Crystal Research and Technology最新文献

The formamidinium lead iodide (FAPbI₃) perovskite has emerged as a promising material for high-efficiency photovoltaic applications. Although a power conversion efficiency of more than 26% has been achieved, stability issues have hindered its commercial application. In this study, the stability of FAPbI₃ under adverse conditions such as humidity, oxygen, ultraviolet light, and temperature fluctuations is systematically reviewed. The known effective strategies for improving stability are discussed. Current studies have shown that technologies such as doping, halide alloying, additive manufacturing engineering, and interface modification have been identified as effective in mitigating phase transitions of FAPbI₃ and enhancing environmental durability. Encapsulation technology further improves moisture and heat resistance. Compared with other stabilization strategies, doping and alloying can address the adverse effects of narrowing of the absorption edge. Interface engineering has an essential understanding of the stability mechanism, which will greatly improve the stability problem in the practical application of FAPbI₃. This paper also looks forward to the future research directions and development trends.

Nowadays, double perovskite materials are playing an exceptional role in the field of optoelectronics, spintronics, and photovoltaics as they exhibit outstanding characteristics. In the present work, a comprehensive examination of the mechanical, electrical, optical, thermal, and structural characteristics of the K₂InAsCl₆ double perovskite complex is conducted by using the density functional theory via Wien2k software. The K₂InAsCl₆ exhibits structural, thermodynamic, and mechanical stability which is evaluated through several parameters. The K₂InAsCl₆ possess a direct band gap of 0.5 eV which is also endorsed by the total density of states (DOS). The K₂InAsCl₆ exhibits ductile character and longitudinal waves are found to be predominate over transverse waves. Furthermore, the optical analysis indicates that the material's intricate electrical configuration is suitable for significant optical activity across the visible spectrum. The versatility of K₂InAsCl₆ is well-proven by its robust thermal and mechanical properties. It exhibits excellent ZT value (0.92) at room temperature which confirms its potential for green energy applications.

How to increase the stereocomplex crystal (SCs) content of polylactic acid attracts a lot of attention from scientists. In the current work, Monte Carlo simulations are used to construct grafted diblock copolymer systems with different grafting modes and the stereocomplex crystallization of these systems is studied. The results show that the SC contents are highest in the random-grafted, the row-staggered-grafted and the point-staggered-grafted copolymer systems, while the SC content is lowest in the uniform-grafted copolymer systems. This can be attributed to that the random-grafted, the row-staggered-grafted and the point-staggered-grafted copolymer systems have the highest local segment miscibility, while the uniform-grafted copolymer system has the lowest local segment miscibility. In addition, it is also found that the point-staggered-grafted copolymer systems with lower chain lengths exhibit higher SC contents due to the stronger segment mobility.

Para aminobenzoic acid (p-ABA), a well-known pharmaceutical material with a challenging polymorphic nature, is chosen for study in this paper. The material has four reported polymorphs, containing two solution forms (α and β), a vapor form, and a high-pressure form. The solution-grown forms α and β are experimentally grown using mixed solvents of water and isopropyl alcohol with nine different mixing compositions at temperatures of 298, 303, and 308 K. The solubility of the commercially available p-ABA is calculated gravimetrically, and the polymorphic crystals are grown using the slow solvent evaporation method for all the mixing ratios at different temperatures. A ternary diagram constructed on the solubility of p-ABA in mixed solvents gives an insight into the nucleation nature of two polymorphs. To understand the nature of nucleation and growth of two forms of p-ABA, an in situ microscopic study is carried out, and the grown crystals are characterized using powder X-ray diffraction analysis and differential scanning calorimetry. This also confirmed that the grown crystals are two solutions grown polymorphs of para aminobenzoic acid, both belonging to monoclinic systems with P2₁/n space group.

The growth, ion concentrations, powder X-ray diffraction, thermal properties, and optical spectroscopy of Nd³⁺-doped Ca₃(BO₃)₂ single crystals are investigated. The Nd³⁺-doped Ca₃(BO₃)₂ single crystals with 1.97 at.% Nd³⁺ are successfully grown using the Czochralski (Cz) technique. To address the chemical valence imbalance between Nd³⁺ and Ca²⁺ in the Ca₃(BO₃)₂ crystals, the Na⁺ ions are introduced. The concentrations of Nd³⁺ and Na⁺ ions in the as-grown crystals are measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES), yielding concentrations of 1.97 at% (N₀ = 1.55 × 10²⁰ cm⁻³), 1.94 at% (N₀ = 1.52 × 10²⁰ cm⁻³), respectively. The thermal behavior of the Nd³⁺-doped Ca₃(BO₃)₂ crystals, including thermal expansion coefficients, specific heat, and thermogravimetric and differential thermal analysis (TG-DTA), is systematically investigated. At room temperature, the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay lifetimes are measured. Spectral parameters, including polarized absorption and stimulated emission cross-sections, intensity parameters, transition probabilities, radiative lifetime, and branching ratios are determined using the Judd-Ofelt (J-O) theory. The results indicate that Nd³⁺-doped Ca₃(BO₃)₂ crystals are promising materials for near-infrared lasers, offering advantages such as rapid growth, large size, high specific heat, strong emission, and environmental stability.

Rare earth alloying is one of the effective ways to improve the performance of magnesium alloys, but strong galvanic corrosion occurs when rare earth magnesium alloys meet corrosive substances. To improve the corrosion resistance of rare earth magnesium alloys, this article takes Mg-13Gd-4Y-2Zn-0.5Zr rare earth magnesium alloy as the research object. First, a one-step micro arc oxidation process is used to obtain the film layer. The experiment shows that when the chemical composition and concentration of the electrolyte are constant, changing the voltage parameter of the one-step micro arc oxidation alone cannot prepare a thick, dense, and corrosion-resistant micro arc oxidation film layer, which cannot meet the practical application needs of rare earth magnesium alloys. Then, the one-step micro arc oxidation film layer is used as the substrate sample. By changing the voltage parameters, the sample is subjected to a second micro arc oxidation treatment to prepare a two-step micro arc oxidation film layer. In the study, it is found that the two-step microarc oxidation process increased the thickness of the film layer, which has good densification and corrosion resistance at a voltage of 452.5 V, improving the corrosion resistance of the film layer.

A crack-free and high structural quality Sr₂Nb₂O₇ single crystals are grown by the optical float zone method using optimized growth parameters. The Laue pattern confirms the single crystalline nature of the grown crystal. Temperature-dependent Raman and Brillouin light scattering studies reveal a significant shift in phonon modes across normal to incommensurate phase transition (T_n-in) which occurs ≈488 K. In the temperature range from 900 down to 500 K, two optical phonon modes ≈63 (B1 mode) and 54 cm⁻¹ (A1 mode) are observed. The frequency of A1 mode strongly decreases with an increase in temperature above the T_n-in while the frequency of this mode almost remains constant below the T_n-in. In contrast, the frequency of B1 phonon mode is found to increase with temperature in the range of 500–900 K but it does not display a significant shift below the phase transition temperature. In addition, in the in-commensurate phase (T< 488 K), a new optical phonon mode (M1) at ≈35 cm⁻¹ also begins to appear and exhibits strong stiffening behavior with an increase in temperature in the range of 300–488 K. Moreover, the anomalous behavior of the acoustic phonon across T_n-in are further probed using Brilliouin scattering. Longitudinal acoustic phonon mode at 41 GHz exhibits a strong change in slope near T_n-in. In addition, the transverse acoustic modes at 28.6 and 22.4 GHz also exhibit strong anomalies with minimum frequency near T_n-in. The inelastic light scattering studies provide valuable information on the phase transition.