Journal of Crystal Growth最新文献

Thin film crystal materials have excellent properties such as a fine-scale structure, high strain strength, and flame retardancy. In this work, the preparation of magnesium hydroxide thin films was achieved by analyzing the main exposed groups on the surface of magnesium hydroxide and utilizing self-assembly film technology in a hydrothermal system with triethanolamine as a crystal additive. By combining experimental and simulation calculations, the study explored the alterations in morphology and growth mode of magnesium hydroxide thin films, the adsorption of triethanolamine on different crystal surfaces of magnesium hydroxide, and the control of magnesium hydroxide crystal growth by dynamically adjusting growth unit diffusion in the system under the influence of triethanolamine concentration. The results showed that the addition of triethanolamine increased the concentration of OH^– ions in the solution, facilitating the adsorption of Mg(OH)₆⁴⁻ growth units on the (1 0 1) surface with more Mg-O bonds. This allows the magnesium hydroxide (1 0 1) crystal surface to serve as tangential growth drivers for the system, the normal growth of the crystal surface transitions to tangential extension, promoting the gradual expansion of the hexagonal wafer into crystal films. The regrowth mechanism of magnesium hydroxide thin films promotes the regrowth of crystals under hydrothermal conditions, and realizes the high value-added utilization of magnesite resources.

The flow pattern and carbon transport in the solution for the solution growth of silicon carbide (SiC) in an induction-heating system can be effectively controlled by adjusting the coil frequency to obtain a relatively uniform distribution of growth rate. In this paper, a global heat and mass transfer model was first verified by the SiC crystal growth experiment results at the coil frequency of 8 kHz. Then, the influence of coil frequency on the fluid flow, carbon concentration, and growth rate for the growth of SiC crystals was numerically investigated. The results indicated that electromagnetic convection (at low frequencies) greatly enhances the upward convection beneath the crystal and weakens the adverse effects of Marangoni convection, resulting in a uniform distribution of radial temperature along the growth interface. Consequently, the carbon transport from the crucible wall to the crystal center is strengthened, leading to a uniform region of high carbon supersaturation with a lower coil frequency. The optimal radial uniformity of the growth rate along the growth interface is achieved at the coil frequency of 3 kHz.

This study aims at the synthesis of a ternary phase crystal CaO.2MgO.8Al₂O₃ (CM₂A₈) in the Al-rich part of the ternary system CaO-Al₂O₃-MgO through two techniques: (1) sol–gel citrate and (2) solid-state reaction. Based on the measurement of particle size, density, phase analysis, nature of bounds, and microscopic observation, the effect of the processing technique on the crystal purity, crystallite size, and synthesis temperature of the as-prepared CM₂A₈ powder was investigated. Phases analysis (XRD patterns) showed in the sol–gel citrate combustion method almost a single-phase material (calcium aluminate magnesium phases) at relatively lower temperatures while in the solid-state method as-prepared CM₂A₈ powder with a small amount of spinel (MgAl₂O₄ = MA) and calcium hexaaluminate (CaAl₁₂O₁₉ = CA₆) secondary phases. The generated heat through the combustion of the reaction of ammonium nitrate and citrate-based complexes decreases the synthesis temperature of nanocrystalline CM₂A₈, and the CM₂A₈ phase is formed at a temperature of 1400 °C. While growth mechanism in the solid-state reaction method adheres to the two-dimensional nucleation theory and a thick hexagonal flake known as CM₂A₈ is produced at a temperature of 1700 °C. In comparison with the crystals synthesized by the solid-state reaction method, the powder density of the nanocrystals synthesized by a sol–gel combustion method exhibits higher values (3.54 g.cm⁻³ and 3.65 g.cm⁻³, respectively). Peak intensities in the 400–1000 cm⁻¹ range, according to FTIR measurements, correspond to metal–oxygen–metal (M–O–M) bonds (vibrations of Al–O stretching in Mg–O–Al and Ca–O–Al), and they grow as the temperature rises from 200 °C to 1400 °C, indicating that CM2A8 was the crystal that was formed. The morphological analysis (FESEM) revealed that most of the agglomerate particles synthesized by the sol–gel citrate combustion remained within the range of 50–83 nm, while the particles synthesized by the had particles as 1 μm. The specific surface area synthesized CM₂A₈ via the sol–gel method is in the range of 10–24 m²/g. The main advantages of the sol–gel citrate process are the high purity of the product, the narrow particle size distribution, and the achievement of uniform nanostructure at low temperatures.

This study focuses on the growth and characterization of crystalline LiNbO₃ (LN) piezoelectric fibers pulled by the Laser Heated Pedestal Growth (LHPG) technique. The electrical properties of the fibers were investigated using an impedance analyzer, which yielded values for resonance frequency, anti-resonance frequency, and phase angle. Subsequently, elastic constants and coupling factor were determined through calculations based on thickness resonance modes. The accuracy of the resonance method was validated through numerical simulations utilizing COMSOL software, demonstrating a close agreement between experimental and simulated results. Additionally, a temperature sensing was conducted, subjecting the fibers to a wide temperature range from 30 °C to 236 °C to assess their sensitivity to temperature variations. The coupling factors of K = 0.37 for LN-1 and K = 0.35 for LN-2 demonstrated efficient performance of the crystalline fibers. Furthermore, the numerical simulations exhibited strong correlation between simulated and experimental data. The sensitivity analysis revealed the potential of LN fibers for temperature sensor applications, exhibiting a sensitivity of −87 Hz.°C⁻¹. These findings underscore the promise of LN piezoelectric fibers in advanced sensing technologies.

In this work, we prepared both chemical and biogenic synthesis of MnSrO₂ (0, 5, 20 ml DLE) nanoparticles using datura metel leaf extraction by co-precipitation method and also prepared Sulfadiazine dye for catalytic activity. The applications and properties of green MnSrO₂ nanoparticles have compared and they were characterized via XRD, SEM, FT-IR, EDX, UV–visible, and PL techniques. These nanoparticles showed an 18–8 nm diameter range, which was arranged in a spherical form combined randomly. The evidence from FTIR spectra showed peaks around 492, 487, 483, 655, 606, and 603 cm⁻¹ for the creation of SrMnO₂ NPs. Antibacterial activity of MnSrO₂ (0, 5, 20 ml DLE) was measured by the well-diffusion method against pathogens, Staphylococcus aureus and Klebsiella pneumonia. The photocatalytic activity of the synthesized metal oxide nanoparticles was investigated by UV–visible spectroscopy for Sulfadiazine dye degradation with bare MnSrO₂ NPs, g-MnSrO₂ NPs [5 ml DLE], and g-MnSrO₂ NPs [20 ml DLE] in presence of visible light irradiation.

This study investigates the controversies about the gas-phase reaction path in the InN MOVPE process. Numerical modeling of the reaction-transport processes in three typical reactors was conducted for main reaction paths. By comparisons of the molar concentrations of the major In-containing species, it was determined that the different approaches of the gas mixing and heating led to three distinct reaction paths. When the non-premixed gas precursors are heated very fast upon entering the reactor, the adduct/amide formation path predominates and the pyrolysis path is negligible (Path 1). When the precursors are mixed at room temperature and heated gradually, the adduct TMIn:NH₃ dissociates back into TMIn, with the pyrolysis path dominating. However, the formation of amides DMInNH₂ intensifies the generation of nanoparticles (Path 2). When mixing occurs at warm temperature and heated fast, both the pyrolysis and adduct paths co-exist, but their effects are different (path 3). In the CCS reactor the dominant reaction path will be Path 1, while in the vertical reactor with a greater height, Path 2 is predominant. In the pre-mixed horizontal reactor, Path 3 is dominant, the pyrolysis path forms a competition with the adduct path near the substrate, and the adduct path dominating at the top of the reactor.

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.