Journal of Crystal Growth最新文献

Tb_1-xHo_xVO₄ (THV) magneto-optical crystal with diameter of 27 mm and length of 40 mm was grown by the Czochralski (Cz) technique for the first time. The structural perfection of THV crystal was studied by the high-resolution X-ray diffraction rocking curve measurement, proving the high crystallinity quality of THV. THV shows high transmittance of greater than 75 % within the wavelength range of 665–1600 nm. The Verdet constants of THV at 532, 633 and 1064 nm are 370, 226 and 56 rad·m⁻¹T⁻¹, 40 %–95 % higher than these of commercial TGG crystal. Additionally, THV exhibits lower absorption coefficient (0.05 cm⁻¹), higher magneto-optical figure of merit (175 deg/dB) and extinction ratio (43 dB) at 1064 nm compared with TGG. Evaluation of thermal performance and laser-induced damage threshold of THV were also made to promote the potential application in high-power optical isolators.

We investigate the local structural distortion induced by

This work highlights the capabilities and limits of X-ray computed tomography in crystallization monitoring through a use case involving paracetamol as the solute, recrystallized from ethanol, methanol, or a mixture of both. The cooling crystallization operation was set up in two different containers, prepared with cotton yarns stretched vertically, acting as linear nucleation sites that immobilize the grown crystals in the recording area. The largest container (10 mL test tubes) allowed the acquisition of a larger number of crystals (up to 300 particles) for a more appropriate bulk analysis. The smallest container (5 mL pipette tips) allowed for a finer resolution of the recorded solid phase at the expense of a reduced recording volume. Crystallization was monitored in terms of the number of individual crystals, their size, and the overall volume, thus leading to the nucleation and growth rates, and solid-phase production rate. The main benefit of X-ray computed tomography is in the 3D analysis of the reconstructed solid phase. The crystal habit of paracetamol form I was predicted using force-field modeling. The predicted habit was in great accordance with the reconstructed solids, confirming the polymorphic form. Furthermore, face-specific growth rates of reconstructed crystals were measured, paving the way for a novel approach to the investigation of crystal-solvent interactions.

AlGaN alloys with very high AlN mole fraction (∼90 %) were grown by plasma-assisted molecular beam epitaxy (PA-MBE) and their alloy properties were investigated by high-resolution X-ray diffraction (HR-XRD) measurements. Growth was carried out employing a series of group III/V ratios and for samples grown under a high group-III regime, phase-segregation in the alloy was evident from a characteristic splitting of the AlGaN (0002) peak in the HR-XRD pattern. With decreasing excess group-III conditions the separation of peak positions continuously reduced, till a single peak was observed. However, for samples where such splitting was absent, spontaneous superlattice peaks were seen at lower incident angles of the XRD patterns indicating the presence of long-range atomic ordering (LRAO). Thus, for AlGaN alloys with extremely high Al content, effects of phase-segregation, or of LRAO were observed, depending on the kinetics of growth. These results on phase-segregation effects are expected to promote the development of high-efficiency deep ultraviolet emitters for skin-safe germicidal action by mitigating the detrimental effect of dislocations and related non-radiative recombination centers through carrier localization processes at potential minima.

We propose a mathematical model of the thin molten silicon film to describe the quasi-steady shape of the inhomogeneous structures on the open melting front of polycrystalline feed rod during the floating zone process for single crystal silicon growth. As a result, precise shapes of the phase boundaries in a three-phase environment on a local scale were determined with the use of moving meshes. The presence of the local structures influences the heat transfer on the open melting front. Consequently, the global phase boundary model can be adjusted, resulting in improved agreement with the experimentally measured interface shape.

The rare-earth palladium silicides host an array of complex magnetic phases. In this paper, we report the growth of large single crystals of the $R_2$PdSi₃ family, (where $R=$ Ce, Nd, Gd, Tb, Ho and Er) by the floating zone technique using a high-power xenon arc-lamp furnace. The crystal boules obtained have been examined for their quality using x-ray diffraction techniques, elemental analysis, and their magnetic properties have been investigated through temperature dependent magnetisation measurements.

Crystal nucleation is crucial in various fields of science and technology, ranging from materials synthesis to pharmaceutical production. Our research aims to determine the nucleation rates from parallel induction time measurement experiments followed by low-cost external bulk video imaging. Stirred conditions are applied, making our results industry-relevant where the crystallizers are also mixed. The L-Glutamic Acid-water system (L-GA/water) is used as a surrogate. The study is conducted through a series of parallel, small-scale stirred experiments that explore the effects of supersaturation, temperature, and polymer additives on nucleation rates. The methodology involves careful data collection through controlled experimental setup and analysis of induction time distributions that the stochastic nature of nucleation explains the induction time distribution. The discussion section interprets the findings within the context of the research question, highlighting the implications of varying temperature and supersaturation levels as two experimental parameters and polymers on crystal nucleation rates. The specific parameters of supersaturation and temperature dependencies are in the range of those reported in the literature, which validated the developed rapid nucleation rate measurement platform. Stepping outside of these established measurements, analyzing the influence of polymers with high potential in controlling particle size, shape, and polymorphism was touched as well. As an unexpected result, the nucleation rates appeared to depend not only on the chemical structure and amount of the polymer but also on the polymer solution preparation method. The remarkable influence of polymers on nucleation rates was shown that cannot be explained with the solubility altering effect of the polymers alone.

In the industrial continuous casting process, some central defects such as shrinkage cavity, porosity, segregation and crack are generated especially at the final solidification zone of steel strands because of the poor fluidity and feeding ability of molten steel in the center of strand, especially for the special steel strand. In this paper, a new type of vertical linear electromagnetic stirring (V-LEMS) was proposed to apply in the casting of Incoloy 825 alloy ingot and investigate the growth and transition of dendrites, distribution of Ti in the special steel, and compare its effect with the generally conventional industrial rotary electromagnetic stirring (R-EMS). The results shown that the growth direction of primary dendrite under R-EMS is perpendicular to the mold wall, but the primary dendrite growth under V-LEMS have present an upstream dendrite growth state. It proves that the V-LEMS can generate a longitudinal circulation convection in the height direction of ingot, which can strengthen the temperature and composition mixing of the upper and lower melts of the ingot and promote the homogenization of the overall melt temperature and composition. The radial macrosegregation of Ti under V-LEMS is slightly higher than that of R-EMS, but R-EMS tends to increase the longitudinal macrosegregation of Ti element. The longitudinal macrosegregation degree of Ti element under V-LEMS is less than that without EMS and with R-EMS. V-LEMS makes the longitudinal distribution of Ti element in Incoloy 825 alloy ingot more uniform. The research results give some beneficial suggestions for improving the central quality of special steel continuous casting billet.

Cardiovascular disease represents the leading cause of death worldwide, according to the World Health Organization (WHO) report. One of the treatment strategies is the use of the drug ezetimibe (EZT). This drug is a cholesterol absorption inhibitor with low aqueous solubility, which affects its therapeutic efficacy. The purpose of this paper was to obtain eutectic materials of EZT with methylparaben (MPB), salicylic acid (SCA) and nicotinamide (NTM) coformers, and to study their phase diagrams, dissolution properties and hygroscopicity to assess possible enhancements. Phase and Tamman diagrams were constructed using differential scanning calorimetry (DSC) results. The eutectic materials were characterized by powder X-ray diffraction (PXRD) and polarized light optical microscopy (OM). The hygroscopicity of the materials was assessed at different relative humidities (RH) through dynamic vapor sorption (DVS). The dissolution study was conducted with the materials in powder form, with paddle dissolution, rotating at 50 rpm, in 900 mL of aqueous buffer solution at pH 6.8 and 37 °C. The phase diagrams demonstrated that EZT formed eutectic systems with eutectic molar fractions of 0.59, 0.67 and 0.69 for EZT-SCA, EZT-NTM and EZT-MPB, respectively. The three eutectic materials are characterized as microcrystalline conglomerates of their components. In terms of the hygroscopic behavior of EZT at different RHs, eutectic materials demonstrated lower susceptibility to monohydrate formation compared to the anhydrous form. In dissolution studies, EZT-SCA and EZT-MPB solubilized EZT in amounts 22 % higher than the pure drug in 15 min. On the other hand, EZT-NTM eutectic suppressed the dissolution of EZT down to 56 % at the same time. The results indicated the possibility of obtaining materials with enhanced properties using eutectic mixtures, with improved dissolution rates and hygroscopic stability.

The results of the study of the influence of a static magnetic field of 55 ± 3 mT on the face growth kinetics of sodium chlorate crystals in the supersaturation range of (0.89–1.78) % are presented. The supersaturation dependence of growth rate was analyzed using different theoretical models and the kinetic parameters of crystal growth in zero and in the applied magnetic field were estimated. It is shown that in both types of experiments the observed crystals grew by a complex dislocation source. Analysis of the growth rate distribution by using the Weibull distribution function was performed to obtain the maximum growth rate R_max depending on their corresponding initial length l_max. The linear relationship between these quantities is derived from the model of growth by a group of cooperating screw dislocations. It was observed that both the initial size threshold l*_max and the slope dR_max/dl_max exhibit higher values in the presence of a magnetic field.