Physics of the Solid State最新文献

This study explores the structural, morphological, optical and photoluminescent properties of pure CdO, CdO/La₂O₃, and CdO/La₂O₃/PVP nanocomposites synthesized via the microwave irradiation method. XRD analysis confirms the face—centered cubic phase of CdO and the successful incorporation of La₂O₃ and PVP, evidenced by changes in lattice parameters and reduced crystallite sizes. Fourier transformed infrared spectroscopy (FTIR) analysis detects functional groups associated with La₂O₃ and PVP, confirming their integration into the CdO matrix. TEM reveals smaller particle sizes, improved dispersion and enhanced crystallinity in the composites. UV-Vis spectroscopy shows a bandgap increase from 3.4 eV (CdO) to 4.2 eV (CdO/La₂O₃/PVP), attributed to the Burstein–Moss effect and structural changes. PL studies indicate enhanced multi-band emissions and defect related transitions, suggesting improved charge separation and reduced recombination. Under UV irradiation, CdO/La₂O₃/PVP exhibits the highest photocatalytic degradation efficiency for MB dye (65.77% in 120 min), outperforming CdO/La₂O₃ (48%) and pure CdO (22%) due to smaller particle size, more active sites, and better charge carrier separation. These results demonstrate the potential of CdO-based nanocomposites in photocatalysis, optoelectronics and energy harvesting applications.

This study investigates the electrical and magnetic characteristics of chromium phosphide (CrP) through the introduction of transition metal (TM) atomssuch as Mn and Fe, as dopants. The FP-LAPW method has been employed under the density functional theory (DFT) framework, utilizing the WIEN2k software. The GGA approximation was utilized as the exchange-correlation potential to determine the solution of the Kohn–Sham equation. To study the band structure, the full potential linearized augmented plane wave (FP-LAPW) method has been utilized. The stable atomic structure of chromium phosphide has been derived from the zinc blende (ZnB) configuration. Furthermore, Cr_1–xTM_xP demonstrates a zinc-blende phase when doped with x = 0.125 and 0.25 concentrations. The phenomenon of half-metallic behavior is exhibited in CrP when the atomic constants are greater than or equal to 4.48 Å, and the muffin-tin radii (RMT) of Cr and P are set at 2.28 and 2.01, respectively. Analysis of Cr_1–xTM_xP (TM = Mn and Fe) at different doping concentrations (x) reveals that the material retains its half-metallic characteristics at low doping levels, but this feature declines as the doping levels increase. The magnetic moments of Cr_0.75Fe_0.25P are greater than those of Cr_0.75Mn_0.25P because of the interaction between the hybridized 3d-orbitals of the host Cr and the dopant Mn/Fe. These findings indicate that Cr_1–xTM_xP (TM = Mn and Fe) at low concentrations have great potential as materials for spintronic applications.

Urea-L-malic acid crystals doped with zinc (II) (Zn:ULM) were grown through the process of gradual evaporation. From the X-ray diffraction (XRD) study it was found that the Zn:ULM structure relates to a monoclinic crystal symmetry. UV-visible analysis indicated that the Zn:ULM is incredibly transparent in the UV-visible range with a bandgap of 4.95 eV. According to Kurtz and Perry measurements, the Zn:ULM produced second harmonics 2.25 times that of the potassium dihydrogen phosphate (KDP) value. Thermogravimetric and differential scanning calorimetry (TG-DSC) methods were deployed to assess the thermal stability of Zn:ULM. The dielectric parameters of Zn:ULM were assessed within the 100 Hz to 5 MHz range. Jonscher’s theory was used to explain the mechanisms underlying electrical conductivity. We used impedance spectroscopy to gain more insight into the conductivity process. The findings show that the Zn:ULM crystals are appropriate for optoelectronic uses.

Since the discovery of the room-temperature superconductor Pb_10–xCu_x(PO₄)₆O (0.9 < x < 1.1) (LK-99) as reported by Lee et al. (http://arxiv.org/abs/2307.12008), the material have attracted wide attention from researchers, however subsequent studies by Chang Liu, Kaizhen Guo et al. have refuted LK-99 superconductivity claims (Phys. Rev. Mater. 7, 084804 (2023); Sci. China: Phys. Mech. Astron. 66, 107411 (2023)). The thermodynamic properties of material are one of the important factors for its practical applications, so it is necessary to conduct in-depth research on the parent compound Pb₁₀(PO₄)₆O. In this paper, we employed the first-principles method combined with the quasi-harmonic Debye model approximation calculations to study Pb₁₀(PO₄)₆O. Key thermodynamic quantities of Pb₁₀(PO₄)₆O are presented. For example, at 300 K, the bulk modulus value is 155.4 GPa, the coefficient of thermal expansion is 3.04 × 10^–5 K^–1, the entropy is 24.05 J/mol K, the vibration free energy is 1.12 KJ/mol and the specific heat capacity at constant volume is 22.25 J/mol K for the system at 10 GPa. Comparing with the results at 900 K, it is found that bulk modulus, bulk expansion coefficient and fixed volume heat capacity are more weakly affected by temperature, while the entropy and vibration free energy are strongly affected by temperature. These findings provide valuable theoretical insights and expand the research for related materials, such as Pb_10–xCu_x(PO₄)₆O.

In this paper, we have theoretically stadied a magnetic field sensor that operates by exciting Tamm plasmon resonance within the framework of one-dimensional photonic crystals. The sensor’s design incorporates a thin metallic layer strategically placed on the upper surface of the photonic crystal structure. To analyze the reflectivity characteristics of this sensor, we have employed several theoretical approaches, including the Drude model, the Faraday effect, and the widely recognized transfer matrix method. Our numerical investigations have highlighted thorough an optimization process directed at enhancing the sensor’s overall performance. In this regard, to get the best performance and sensor’s sensitivity, we explored the influence of various parameters, such as the specific type and thickness of the metallic layer, the different types and thicknesses of the layers constituting the photonic crystal, as well as the angle of incidence of incoming light, on the sensitivity of the sensor. Remarkably, the developed magnetic field sensor exhibited a sensitivity of 0.0016 nm/T, indicating its potential efficacy. This innovative design could be valuable in a wide range of applications related to the detection of magnetic fields, thereby contributing to advancements in this field.

This study explored the synthesis and characterization of aluminum-doped zinc oxide (AZO) nanostructures and their europium (Eu)-doping. AZO nanostructures were synthesized via a sol–gel method followed by supercritical ethanol drying, with Eu incorporated at 0.5 and 1% concentrations. Various analytical techniques were used to investigate their properties. X-ray diffraction (XRD) confirmed a hexagonal wurtzite structure in both AZO and Eu:AZO nanostructures. While Eu-doping slightly reduced crystal quality, crystallite size remained largely unchanged. Lattice parameters increased due to Zn²⁺ substitution by Eu³⁺. Diffuse reflectance spectroscopy (DRS) revealed an enhancement in reflectance upon Eu-doping, with the average visible reflectance increasing from 79.5 to 85%, while a slight reduction in the bandgap from 3.24 to 3.22 eV was observed. Fourier-transform infrared (FTIR) and attenuated total reflectance (ATR) spectroscopies displayed similar absorption bands across samples, with Eu co-doping reducing the intensity of the Zn–O vibrational band, indicating fewer Zn–O bonds. Scanning electron microscopy (SEM) showed that AZO crystallites, mainly spherical or quasi-spherical, formed toroidal grains with filled centers. Eu-doping promoted greater grain segregation and size, leading to toroidal morphologies with hollow centers. Photoluminescence (PL) spectroscopy revealed emission bands from 360–700 nm, with strong UV emissions at 378 and 389 nm linked to band-to-band and excitonic transitions. Weaker peaks at 366, 538, and 640 nm in the visible region were attributed to structural defects and impurities, while a 420 nm shoulder linked to interstitial zinc decreased with Eu-doping.

In this work a finite element analysis was performed on a geometry of an electrothermal micro actuator, to predict their displacement under a voltage with different material, the first material is the base material polysilicon and the second is a new compound Half Heusler whose characteristics are computed employing full-potential linearized augmented-plane wave (FP-LAPW) relied on density functional theory (DFT) as embedded in Wien2K. We considered the generalized gradient approximation (GGA-WC), and we took advantage of both the Gibbs and BoltzTrap codes to determine the thermal and transport properties for Half Heusler. Also, we used the Slack formula to determine the lattice thermal conductivity of the complex FeAsNb. Our research demonstrates that when using our Half Heusler compound as the material, the actuator responds better than when using Polysilicon.

This work presents a thorough analysis of the electronic, optical, and thermodynamic characteristics of ferromagnetic manganese selenide (MnSe) in both zinc-blende and rock-salt phases. Utilizing plane wave pseudo-potential calculations within the framework of spin-polarized density functional theory, our analysis offers a comprehensive evaluation. The calculated lattice parameters demonstrate a high level of concordance with available experimental data. Our findings indicate that MnSe compounds are semiconductors, as determined by their electronic band structures and density of states. Significant observations include the reduction in magnetic moments under increasing pressure, up to 10 GPa. Furthermore, we provide a detailed analysis of energy-dependent linear optical functions, including the complex dielectric function, complex refractive index, and reflectivity, and discuss their implications. Along with providing forecasts and in-depth discussions, our work clarifies the dependency of several thermodynamic variables on temperature and pressure for the compounds under investigation, including the bulk modulus, heat capacity, and thermal expansion coefficient.

Bismuth telluride selenide (Bi₂Te_2.7Se_0.3) is a commonly used n-type material for near room temperature thermoelectric applications. Synthesising Bi₂Te_2.7Se_0.3 (BTS) composites for the improvement in the thermoelectric performance has gained interest in recent years. In this work, BTS and BTS/reduced graphene oxide (BTS-X wt %, X = 0–9) materials were synthesised by mechanical alloying using a ball mill. Graphite was chemically transformed into graphene oxide (GO) and then subsequently reduced to reduced graphene oxide (rGO). We report that addition of a small quantity of rGO (X ≤ 5 wt %) into Bi₂Te_2.7Se_0.3 improved the thermoelectric performance by improving the charge carrier transport and suppressing the thermal transport at the BTS/rGO interface. Enhanced phonon scattering at the interface reduced the thermal conductivity to ~1.83 W/m K and improved the power factor ~2927 µW m^–1 K^–2 at 514 K for BTS-5 wt % rGO sample. The peak ZT (ZT_max) of ~0.82 at 514 K was obtained for the BTS-5 wt % rGO composite sample enhancing the peak ZT by ~14% from the pristine. Meanwhile, we observed the ZT average increases from ~0.55 (300–600 K) for BTS to ~0.75 (300–600 K) for BTS-5 wt % rGO sample. This improvement is mainly attributed to the improvement in the Seebeck coefficient and the reduction in the thermal conductivity of the composite material. Furthermore, the addition of rGO into BTS results into the improvement in the hardness of the composite material.

Pyrochlores have gained significant attention in contemporary scientific research owing to their distinctive optical properties, rendering them highly efficient across a broad spectrum of photocatalytic applications such as water remediation. Bi₂Ti₂O₇ nanopowder with a pyrochlore structure is successfully synthesized through a hybrid approach combining co-precipitation and the Pechini method. The influence of this hybrid synthesis technique on the photocatalytic activity of pure Bi₂Ti₂O₇ nanopowder is extensively studied. X-ray diffraction analysis established the pyrochlore structure of the synthesized Bi₂Ti₂O₇ nanopowder with well-defined diffraction peaks. The average crystallite size is estimated to be about 16 nm. Fourier transform infra-red spectroscopy insights the functional groups present, with wavenumbers at 489 and 1380 cm^–1 corresponding to the vibrations of Bi–O bonds, and at 621 cm^–1 associated with Ti–O–Ti stretching vibrations, further substantiating the formation of Bi₂Ti₂O₇ pyrochlore. UV-Vis spectroscopy reveals a narrow bandgap of 2.72 eV, ideal for efficient photocatalytic activity under visible light. The photoluminescence spectrum demonstrated the lower charge carrier recombination rate, which influences photocatalytic performance. Insights into the photocatalytic activity of Bi₂Ti₂O₇ is acquired through the degradation of a methylene blue dye under visible light (>420 nm). The maximum degradation was achieved within a brief period of 50 min with the apparent reaction rate constant of the catalyst 12.3 × 10^–3 min^–1. These findings highlight the potential of Bi₂Ti₂O₇ as a promising photocatalyst for a wide range of environmental applications, including wastewater treatment and the removal of organic pollutants.