Physics of the Solid State最新文献

A low-cost polyol synthesis route was used to prepare Y₂Zr₂O₇ (YZO) phosphors doped with Bi³⁺ (1–2.5 at %) and co-doped with Tb³⁺ (1–3 at %). The structural, morphological, and optical properties were characterized using XRD, FESEM, UV-Vis, and PL spectroscopy. The Rietveld refinement of the XRD patterns confirmed that the undoped YZO host crystallizes in a cubic pyrochlore structure with the Fd({{bar {3}}})m space group. The FESEM images revealed agglomerated granule-like particles with an average size of ~105 nm. The UV-Vis absorption spectra showed characteristic peaks of Bi³⁺ and Tb³⁺ ions. The Photoluminescence studies demonstrated a blue emission at ~430 nm from the Bi³⁺ (³P₁ → ¹S₀ transition) under 305 nm excitation, with an optimal composition of YZO:1.5% Bi³⁺. Further, Co-doping with Tb³⁺ and exciting at 225 nm produced weak blue emissions and a dominant green emission at 545 nm from the ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions. The optimal composition of the phosphor sample is identified to be Y_1.965Zr₂O₇:1.5% Bi³⁺, 2% Tb³⁺ which exhibits tunable blue–green emissions supported by lifetime decay analysis and energy transfer between Bi³⁺ and Tb³⁺ ions. The CIE chromaticity coordinates indicate its potential for display applications.

The strontium calcium titanate (Sr_1–xCa_xTiO₃) ceramics have been synthesized using the solid-state reaction method. Sr_1–xCa_xTiO₃ ceramics are sintered at 1300°C for 3 h. The X-ray diffraction confirmed perovskite tetragonal strontium calcium titanate ceramics. It is found that with the increase of calcium content in Sr_1–xCa_xTiO₃ the unit cell volume and density decrease. The microstructure of strontium calcium titanate is examined using field emission scanning electron microscopy it is found that with the addition of calcium, the average grain size has increased for all compositions of Sr_1–xCa_xTiO₃ ceramics. Porosity is decreased with the addition of calcium in Sr_1–xCa_xTiO₃ ceramics. The variation of relative permittivity (ɛ_r) and loss tangent (tanδ) with temperature in Sr_1–xCa_xTiO₃ ceramics was observed to remain constant up to 200°C and beyond this temperature ɛ_r and tan δ enhanced with a rise in Calcium content.

LiMn₂O₄ is well established material used in Li-ion batteries as cathode. To widen the application capability, it is important to tune its electrical properties using various approaches such as doping with suitable elements. The present study explores the fabrication of LiMn₂O₄ and LiMn_1.94Gd_0.03Fe_0.03O₄ nano powders along with their ceramic pellets. The X-ray diffraction was employed to study the crystalline purity and scanning electron micrograph is utilized to study the size and shape of the nanoparticles. The real and imaginary parts of the impedance from 10² to 10⁶ Hz. The equivalent circuit is simulated to understand the microscopic origins to the measured impedance. Finally, the ac conductivity was calculated from impedance data and analyzed using power law of conductivity. The universal exponent (s-parameter) was obtained from the linear fit curve of the frequency dependent conductivity. Hence, these samples may bring new developments in the fields of cathode materials for Li-ion materials.

The NiO films exhibit excellent optical and electrical properties due to their wide bandgap and p‑type semiconducting behaviour, making them suitable for optoelectronic and TCOs. Furthermore, the intrinsic properties of NiO are enhanced by doping with suitable elements. Pristine and Gd-doped NiO (Ni_1–xGd_xO; x = 0, 0.02, 0.04, and 0.06) films. The various doping concentrations are deposited using the spin deposition technique. The detailed effects of Gadolinium (Gd) doping in a NiO matrix are investigated using structural, optical, and photoluminescence analysis. The XRD results show the average crystallite size varying from 14 to 8.7 nm for pure and Gd-doped NiO films with a face-centred cubic polycrystalline nature. The Raman spectroscopy analysis confirms the quality (purity) of the prepared thin films, showing Ni–O first-order modes that shift to higher wave numbers with Gd doping. FTIR analysis exhibits Ni–O-related vibrational bands in the range of 555 to 735 cm^–1 and other vibrational bands linked to various functional groups. The UV-visible spectra reveal the highest average transmittance of around 90% for films with Gd doping up to 4%. The energy gap evaluated utilizing Tauc’s plot analysis, varies from 3.52 to 3.56 eV for pure and doped films. From the PL spectra, near band edge emission peaks (363 nm) and other structural defects-related emission peaks are observed. The results suggest that by varying the dopant concentration, the structural and optical parameters can be modified. These films have the potential to be used in optoelectronic and catalytic devices.

Controlled doping is the paradigmatic approach for improving the properties of any pristine material. Ni_xMn_1–xFe₂O₄ (x = 0, 0.01, 0.03, 0.05, 1) were synthesized by the facile sol–gel auto combustion method. The as-prepared samples were further annealed. Formation of impurity levels, structural, morphological, vibrational, optical and electronic variations as a result of Nickel doping is systematically analyzed by structural and optical studies. The average crystallite size shows decremental trend for pre annealed and an incremental trend for annealed samples. Increased particle agglomeration can be seen in SEM micrographs. EDAX confirms the compositional variation of Nickel from 1 to 5%. FTIR and Raman spectra represent band shifting towards higher wavenumber and Raman peak broadening with Nickel substitution. Optical analyses suggests that MnFe₂O₄ which has optical bandgap of ~2.2 eV is reduced to ~1.7 eV (pre annealed) and ~1.4 eV (annealed) and thus can be made as a photo catalyst material. Photoluminescence spectra of pre- and post-annealed samples show presence of peak in visible region with a red shift in PL spectra indicating band narrowing.

This study presents the synthesis and modification of Fe₂O₃ nanoparticles using a simple co-precipitation method, followed by microwave irradiation and incorporation with activated charcoal to enhance their structural, optical, and electrochemical properties. X-ray diffraction (XRD) analysis confirmed the rhombohedral phase of hematite (α-Fe₂O₃) and revealed enhanced lattice strain upon microwave irradiation improving active site density. UV-Vis spectroscopy showed a significant bandgap reduction from 2.5 eV (pure Fe₂O₃) to 1.6 eV (microwave-irradiated Fe₂O₃ with activated charcoal) indicating superior light absorption. Electrochemical characterization demonstrated improved redox activity and specific capacitance, with microwave-irradiated Fe₂O₃ with activated charcoal achieving the highest performance due to enhanced conductivity and porosity. These results highlight the synergistic effects of microwave irradiation and activated charcoal making the modified Fe₂O₃ a promising candidate for applications in catalysis, energy storage, and optoelectronics.

The barium strontium titanate (Ba_1–xSr_xTiO₃) ceramics have been synthesized using the solid-state reaction method. Ba_1–xSr_xTiO₃ ceramics are sintered at 1000°C for 3 h. The X-ray diffraction confirmed perovskite tetragonal barium strontium titanate ceramics. It is found that with the increase of strontium content in Ba_1–xSr_xTiO₃ the unit cell parameters, dielectric loss decreased. The microstructure of barium strontium titanate is examined using field emission scanning electron microscopy it is found that with the addition of strontium, the average grain size has decreased for all compositions of Ba_1–xSr_xTiO₃ ceramics. Curie temperature is decreased with the addition of strontium in Ba_1–xSr_xTiO₃ ceramics. The variation of relative permittivity (ɛ_r) and loss tangent (tanδ) with temperature of Ba_1–xSr_xTiO₃ ceramics was studied.

Indium gallium nitride (InGaN) solar cells have emerged as promising candidates in photovoltaic research due to their tunable direct bandgap, strong light absorption, and favorable electronic characteristics. This study presents a numerical analysis of a p-InGaN/n-InGaN solar cell configuration, both with and without an added back surface field (BSF) layer, using the SILVACO-ATLAS 2D device simulation tool. The basic solar cell structure without a BSF layer (Al//p-InGaN/n-InGaN/Ag) serves as a reference, while a highly doped indium nitride (InN) BSF layer at the rear contact interface contact in the enhanced version. The study explores how variations in the BSF layer, in addition to the thickness and doping levels of the buffer and absorber layers, influence on key performance metrics such as open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), power conversion efficiency (PCE), and quantum efficiency (QE). Findings reveal that the introduction of the InN BSF layer improves the PCE from 23.52 to 24.43%, with a corresponding rise in JSC from 36.91 to 38.05 mA/cm², and VOC from 0.817 to 0.821 V. Furthermore, the quantum efficiency exceeds 78.32% over the 300–900 nm wavelength range. This work provides a comprehensive optimization approach and demonstrates that using an InN BSF layer can significantly enhance the efficiency of InGaN solar cells by mitigating recombination and improving carrier collection. The findings offer a pathway toward higher-efficiency InGaN-based solar cells, making this approach a promising candidate for future photovoltaic technologies in both terrestrial and space applications.

A series of white emitting phosphors based Ce_1–xDy_xMgAl₁₁O₁₉ (x = 0.01–0.05) were synthesized by solid state chemistry. The systematic studies of the luminescent properties of these phosphors were performed. It is established that the (Ce_0.92Dy_0.02)MgAl₁₁O₁₉ (CMAD) is crystallizes in hexagonal crystal sys-tem with P63/mmc (194) space group and its unit cell parameters are a = 5.4037 Å, b = 5.4037 Å, c = 21.9296 Å; α = 90.00°, β = 90.00°, γ = 120.00°; Z = 2; V = 587.41 (Å)³. SEM technique was used elucidate the surface morphology and particle sizes of CMAD. The excitation spectra reveal that the UV-Vis light efficiently excite Ce_1–xDy_xMgAl₁₁O₁₉ in the range 220–400 nm. The emission spectrum of (Ce_0.98Dy_0.02)MgAl₁₁O₁₉ shows two strong peaks at 474 and 570 nm as well as weak bands at 657, 696, and 750 nm. The luminescence decay time (τ) was calculated and found 1.22 ms.

In conjunction with particle swarm optimisation techniques, we have delved into the crystal structure of low boron Sc–B compounds within 100 GPa. The trigonal Sc₂B with space group P-3m1 is consistently stable over a pressure range of 0–100 GPa. Moreover, this P-3m1-Sc₂B structure is mechanically and dynamically stable, as evidenced by elastic constant and phonon dispersion curve calculations. The hexagonal ScB with space group P-6m2 is always stable in the pressure region 0–92.6 GPa. Structurally, the B atoms of the structure form a separate layer that is stacked alternately with the Sc layer along the c direction, and at high pressures it changes phase to an orthorhombic Fmmm structure. Interestingly, calculations of elastic constants and hardness show that both phases of Sc₂B and ScB have high hardness values at ambient pressure, especially P-6m2-ScB, which unexpectedly reaches a hardness value of 26.8 GPa, an incompressible material.