth started at 100 °C as an amorphous layer, and when thickness reached 1 nm, crystallized by raising the growth temperature to 250 °C without interruption of Sn and Se fluxes. The introduction of this growth-initiating stage has decreased the concentration of screw dislocations on films’ surfaces to ∼18 and ∼2 μm⁻² for the Si(111) and Bi₂Se₃(0001) substrates, respectively. High-resolution transmission electron microscopy investigation has shown that the layered SnSe₂ film has a hexagonal lattice structure corresponding to the space group $\text{P}\overline{3}\text{m}1$ (no. 164) with lattice parameters a = 0.38 nm and c = 0.62 nm. Raman spectroscopy has shown vibrational modes corresponding to the 1T-SnSe₂ phase. We have shown that the decrease in Se:Sn flux ratio switches growth mode from Frank—van der Merwe type SnSe₂ epitaxy to Volmer—Weber type nucleation of SnSe 3D islands.

Density functional theory was used to analyze the formation of InGaN from trimethyl indium (TMIn) and trimethyl gallium (TMGa) by metalorganic chemical vapor deposition in ammonia in terms of oligomerization reactions of the nitrides and the elimination reactions of the oligomers formed. The reaction pathways were assumed by reference to previous studies, and their free energy and energy barrier characteristics were calculated for different temperatures. The results indicated that, in the oligomerization reactions, the decomposition temperature of dimers is higher than that of trimers; dimethyl indium nitride (DMInNH₂) is more prone to polymerization than dimethyl gallium nitride (DMGaNH₂); and oligomerization of DMInNH₂ is more likely to occur. In the elimination reactions, when the reaction temperature is high, oligomers tend to generate [MMXNH₂][MMXNH₂] (MM = monomethyl; X  = In or Ga) first by intramolecular elimination, and then generate the stable products [XNHNH₂][XNHNH₂] by intermolecular elimination of NH₃. However, when the reaction temperature is low, [X(NH₂)₃][X(NH₂)₃] is generated by intermolecular elimination.

Indium selenide (In_xSe_y), group III-VI semiconductor, has various crystal phases, so that the growth technique for controlling the crystal phase is necessary for studying the novel properties as well as the device applications. In this work, we demonstrate the phase-controlled growth of In_xSe_y using metalorganic chemical vapor deposition. As the growth temperature increases, the crystal phase changes from InSe, β-In₂Se₃ to γ-In₂Se₃, which can be explained by their thermal stability. Besides, as the gas-phase VI/III source molar ratio increases, the crystal phase changes from InSe to In₂Se₃, indicating that Se-rich surface stoichiometry results in Se-rich crystal phase, i.e. In₂Se₃. We summarized the crystal phases depending on the growth temperature and the VI/III source molar ratio as a phase diagram. The In_xSe_y growth near the phase boundary between InSe and β-In₂Se₃ take place under surface-reaction-limited regime and the dissociation of Se source mainly controls the surface stoichiometry. This phase diagram will be a guideline for the phase-pure In_xSe_y synthesis and pave the way for the optoelectronic applications.