物理与天体物理最新文献

The synthesis and the structural and luminescence studies of samarium-doped calcium aluminate phosphors are reported. These phosphors are synthesized by the solid-state reaction method with a variable concentration of doping ions (0.5–3.0 mol%). The synthesized phosphors are characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The XRD studies show that the doped phosphors have a cubic structure. The SEM images reveal that the Sm³⁺- doped Ca₃Al₂O₆ phosphor represents a combination of some rod-like and flower-like structures. The FTIR studies confirm the formation of a Ca₃Al₂O₆:Sm³⁺ phosphor. The photoluminescence (PL) emission measurements upon excitation by 273 nm (ultraviolet light) show the characteristic emission peaks of Sm³⁺ at 579, 589, 600 and 619 nm. The characteristic orange-red emission is observed for samarium ion. The excitation spectra of the Ca₃Al₂O₆:Sm³⁺ phosphor mainly consist of a more intense charge transfer band (CTB) of Sm³⁺ located at 273 and 395 nm with some peaks centred at 319 and 362 nm. The CIE coordinates are calculated by the spectrophotometric method using the spectral energy distribution of the Ca₃Al₂O₆:Sm³⁺ sample. The prepared phosphors can act as a single host for orange-red light emission in display devices.

The paper presents the comprehensive analysis of the structure, properties, and corrosion of micro-arc coatings with ZrO₂ and TiO₂ particles after the low-energy high-current electron beam (LEHCEB) treatment. The coating morphology, microstructure, phase and elemental compositions are investigated by the scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray powder diffraction. After the LEHCEB treatment, the coating structure with ZrO₂ particles changes from friable and porous to denser with closed spheroidal pores. It is shown that the adhesive strength of the coating with ZrO₂ particles increases with the critical load growth from 10 to 18 N. Moreover, the treatment enhances its corrosion resistance, as evidenced by a reduction in the corrosion current from 7.48∙10^–7 to 1.05∙10^–8 A/cm² and an increase in polarization resistance from 0.9·10⁴ to 5.77∙10⁶ Ω·cm². In contrast, the coatings with TiO₂ particles exhibit a more porous structure due to the volatilization of low-melting components (sodium silicates), as evidenced by a reduction in the concentration of Na and Si elements in their composition. The adhesive strength and corrosion resistance of the coatings with TiO₂ particles deteriorate after the treatment.

Quasiperiodic magnonic crystals, in contrast to their periodic counterparts, lack strict periodicity which gives rise to complex and localised spin wave spectra characterized by numerous band gaps and fractal features. Despite their intrinsic structural complexity, quasiperiodic nature of these magnonic crystals enables better tunability of spin wave spectra over their periodic counterparts and therefore holds promise for the applications in reprogrammable magnonic devices. In this article, we provide an overview of magnetization reversal and precessional magnetization dynamics studied so far in various quasiperiodic magnonic crystals, illustrating how their quasiperiodic nature gives rise to tailored band structure, enabling unparalleled control over spin waves. The review is concluded by highlighting the possible potential applications of these quasiperiodic magnonic crystals, exploring potential avenues for future exploration followed by a brief summary.