Journal of Materials Science: Materials in Electronics最新文献

Gd-doped Ba_1-xGd_xCo₂Fe₁₆O₂₇ (BG_xCF) x = (0.00, 0.05, 0.10, 0.15, 0.20, and 0.25) wt.% W-type hexaferrite ceramic pellets were synthesized by ball milling solid-state reaction technique. XRD patterns of the prepared samples verify the single-phase polycrystalline nature without any impurity phase. The doping of Gd ions in the samples impacted the lattice parameters, unit cell volume and bulk density increases. Morphological results analysis using SEM shows the hexagonal plate-like structure of the BG_xCF particles. The increase of Gd contents in the samples created multi-domain structure and grain growth occurred. FT-IR analysis confirmed the existence of the octahedral and tetrahedral vibration of Fe–O, with Gd substitution bond strength between the atom decreases. Raman analysis verifies the existence of A_1g, E_1g and E_2g Raman modes, with Gd wt.% increases there is a red shift of the vibration modes. Magnetic results reveal that with Gd substitution in the BG_xCF samples, the magnetization saturation (M_s) increased for x = 0.05, and 0.10 samples due to strain magnetization, while, for x = 0.15 and 0.20 samples, Ms decreased due to the spinning by Gd ions, and but it is increased for x = 0.25 samples. Moreover, with increases of Gd wt.% in the samples, there is a decrease in the coercive field due to the increase of particle size and a decrease of magnetocrystalline anisotropy. In addition, the dielectric properties revealed increases in both permittivity and dielectric loss with the Gd contents in BG_xCF samples. Permeability studies show the existence of spin resonance phenomena in the samples. The magnetic losses in the Gd-doped samples are higher than the undoped sample due to the decreases of magnetocrystalline anisotropy. The highest values of both dielectric and magnetic losses of the Gd-doped BG_xCF samples make these materials enhance its performance in microwave potential devices applications.

Lattice-matched InAs/GaAs_0.08Sb_0.92 superlattices were grown on InAs substrates via metalorganic vapor-phase epitaxy, and the excitation intensity dependence of photoluminescence (PL) was measured from 20 to 300 K. The observed spectra were compared with the calculated spontaneous emission transitions. At 20 K, the changes in the calculated and measured spectral shapes with the carrier density in the wells closely concur. The blue shift of the emission peak, as the excitation intensity increased, was due to emission from a higher-order band. We determined the specific wavelengths at which the luminescence intensity increased rapidly at certain excitation intensities. These results broaden the spectral range. At 300 K, the PL spectrum was obtained only under strong excitation. Furthermore, higher-order transitions were also dominant in this case.

This study presents a detailed investigation into the synthesis and characterization of Europium (Eu)-doped Sr₂FeTiO₆ [Sr_2−xEu_xFeTiO₆ (x = 0, 0.5)] double perovskite compounds, aimed at enhancing the understanding of their structural, optical, magnetic, and dielectric properties. Using high-temperature solid-state reactions, single-phase compounds were successfully synthesized, as confirmed by X-ray diffraction (XRD) and Rietveld refinement, revealing a stable cubic crystal structure. X-ray photoelectron spectroscopy (XPS) verified the oxidation states of the constituent elements, while optical studies demonstrated a significant reduction in the energy band gap from 2.92 to 2.26 eV with Eu doping. Magnetically, the undoped Sr₂FeTiO₆ compound exhibited weak ferromagnetism with canted spins and pronounced magnetic anisotropy. In contrast, Eu doping induced a transition to antiferromagnetic-like behavior, with a notable decrease in magnetization, coercivity, and anisotropy. The dielectric properties were also enhanced with increasing Eu content, as evidenced by the progressive increase in dielectric constant. The novelty of this research lies in the comprehensive exploration of the Eu-doped Sr₂FeTiO₆ system, demonstrating the tunability of its magnetic and electronic properties through rare-earth doping. These findings highlight the potential of Sr_2–xEu_xFeTiO₆ compounds for advanced applications in electronic, magneto-optical, and optoelectronic devices, contributing significantly to the field of functional perovskite materials.

Wearable heating textiles are increasingly popular for thermotherapy applications; however, ensuring their durability and comfort presents a significant challenge in design and material selection. Herein, rib-knitted heating fabrics were modified in the active regions by adjusting knitting structural parameters, including knit, float, and tuck stitches. Four sample types were fabricated: 3R (three courses of knit), 3F (three courses of float), 3 T (three courses of tuck), and FTF (first-course float, second-course tuck, third-course float), using stainless steel and cotton yarns. The durability and comfort properties of these knitted heating textiles, tailored for wearable heating textiles, were evaluated. The 3F sample exhibited the highest thermal resistance, air permeability, and water vapor permeability due to its structural characteristics. Moreover, after six washing cycles, surface temperature reductions of 10.31% (3R), 12.21% (3 T), 8.85% (3F), and 9.12% (FTF) were recorded. Bending cycles, perspiration, and detergent exposure showed no notable effects. However, in the 3 T structure, loosely bound fibers resulted in significant fiber breakage, leading to an 8.92% temperature change following 5000 abrasion cycles.

The practical limitation of using rhombohedral-structured hematite (α-Fe₂O₃) system in semiconductor industry is its poor electrical conductivity (~ 10^–11 S/m). On the other hand, hematite is a potential candidate for solar cell and hydrogen storage applications. This stimulates a worldwide interest for enhancing electrical conductivity in hematite based materials. The co-doping of divalent Co and tetravalent Ti ions in the hematite structure has remarkably enhanced electrical conductivity up to the order of 10^–2 S/m and promised a wide scope of electronic applications of the materials. The variation of co-doping content (x) and heat treatment environment under air and vacuum played a crucial role for enhancement of electrical conductivity. The material of composition α-Fe_2−xTi_x/2Co_x/2O₃ with x = 0.2, 0.4 and 0.6 has been stabilized in rhombohedral phase by mechanical alloying and post heat treatment at 1000 °C. The current–voltage characteristics of the samples have been measured in the temperature range of 313–723 K. This work has studied the mechanisms of temperature- and applied voltage- dependent electrical properties in Co and Ti co-doped α-Fe₂O₃ system. The experimental results of tuning electrical conductivity and electro-resistance can be useful for applications of hematite based metal oxides in modern spintronic devices, gas sensors, memory devices and thermoelectric devices.

The multiferroic composites xCoNd_0.1Fe_1.9O₄—(1-x) Pb_0.97Yb_0.03Zr₀.₅₂Ti_0.48O₃ (x = 0.02, 0.05 and 0.07) were analysed to investigate their dielectric and optical properties. Variations in dielectric properties with respect to frequency and temperature exhibited improvement with an increase in ferrite content in the composites. Impedance analysis of the samples highlighted the influence of grain and grain boundary effects on the electrical properties. Photoluminescence studies revealed a decrease in PL intensity as the ferrite content increased. FTIR analysis confirmed the connectivity and interfacial interactions between the two parent ferroic phases within the composites. These findings underscore the significance of the prepared materials for potential device applications.

The ultrasonic spray method was applied to investigate fluorine-doped zinc oxide thin films on glass substrate at 420 °C, with different fluorine doping rates ranging from 0 to 5 at%. This study presents a new description of the relationship linking the electrical conductivity to the optical band gap with various fluorine doping levels. It was found that all films exhibited high electrical conductivity values. The highest electrical conductivity was found equal to 169 (Ωcm)⁻¹; this was obtained for the 5 at% doping level. Moreover, it turned out that the optical band gap dropped from 3.39 to 3.28 eV as the fluorine doping level augmented. The correlation between the electrical and optical properties and the doping level suggests that the optical band gap and fluorine doping level have a significant impact on the electrical conductivity of the thin films under consideration. In addition, the equation correlating the electrical conductivity and the doping level gave a maximum error of about 4% for fluorine-doped zinc oxide for a concentration of 3 at%. However, the experimental results for the correlation between the electrical conductivity and the fluorine doping level of ZnO films turned out to be invariable.

Eu₂O₃-doped oxychloride tellurite glasses were fabricated, and their luminescent characteristics were investigated for glass scintillators. Luminescent peaks originating from the transition between 4f energy levels of Eu³⁺ were observed at 577, 592, 612, 652, and 701 nm under 530 nm light. These luminescent peaks were also observed when irradiated with X-ray, and the maximum intensity was observed at a Eu₂O₃ concentration of 3.0%. Furthermore, scintillation decay times of about 0.64 ms were detected from the Eu₂O₃-doped oxychloride tellurite glasses. Moreover, the 3.0% Eu₂O₃-doped oxychloride tellurite glass exhibited the lowest afterglow level (177 ppm) that was lower than that of a Tl-doped CsI single crystal.

Nitrogen-doped zinc oxide (N:ZnO) thin films were deposited on glass substrates via radio frequency (RF) magnetron sputtering and subsequently annealed at 300 °C, 400 °C, 500 °C, and 600 °C to assess their viability and stability as transparent conductive oxide (TCO) materials. Structural and compositional analyses were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). XRD analysis revealed preferential crystallite orientations along the (100), (002), (101), and (110) planes. Atomic force microscopy (AFM) measurements indicated particle sizes two to four times larger than those derived from XRD, suggesting a sub-granular internal structure, as XRD probes coherently diffracting domains. XPS analysis of the N 1 s spectra identified two distinct peaks at approximately 397 eV and 407.5 eV, indicating nitrogen incorporation into the ZnO matrix. Photoluminescence spectroscopy revealed that nitrogen doping induced the formation of interstitials and defects associated with oxygen and zinc vacancies. Optical measurements showed that the (N:ZnO) thin films exhibited an average optical band gap of approximately 3.1 eV, with 80% transmittance in the visible spectrum. A linear relationship was observed between the band gap energy and the tail width. Except for the film annealed at 600 °C, all annealed films showed a reduction in peak photoluminescence intensity with increasing annealing temperature. Finally, no significant changes in the electrical performance of the p-N/n-Si diode were observed as a result of annealing-induced surface modifications. The results provide valuable insights into the optimization of (N:ZnO) thin films for use in international optoelectronic and photovoltaic research, where advancements in TCOs are critical for the development of high-performance, sustainable technologies.

The correspondence between sensitivity and adsorption/desorption-induced hysteresis in ZnSnO₃ resistive sensors is investigated. The ZnSnO₃ humidity sensor made at 100 °C present lower degree of error (1.21 ± 0.12%RH) associated with sensitivity of 0.11 ± 0.01 kΩ(%RH)⁻¹, whereas the 500 °C annealed analogous showed an increased degree of measurement error value (1.48 ± 0.23% RH) along with sensitivity of 0.14 ± 0.02 kΩ(%RH)⁻¹ within the humidity range of 8–97% RH. A proportionate increase in sensitivity and measurement error is evident with increase in annealing temperature. The variance of principal components (PC1 and PC2) contributes 89.92% and 4.64% in the score plot confirms the migration of measurement errors from high to low RH level subject to annealing of sensing material according to principal component analysis (PCA). The trade-off relation between sensitivity and measurement error is observed for sensors with enactment of annealing emphasizes the prominence of revising the adsorption/desorption hysteresis as an crucial feature in development of metal oxide-based chemiresistive sensors.