Crystal Research and Technology最新文献

The Cu₂ZnSnS₄(CZTS) monocrystal as an important component of the optical absorption layer in monograin layer solar cells, has excellent crystallization characteristics and adjustable photogenerated carrier concentration. The shape of the CZTS monocrystal directly affects the utilization of incident light and the contact area during the preparation of the back electrode when they are densely packed to form a single-layer absorption layer. Herein, a kesterite-phase pyramid-shaped CZTS monocrystal prepared by the molten salt method is reported, which can improve the efficiency of incident light utilization and increase the contact area during back electrode preparation. The X-Ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy are used to characterize the crystallinity and crystal shape of pyramid-shaped CZTS monocrystal. Besides, Finite-Difference simulation calculation is employed to reveal the optical response and corresponding monograin layer solar cells performance of densely packed CZTS. The results show that the pyramid-shaped structure exhibited excellent incident light trapping ability, and the simulated device achieves a cell efficiency with above 13.6% after parameter optimization. The work provides a method for preparing pyramid-shaped CZTS monocrystal, and a new strategy to further improve the efficiency of CZTS-based monograin layer solar cells.

PbMo_0.3W_0.7O₄ semiconductor crystal, which contains the balanced ratios of Mo and W, is grown for the first time by Czochralski method. The structural and optical properties of the crystal are investigated in detail in the present study. Structural analysis shows that crystal has tetragonal structure like PbMoO₄ and PbWO₄ compounds. The optical characteristics are studied by transmission, Raman, FTIR and photoluminescence methods. The bandgap energy is found to be 3.18 eV, and the positions of the conduction and valence bands are determined. The vibrational characteristics are studied by means of Raman and FTIR spectroscopy techniques. Photoluminescence spectrum presents three peaks around 486, 529, and 544 nm which fall into the green emission spectral range. Taking into account the properties of the compound, it is stated that PbMo_0.3W_0.7O₄ (or Pb(MoO₄)_0.3(WO₄)_0.7) has the potential to be used in water splitting applications and optoelectronic devices that emit green light.

In this paper, the effect of trace components in dolomite on the morphology of vaterite calcium carbonate is studied in the CaCl₂-NH₃-CO₂ system, with a focus on the effect of cations (Mg²⁺, Fe³⁺, Si⁴⁺, and Al³⁺) in the solution. Ca²⁺, NH₄⁺, Mg²⁺, Fe³⁺, Si⁴⁺, and Al³⁺ in the digestion solution are proportionally prepared into a solution by analyzing the calcium rich digestion solution which is obtained by digesting dolomite with ammonium chloride solution. Under the optimal conditions, NH₃ is introduced at a rate of 0.5 L min⁻¹ for 1 h, CO₂ is introduced at a rate of 0.5 L min⁻¹ for 1 h and rotation speed of 500 r min⁻¹ to prepare the vaterite calcium carbonate. The results show that the addition of Mg²⁺, Fe³⁺, Si⁴⁺, and Al³⁺ can promote the growth of vaterite calcium carbonate. Among them, adding Mg²⁺ and Si⁴⁺ can promote the dispersion of vaterite, Fe³⁺ and Al³⁺ can cause agglomeration of vaterite. Material Studio software is used to predict the crystal morphology of vaterite calcium carbonate under ideal conditions, and the calculation results are basically consistent with the experimental results.

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.