Crystal Research and Technology最新文献

The formation of solid solutions in the CaMoO₄-CaWO₄ binary system is investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy methods. The intermixtures of CaMoO₄ and CaWO₄ components are sintered in 600—1200 °C temperature range (in 100 °C increments). The solidus of the CaMo_xW_(1-x)O₄ system is studied by the differential scanning calorimetry method in the x  =  0.3 … 1.0 range. CaMoO₄-CaWO₄ phase diagram is constructed up to 1550 °C. The minimal sintering temperature in order to get CaMo_xW_(1-x)O₄ solid solution is shown to be 800 °C. Cathodoluminescence study of CaMo_xW_(1-x)O₄ compounds showed higher intensity of molybdate luminescence type.

In this paper, a crystal plasticity finite element method (CPFEM), considering the grain morphology and orientation, as well as the dislocation density, is used to research the tensile deformation behavior of GH4169 based on Electron Backscatter Diffraction (EBSD). The stress, plastic strain, and dislocation density distributions are obtained for different levels of deformation. Results show that the stress, plastic strain, and dislocation density exhibit obvious heterogeneous plastic deformation, and stress concentration and dislocation pileup mainly occurs near grain boundaries. The initial dislocation density mainly affects the stress–strain curve of the material, and it can obviously effect the yield strength but cannot influence the hardening ability of the material. The total dislocation density increases with plastic strain. However, the texture evolution has no evident change with increasing plastic strain, except for the increase of texture content in Cube (001)[100].

Laser-quality yttrium-aluminum garnet single crystals doped with neodymium (YAG:Nd) of a concentration up to 1 at. % is grown by the method of horizontal directional crystallization from a molybdenum crucible in the protective reducing atmosphere based on argon, СО, and hydrogen. It is found that the content of carbon impurity in the grown crystals does not exceed 5·10⁻³ wt %, the content of molybdenum being on the level of 1.5·10⁻³ wt %. The optical quality of the crystals depends on the composition of the growth atmosphere and annealing. It is shown that, besides the bands of neodymium ion absorption, the crystals are characterized by the intense absorption in the UV edge of the spectrum at 370 nm wavelength, and by the wide absorption band with a maximum at 580 nm caused by formation of F and F⁺-centers. The absorption at 370 and 580 nm can be eliminated by annealing. The structure perfection of the crystals is characterized by the rocking curve half-width (β) which value varies within the limits of 10–14 arc. sec for (001) plane. Laser testing demonstrates the parameters comparable with those of YAG:Nd crystals grown by the Czochralski method from iridium crucible.

Bis(8-hydroxyquinolates) Zinc (Znq₂) can be used as a light-emitting layer material in OLED devices to achieve its efficient electroluminescence effect. In this paper, Znq₂ powder has been successfully synthesized and modified by the physical vapor deposition (PVD) method. Precursors and nano-materials are characterized by XRD, SEM, PL, and so on. The performance of the modified material has been significantly improved. The emission intensity and absorption intensity in the deposited products increased with the increase in PVD temperature. At 453 K, luminous properties such as luminous intensity reach the optimal value including its fluorescence lifetime. Fluorescence lifetime values vary from 13 to 17 ns with the increase in temperature. The luminescence mechanism is also discussed. The energy gap and absorption spectrum of HOM-LUMO are calculated by the DFT/UB3LYP method. The experimental values agree well with the theoretical values. The nanomaterial crystals modified by PVD technology are more orderly, impurities are reduced, and the luminous stability of the material is improved, which may be one of the reasons for the relatively slow decline in product life. The research combined with theoretical simulation is expected to be helpful to the research and promotion of such materials.

The synthesis of copper nanocrystals on tartaric acid jute composite surface is reported. The formation of nanocrystals is detected by FT IR, Powder X-ray diffraction, SEM, and TEM analysis. The average size of the nanocrystals is found to be 500 nm. The reaction of the copper nanocrystals with CO₂ resulted in a decrease in the size of the nanoparticles. Cycloaddition reaction of epoxides to cyclic carbonate is efficiently carried out by the copper nanocrystals on tartaric acid jute composite surface (CUNPJT) without using any cocatalyst and solvent. To the best of author's knowledge, this is the first example of copper nanocrystals catalyzing the cycloaddition of CO₂ and epoxide.

[Hanen Alhussain, Hela Ferjani, Youssef Ben Smida; https://doi.org/10.1002/crat.202300340]

[An error in the spelling of an author's name in the article. The name in the published paper is [Hanen] and should be corrected to [Hanan].

We apologize for this error.

Morphology-controlled Cs₂SbBr₆ crystals are synthesized by Bi- and Ag-substitution of the precursor solution. X-ray diffraction (XRD) together with Raman spectroscopy confirms the lattice tilting and symmetry changes with the dominant appearance of higher index facets by Bi substitution. Ag substitution does not induce crystal symmetry changes in the Cs₂BBr₆ (B = Sb or Bi) phase, but results in highly defective structures hindering the formation of a smooth surface during the crystal growth. Successful substitution of Bi and limited substitution of Ag into Cs₂SbBr₆ is also confirmed by energy dispersive X-ray spectroscopy (EDX). This research provides design principles and practical examples of how to control the morphology of Cs₂SbBr₆ crystals with structural defects and multiphase formation.

Pristine tin selenide (SnSe) and copper (Cu) doped SnSe single crystals are grown by direct vapour transport technique. The energy dispersive X-ray, X-ray diffraction and Raman spectroscopic analysis of grown crystals show preferred stoichiometry having a single phase othorhombic SnSe. The electrical conductivity of SnSe and Cu doped SnSe are 24.24 and 106.06 S m⁻¹ at 310 K respectively which increase as temperature increases. Carrier concentration of grown single crystals are evaluated by the Hall effect. Lattice thermal conductivity of pristine SnSe is 0.61 W mK⁻¹, that decreased by copper doping to 0.44 W mK⁻¹ at 310 K and for both the crystals it shows decrement as temperature increases to 483 K. Seebeck coefficient of the grown SnSe and Cu doped SnSe are positive and obtained values are 536.44 and 492.90 µV K⁻¹ respectively at 310 K that confirm the p-type semiconducting nature. Power factor, Figure of merit and thermoelectric compatibility factor of grown pristine SnSe is 0.25 × 10⁸ µV mK⁻², 0.005 and 0.02 Volt⁻¹ respectively and shows improvement in Cu doped SnSe, i.e., 0.08 × 10⁸ µV mK⁻², 0.017 and 0.07 Volt⁻¹ respectively at 310 K. This shows Cu doping in SnSe makes it an effective thermoelectric device contender.