Crystal Research and Technology最新文献

The main theme of this work is to synthesize and investigate different properties of Pr³⁺-Cu²⁺ substituted X-type hexaferrite Sr_2-xPr_xCo₂Fe_28-yCu_yO₄₆ with concentration (x = 0, 0.02, 0.06, 0.1 and y = 0, 0.1, 0.3, 0.5) by adopting the sol–gel method. The XRD patterns show the single phase for all the samples. The Pr³⁺-Cu²⁺ substitution in pure X-type hexaferrites changes the structural parameters. The increment in dielectric properties with Pr³⁺-Cu²⁺ substitution is observed and the patterns show anomalous dielectric behavior. The FTIR analysis also confirms the single phase for the prepared materials. The magnetic properties of the material are enhanced with additives. The difference in saturation magnetization, coercivity, and remanence is observed on the basis of allocated cations onto the different lattice sites. The linear increase in saturation magnetization, remanence, and coercivity make them useful as permanent magnets. The thermal analysis is carried out to know the sintering temperature at which the single X-type phase can be attained. The material exhibits the minimum value of reflection loss (microwave absorption) at higher frequencies that make this material useful to act as microwave absorbing material (MAM) for super high frequency (SHF) devices.

Heavy metal in excess quantity is one of the major inorganic pollutants in water. It causes several hazards to human life and ecosystem. It exists in traces in most of the commonly available drinking water sources from lakes, ponds, wells, etc., However, their presence in treated water is relatively significant. As the treated water is primarily used for agricultural purposes, it is necessary to monitor and measure their concentration. This requires sensing of metals in aqueous medium with good sensitivity and stability. Recently, nanosensors coupled with electrochemical transducer is preferred for analyzing heavy metal in aqueous solutions. In this work, Silver oxide-bismuth oxy bromide coated with nafion is proposed as an electrochemical sensor for detection of heavy metal ions in aqueous solution. Cyclic voltammetry (CV) behavior of the proposed electrode is observed in different electrolytes. Further, Differential Pulse Voltammetry (DPV) study shows that current increases with trace nickel and copper metal ions of different concentration. Further, machine learning (ML) algorithms such as Naïve Bayes, ANN, SVM and decision trees are employed for nickel ions to train the cyclic voltammetry data and evaluate its performance. Naïve Bayes algorithm provides the best accuracy of 93.2% among all the models.

This study concerns the synthesis and structure related electrical property analysis of CaO doped ZrO₂@mullite composites. Two synthesis techniques (solid state reaction route and thermal plasma sintering) are used which results the formation of a composite consisting of mixed phase of orthorhombic mullite, tetragonal and monoclinic zirconia. The lattice parameters, residual strains, average crystallite size and cell volume of these CaO-doped ZrO₂@mullite composites are obtained from XRD analysis. Stabilization of t-ZrO₂ phase at room temperature is confirmed. Porous microstructure observed in SEM images results in low dielectric constant value of these composites. At room temperature and selected frequency of 1MHz, the dielectric constant and loss factor of 4.7 and 3.826 × 10⁻² is observed for conventional CaO stabilized ZrO₂@mullite composite and that of 3.8 and 2.19 × 10⁻² is reported for plasma sintered CaO stabilized ZrO₂@mullite composite. The impedance spectroscopic analysis demonstrates the negative temperature coefficient of resistance (NTCR) behavior and non-Debye type relaxation behavior of both the CaO stabilized ZrO₂@mullite composites. A negligible effect of electrode polarization is realized in these composites. The electronic band gap of conventional and plasma sintered CaO stabilized ZrO₂@mullite composites is found to be around 3eV.

Seeding metastable zone of itaconic acid in water is determined using a laser dynamic detecting technique, based on which feedback supersaturation control is performed for the crystallization process. The crystallization is strictly confined within the metastable zone throughout the whole process to effectively inhibit the secondary nucleation and the strategy of seed loading is employed to avoid the burst of primary nucleation, resulting in the uniform particle size distribution. With the aid of solution information, continuous feedback control is conducted to keep the supersaturation at a high level accelerating the crystal growth, which significantly shortens the time consumption, and also the effect of seed amount is discussed in this work.

Silicon epitaxy is a crucial process used in semiconductor manufacturing to deposit high-quality films of silicon. This technique is widely used in the production of integrated circuits, as it enables the fabrication of intricate electronic structures with enhanced performance characteristics. This study conducts numerical simulations on a chemical vapor deposition (CVD) reactor to explore the impact of process parameters on the growth rate and non-uniformity of silicon. The investigation encompasses both the gas and surface reactions of the trichlorosilane-hydrogen (TCS-H₂) system. The distributions of gas flow velocity, temperature, and main components are systematically studied by varying the process parameters, including susceptor temperature, inlet gas velocity, susceptor rotating speed, inlet gas temperature, upper wall temperature, and TCS mole fraction. Furthermore, the orthogonal test method is introduced to assess the effect of all parameters on the growth non-uniformity. The results reveal that the inlet gas velocity and susceptor temperature have a significant influence on the growth rate and non-uniformity. The silicon growth rate is primarily influenced by the TCS mole fraction, whereas the rotation speed of the substrate primarily influences the growth non-uniformity of growth. Finally, the optimal scheme is proposed as valuable guidance for enhancing silicon chemical vapor deposition processes in industrial applications.

Ternary chalcogenide PbGa₂Se₄ with high resistivity, photosensitivity, and excellent nonlinear properties, exhibits a potential application in optoelectronic and nonlinear optical devices. However, the preparation of large-sized pure PbGa₂Se₄ crystals is challenging due to the presence of peritectic reaction $��L�+�\alpha ��\left(��G�a_2�S�e_3��\right)��\to �P�b�G�a_2�S�e_4�$ and a narrow homogeneity region. Here, a “quenching-annealing” method (quenching at 850 °C in ice water, and then annealing at 650 °C for 250 h by reheating) is developed to eliminate the PbSe second phase during the synthesis. Subsequently, the PbGa₂Se₄ single crystals are successfully grown using chemical vapor transport (CVT) with the I₂ as the transport agent. The resulting crystal exhibits the crystal structure belonging to Fddd space group with the lattice parameters of a = 12.7192 Å, b = 21.2831 Å, and c = 21.5226 Å. Additionally, it possesses a wide bandgap (≈2.26 eV), high resistivity (6.59 × 10¹² Ω·cm), and defect density calculated via space charge limited current measurement (SCLC) as 2.46 × 10¹¹ cm⁻³. Photodetectors based on these as-grown crystals demonstrate exceptional photosensitivity along with a high detectivity (3.2 × 10⁸ Jones).

Cover image provided courtesy of Jianguang Zhou, Research Center for Analytical Instrumentation, Institute of Cyber-Systems and Control, State Key Laboratory of Industrial Control Technology, Zhejiang University, China.

The molecular structure and spectroscopic data of (2E)-1-(Anthracen-9-yl)-3-(4-nitrophenyl)prop-2-en-1-one are obtained from DFT (B3LYP) with 6-31G(d,p) and 6-31G+(d,p) basis set calculations. The geometry of the molecule is fully optimized, vibrational spectra are calculated and fundamental vibrations are assigned on the basis of potential energy distribution (PED) of the vibrational modes. Molecular parameters such as bond length and bond angle are calculated with the same level of theory. The intramolecular charge transfer is calculated by means of natural bond orbital analysis (NBO). Besides, the molecular electrostatic potential (MEP), HOMO - LUMO, Fukui functions, RDG and ELF are performed. The biological effect is made on the basis of prediction of molecular docking results.

The solution combustion synthesis method is employed to prepare Magnesium,  Zinc, Aluminate doped with dysprosium (Dy³⁺) using the general formula Mg_(1-x-y) Zn_(y)Al₂O₄:xDy (x = 0.05 and y = 0.3 mol%). From X-ray diffraction studies, the crystal structure belongs to a cubic close-packed spinel structure with space group Fd3ˉm and an average crystallite size is 26.18 nm. In the Fourier transform infrared spectra, the peaks at 683.69 cm⁻¹, 503.12 cm⁻¹ correspond to the AlO₆ groups. The peak temperature (Tm) from the Thermoluminescent glow curve is recorded at 235°C, 237°C, and 235°C, at irradiation doses of 600 Gy, 800 Gy, and 1000 Gy, respectively. The kinetic parameters are evaluated from the thermoluminescent glow curve by calculating the activation energy (E), order of kinetics (b), and frequency factor (s⁻¹). Nanophosphor Mg_0.65Zn_0.3Al₂O₄:0.05Dy shows sub linear dose relationship at doses 600–675 Gy and 925–1000 Gy. Further, at doses between 675 and 925 Gy, it shows a super linear relationship. The optimum activation energy (E) of 0.77–0.82 eV and negligible fading make it suitable for high radiation thermoluminescent dosimetry.