Development and Fabrication of a Multi-Layer Planar Solar Light Absorber Achieving High Absorptivity and Ultra-Wideband Response from Visible Light to Infrared.

The objective of this study is to create a planar solar light absorber that exhibits exceptional absorption characteristics spanning from visible light to infrared across an ultra-wide spectral range. The eight layered structures of the absorber, from top to bottom, consisted of Al2O3, Ti, Al2O3, Ti, Al2O3, Ni, Al2O3, and Al. The COMSOL Multiphysics® simulation software (version 6.0) was utilized to construct the absorber model and perform simulation analyses. The first significant finding of this study is that as compared to absorbers featuring seven-layered structures (excluding the top Al2O3 layer) or using TiO2 or SiO2 layers as substituted for Al2O3 layer, the presence of the top Al2O3 layer demonstrated superior anti-reflection properties. Another noteworthy finding was that the top Al2O3 layer provided better impedance matching compared to scenarios where it was absent or replaced with TiO2 or SiO2 layers, enhancing the absorber's overall efficiency. Consequently, across the ultra-wideband spectrum spanning 350 to 1970 nm, the average absorptivity reached an impressive 96.76%. One significant novelty of this study was the utilization of various top-layer materials to assess the absorption and reflection spectra, along with the optical-impedance-matching properties of the designed absorber. Another notable contribution was the successful implementation of evaporation techniques for depositing and manufacturing this optimized absorber. A further innovation involved the use of transmission electron microscopy to observe the thickness of each deposition layer. Subsequently, the simulated and calculated absorption spectra of solar energy across the AM1.5 spectrum for both the designed and fabricated absorbers were compared, demonstrating a match between the measured and simulated results.

Investigations of In2O3 Added SiC Semiconductive Thin Films and Manufacture of a Heterojunction Diode.

This study involved direct doping of In2O3 into silicon carbide (SiC) powder, resulting in 8.0 at% In-doped SiC powder. Subsequently, heating at 500 °C was performed to form a target, followed by the utilization of electron beam (e-beam) technology to deposit the In-doped SiC thin films with the thickness of approximately 189.8 nm. The first breakthrough of this research was the successful deposition of using e-beam technology. The second breakthrough involved utilizing various tools to analyze the physical and electrical properties of In-doped SiC thin films. Hall effect measurement was used to measure the resistivity, mobility, and carrier concentration and confirm its n-type semiconductor nature. The uniform dispersion of In ions in SiC was as confirmed by electron microscopy energy-dispersive spectroscopy and secondary ion mass spectrometry analyses. The Tauc Plot method was employed to determine the Eg values of pure SiC and In-doped SiC thin films. Semiconductor parameter analyzer was used to measure the conductivity and the I-V characteristics of devices in In-doped SiC thin films. Furthermore, the third finding demonstrated that In2O3-doped SiC thin films exhibited remarkable current density. X-ray photoelectron spectroscopy and Gaussian-resolved spectra further confirmed a significant relationship between conductivity and oxygen vacancy concentration. Lastly, depositing these In-doped SiC thin films onto p-type silicon substrates etched with buffered oxide etchant resulted in the formation of heterojunction p-n junction. This junction exhibited the rectifying characteristics of a diode, with sample current values in the vicinity of 102 mA, breakdown voltage at approximately -5.23 V, and open-circuit voltage around 1.56 V. This underscores the potential of In-doped SiC thin films for various semiconductor devices.

Analysis of an Ultra-Wideband, Perfectly Absorptive Fractal Absorber with a Central Square Nanopillar in a Cylindrical Structure with a Square Hollow.

In this study, a fractal absorber was designed to enhance light absorptivity and improve the efficiency of converting solar energy into electricity for a range of solar energy technologies. The absorber consisted of multiple layers arranged from bottom to top, and the bottom layer was made of Ti metal, followed by a thin layer of MgF2 atop it. Above the two layers, a structure comprising square pillars formed by three layers of Ti/MgF2/Ti was formed. This pillar was encompassed by a square hollow with cylindrical structures made of Ti material on the exterior. The software utilized for this study was COMSOL Multiphysics® (version 6.0). This study contains an absorption spectrum analysis of the various components of the designed absorber system, confirming the notion that achieving ultra-wideband and perfect absorption resulted from the combination of the various components. A comprehensive analysis was also conducted on the width of the central square pillar, and the analysis results demonstrate the presence of several remarkable optical phenomena within the investigated structure, including propagating surface plasmon resonance, localized surface plasmon resonance, Fabry-Perot cavity resonance, and symmetric coupling plasma modes. The optimal model determined through this software demonstrated that broadband absorption in the range of 276 to 2668 nm, which was in the range of UV-B to near-infrared, exceeded 90.0%. The average absorption rate in the range of 276~2668 nm reached 0.965, with the highest achieving a perfect absorptivity of 99.9%. A comparison between absorption with and without outer cylindrical structures revealed that the resonance effects significantly enhanced absorption efficiency, as evidenced by a comparison of electric field distributions.

Fabrications of the Flexible Non-Enzymatic Glucose Sensors Using Au-CuO-rGO and Au-CuO-rGO-MWCNTs Nanocomposites as Carriers.

A flexible, non-enzymatic glucose sensor was developed and tested on a polyethylene terephthalate (PET) substrate. The sensor's design involved printing Ag (silver) as the electrode and utilizing mixtures of either gold-copper oxide-modified reduced graphene oxide (Au-CuO-rGO) or gold-copper oxide-modified reduced graphene oxide-multi-walled carbon nanotubes (Au-CuO-rGO-MWCNTs) as the carrier materials. A one-pot synthesis method was employed to create a nanocomposite material, consisting of Au-CuO-rGO mixtures, which was then printed onto pre-prepared flexible electrodes. The impact of different weight ratios of MWCNTs (0~75 wt%) as a substitute for rGO was also investigated on the sensing characteristics of Au-CuO-rGO-MWCNTs glucose sensors. The fabricated electrodes underwent various material analyses, and their sensing properties for glucose in a glucose solution were measured using linear sweep voltammetry (LSV). The LSV measurement results showed that increasing the proportion of MWCNTs improved the sensor's sensitivity for detecting low concentrations of glucose. However, it also led to a significant decrease in the upper detection limit for high-glucose concentrations. Remarkably, the research findings revealed that the electrode containing 60 wt% MWCNTs demonstrated excellent sensitivity and stability in detecting low concentrations of glucose. At the lowest concentration of 0.1 µM glucose, the nanocomposites with 75 wt% MWCNTs showed the highest oxidation peak current, approximately 5.9 µA. On the other hand, the electrode without addition of MWCNTs displayed the highest detection limit (approximately 1 mM) and an oxidation peak current of about 8.1 µA at 1 mM of glucose concentration.

Synthesis of ZnO Nanoflower Arrays on a Protrusion Sapphire Substrate and Application of Al-Decorated ZnO Nanoflower Matrix in Gas Sensors.

In this study, we utilized a sapphire substrate with a matrix protrusion structure as a template. We employed a ZnO gel as a precursor and deposited it onto the substrate using the spin coating method. After undergoing six cycles of deposition and baking, a ZnO seed layer with a thickness of 170 nm was formed. Subsequently, we used a hydrothermal method to grow ZnO nanorods (NRs) on the aforementioned ZnO seed layer for different durations. ZnO NRs exhibited a uniform outward growth rate in various directions, resulting in a hexagonal and floral morphology when observed from above. This morphology was particularly evident in ZnO NRs synthesized for 30 and 45 min. Due to the protrusion structure of ZnO seed layer, the resulting ZnO nanorods (NRs) displayed a floral and matrix morphology on the protrusion ZnO seed layer. To further enhance their properties, we utilized Al nanomaterial to decorate the ZnO nanoflower matrix (NFM) using a deposition method. Subsequently, we fabricated devices using both undecorated and Al-decorated ZnO NFMs and deposited an upper electrode using an interdigital mask. We then compared the gas-sensing performance of these two types of sensors towards CO and H2 gases. The research findings indicate that sensors based on Al-decorated ZnO NFM exhibit superior gas-sensing properties compared to undecorated ZnO NFM for both CO and H2 gases. These Al-decorated sensors demonstrate faster response times and higher response rates during the sensing processes.

Comparison of the Degradation Effect of Methylene Blue for ZnO Nanorods Synthesized on Silicon and Indium Tin Oxide Substrates.

In the context of ZnO nanorods (NRs) grown on Si and indium tin oxide (ITO) substrates, this study aimed to compare their degradation effect on methylene blue (MB) at different concentrations. The synthesis process was carried out at a temperature of 100 °C for 3 h. After the synthesis of ZnO NRs, their crystallization was analyzed using X-ray diffraction (XRD) patterns. The XRD patterns and top-view SEM observations demonstrate variations in synthesized ZnO NRs when different substrates were used. Furthermore, cross-sectional observations reveal that ZnO NRs synthesized on an ITO substrate exhibited a slower growth rate compared to those synthesized on a Si substrate. The as-grown ZnO NRs synthesized on the Si and ITO substrates exhibited average diameters of 110 ± 40 nm and 120 ± 32 nm and average lengths of 1210 ± 55 nm and 960 ± 58 nm, respectively. The reasons behind this discrepancy are investigated and discussed. Finally, synthesized ZnO NRs on both substrates were utilized to assess their degradation effect on methylene blue (MB). Photoluminescence spectra and X-ray photoelectron spectroscopy were employed to analyze the quantities of various defects of synthesized ZnO NRs. The effect of MB degradation after 325 nm UV irradiation for different durations can be evaluated using the Beer-Lambert law, specifically by analyzing the 665 nm peak in the transmittance spectrum of MB solutions with different concentrations. Our findings reveal that ZnO NRs synthesized on an ITO substrate exhibited a higher degradation effect on MB, with a rate of 59.5%, compared to NRs synthesized on a Si substrate, which had a rate of 73.7%. The reasons behind this outcome, elucidating the factors contributing to the enhanced degradation effect are discussed and proposed.

Synthesis of ZnO Nanoflower Arrays on Patterned Cavity Substrate and Their Application in Methylene Blue Degradation.

A novel method was proposed to fabricate a ZnO seed layer with a protrusion and matrix structure, and then ZnO nanorods could be synthesized on it using the hydrothermal method to form ZnO nanoflower arrays (NFAs) easily. A patterned sapphire with a matrix cavity was used as the template, ZnO gel was deposited on the multilayer substrates using spinning coating, and the prepared seed layer with a protrusion and an array-patterned structure was moved to a Si substrate using the lift-off method. Because the ZnO seed layer exhibited a matrix and protrusion structure, ZnO nanorods were grown vertically downwards and formed ZnO NFAs. The XRD patterns resulting from analyses showed that the diffraction peaks of the five growth directions of ZnO NFAs increased as growth time increased. Furthermore, SEM and FIB analyses indicated that the length, width, aspect ratio, and total surface area of ZnO NFAs grown on the transferred seed layer increased as the synthesis time increased. Different ZnO NFAs synthesized for varying synthesis times were used to investigate methylene blue degradation, with the effect of ZnO NFAs on methylene blue degradation determined using the Beer-Lambert law. Our results demonstrate that the effect of ZnO NFAs on methylene blue degradation was enhanced with increasing synthesis time.

Investigations of Photoluminescence Properties of CaxMg2-xSi2O6:yEu2+ (x = 0.5-1.25, y = 0.015-0.035) Phosphors.

Previously, there were almost no relevant studies on developing the optimal CaxMg2-xSi2O6:yEu2+ phosphor composition for its finest optical properties. This study employs two steps to determine the optimal composition for CaxMg2-xSi2O6:yEu2+ phosphors. First, CaMgSi2O6:yEu2+ (y = 0.015, 0.020, 0.025, 0.030, 0.035) was used as the primary composition of specimens synthesised in a reducing atmosphere of 95% N2 + 5% H2 to investigate the effect of Eu2+ ions on the photoluminescence properties of each variant. The emission intensities of the entire photoluminescence excitation (PLE) and photoluminescence (PL) emission spectra of the CaMgSi2O6:yEu2+ phosphors initially increased as the concentration of the Eu2+ ions increased, peaking at y = 0.025. The cause of the variations across the entire PLE and PL spectra of all five CaMgSi2O6:yEu2+ phosphors was investigated. Because the CaMgSi2O6:0.025Eu2+ phosphor had the highest PLE and PL emission intensities, in the next step, CaxMg2-xSi2O6:0.025Eu2+ (x = 0.5, 0.75, 1.0, 1.25) was used as the primary composition to investigate the effect on the photoluminescence properties when the CaO content varied. We also show that the Ca content has an apparent effect on the photoluminescence properties of CaxMg2-xSi2O6:0.025Eu2+ phosphors, and the optimal phosphor composition is Ca0.75Mg1.25Si2O6:0.025Eu2+ because it has the largest PLE and PL values. X-ray diffraction (XRD) analyses of CaxMg2-xSi2O6:0.025Eu2+ phosphors were performed to identify the factors responsible for this outcome.

Investigation of a Multi-Layer Absorber Exhibiting the Broadband and High Absorptivity in Red Light and Near-Infrared Region.

In this study, an absorber with the characteristics of high absorptivity and ultra-wideband (UWB), which was ranged from the visible light range and near-infrared band, was designed and numerically analyzed using COMSOL Multiphysics® simulation software (version 6.0). The designed absorber was constructed by using two-layer square cubes stacked on the four-layer continuous plane films. The two-layer square cubes were titanium dioxide (TiO2) and titanium (Ti) (from top to bottom) and the four-layer continuous plane films were Poly(N-isopropylacrylamide) (PNIPAAm), Ti, silica (SiO2), and Ti. The analysis results showed that the first reason to cause the high absorptivity in UWB is the anti-reflection effect of top TiO2 layer. The second reason is that the three different resonances, including localized surface plasmon resonance, the propagating surface plasmon resonance, and the Fabry-Perot (FP) cavity resonance, are coexisted in the absorption peaks of the designed absorber and at least two of them can be excited at the same time. The third reason is that two FP resonant cavities were formed in the PNIPAAm and SiO2 dielectric layers. Because of the combination of the anti-reflection effect and the three different resonances, the designed absorber presented the properties of UWB and high absorptivity.

Research and Evaluation on an Optical Automatic Detection System for the Defects of the Manufactured Paper Cups.

In this paper, the paper cups were used as the research objects, and the machine vision detection technology was combined with different image processing techniques to investigate a non-contact optical automatic detection system to identify the defects of the manufactured paper cups. The combined ring light was used as the light source, an infrared (IR) LED matrix panel was used to provide the IR light to constantly highlight the outer edges of the detected objects, and a multi-grid pixel array was used as the image sensor. The image processing techniques, including the Gaussian filter, Sobel operator, Binarization process, and connected component, were used to enhance the inspection and recognition of the defects existing in the produced paper cups. There were three different detection processes for paper cups, which were divided into internal, external, and bottom image acquisition processes. The present study demonstrated that all the detection processes could clearly detect the surface defect features of the manufactured paper cups, such as dirt, burrs, holes, and uneven thickness. Our study also revealed that the average time for the investigated Automatic Optical Detection to detect the defects on the paper cups was only 0.3 s.

Synthesis and Luminescence Properties of Eu2+-Doped Sr3MgSi2O8 Blue Light-Emitting Phosphor for Application in Near-Ultraviolet Excitable White Light-Emitting Diodes.

In this study, [Sr0.99Eu0.01]3MgSi2O8 phosphors were sintered at 1200-1400 °C for 1-5 h by using the solid-state reaction method. The crystallinity and morphology of these phosphors were characterized through X-ray diffraction analysis and field-emission scanning electron microscopy, respectively, to determine their luminescence. The photoluminescence properties, including the excitation and emission properties, of the prepared phosphors were investigated through fluorescence spectrophotometry. The α-Sr2SiO4, Sr2MgSi2O7, and Sr3MgSi2O8 phases coexisted in the [Sr0.99Eu0.01]3MgSi2O8 phosphors, which were synthesized at low temperatures. The particles of these phosphors had many fine hairs on their surface and resembled Clavularia viridis, which is a coral species. Transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the fine hairs contained the Sr2SiO4 and Sr2MgSi2O7 phases. However, when the [Sr0.99Eu0.01]3MgSi2O8 phosphors were sintered at 1400 °C, the Sr3MgSi2O8 phase was observed, and the Eu2+-doped Sr3MgSi2O8 phase dominated the only broad emission band, which had a central wavelength of 457 nm (blue light). The emission peaks at this wavelength were attributed to the 4f65d1-4f7 transition at the Sr2+(I) site, where Sr2+ was substituted by Eu2+. The average decay time of the synthesized phosphors was calculated to be 1.197 ms. The aforementioned results indicate that [Sr0.99Eu0.01]3MgSi2O8 can be used as a blue-emitting phosphor in ultraviolet-excited white light-emitting diodes.

Investigations of a Statistical and Analytical Method to Find the Relationship between the Morphological and Optical Properties of ZnO Nanoflower Arrays.

In this study, a sapphire substrate with a patterned concave structure was used to prepare ZnO film/A-B glue, and the ZnO film/A-B glue with a patterned convex matrix was transferred onto a silicon wafer using the lift-off technology as the seed layer. Then, the hydrothermal method with different Zn(CH3COO)2 and C6H12N4 concentrations as precursors was used to synthesize ZnO nanoflower arrays on the patterned convex ZnO seed layer. XRD pattern, FESEM, FIB, and photoluminescence (PL) spectrometry were employed to observe and analyze the properties of the synthesized ZnO nanoflower arrays. When Zn(CH3COO)2 and C6H12N4 concentrations were 0.01, 0.02, 0.03, and 0.04 M, the average heights of the ZnO nanorods in the ZnO nanoflower arrays were 993, 1500, 1550, and 1650 nm, the average diameters of the ZnO nanorods were 50, 90, 105, and 225 nm, and the aspect ratios (H/D) of the ZnO nanorods were 19.9, 16.7, 14.8, and 7.33, respectively. A simple statistical and analytical method was investigated to estimate the densities (number of nanorods) of the ZnO nanoflower arrays in one 1 µm × 1 µm area. The total surface area (S) of the ZnO nanoflower arrays first increased from 5.05 × 106 and then reached a maximum value of 1.20 × 107 nm2 as Zn(CH3COO)2 and C6H12N4 concentrations increased from 0.01 to 0.02 M. For the systhesized ZnO nanoflower arrays, as the Zn(CH3COO)2 and C6H12N4 concentrations increased from 0.01 to 0.04 M, their total volume (V) increased from the 6.23 × 107 to 5.90 × 108 nm3 and the S/V ratio decreased from 8.10 × 10-2 to 1.84 × 10-2. We found that ZnO nanoflower arrays with Zn(CH3COO)2 and C6H12N4 concentrations of 0.2 M presented the maximum PL emission intensities. The calculated S/V ratios and X-ray photoelectron spectroscopy analyses are used to discuss the reasons for these results.

Effects of Composition Variations on the Crystalline Phases and Photoluminescence Properties of Ca2+x MgSi2Eu0.025O7+x Phosphors.

A solid-state reaction method was used to synthesize Ca2+x MgSi2Eu0.025O7+x (x = 0-1.0) powders in the air atmosphere and in a reduction atmosphere (95% N2 + 5% H2) at 1350 °C and 4 h, and the reduction atmosphere was removed at 800 °C. Only the Ca2MgSi2O7 phase was found in the XRD pattern of the synthesized Ca2MgSi2Eu0.025O7 powder. The first important discovery was that when the x value of Ca2+x MgSi2Eu0.025O7+x powders was increased from 0.2 to 0.8, both Ca2MgSi2O7 and Ca3MgSi2O8 phases coexisted in the synthesized Ca2+x MgSi2Eu0.025O7+x powders, and the diffraction intensity of the Ca2MgSi2O7 (Ca3MgSi2O8) phase decreased (increased) with the x value. The second important discovery was that the Ca2MgSi2Eu0.025O7 phosphor exhibited stronger photoluminescence excitation (PLE), photoluminescence (PL), and decay curve properties than the Ca2.2MgSi2Eu0.025O7.2 phosphor, and the Ca3MgSi2Eu0.025O8 phosphor exhibited stronger PLE, PL, and decay curve properties than the Ca2+x MgSi2Eu0.025O7+x phosphors for x = 0.4, 0.6, and 0.8. For x = 0.2-0.8, the PL spectra of the Ca2+x MgSi2Eu0.025O7+x phosphors were a combination of the PL spectra of Ca2MgSi2Eu0.025O7 and Ca3MgSi2Eu0.025O8 phosphors. The third important discovery was that as the x value was increased, the maximum emission peak wavelengths of the Ca2+x MgSi2Eu0.025O7+x phosphors shifted to a lower value, the maximum emission intensity of the PL spectra increased, and the emission light changed from green and cyan to blue.

A Novel Synthesis of ZnO Nanoflower Arrays Using a Lift-Off Technique with Different Thicknesses of Al Sacrificial Layers on a Patterned Sapphire Substrate.

A novel method to synthesize large-scale ZnO nanoflower arrays using a protrusion patterned ZnO seed layer was investigated. Different thicknesses of aluminum (Al) film were deposited on the concave patterned sapphire substrate as a sacrificial layer. ZnO gel was layered onto the Al film as a seed layer and OE-6370HF AB optical glue was used as the adhesive material. A lift-off technique was used to transfer the protrusion patterned ZnO/AB glue seed layer to a P-type Si <100> wafer. The hydrothermal method using Zn(CH3COO)2 and C6H12N4 solutions as liquid precursors was used to synthesize ZnO nanoflower arrays on the patterned seed layer. X-ray diffraction spectra, field-effect scanning electron microscopy, focused ion beam milling (for obtaining cross-sectional views), and photoluminescence (PL) spectrometry were used to analyze the effects that different synthesis times and different thicknesses of Al sacrificial layer had on the properties of ZnO nanoflower arrays. These effects included an increased diameter, and a decreased height, density (i.e., number of nanorods in µm-2), total surface area, total volume, and maximum emission intensity of PL spectrum. We showed that when the synthesis time and the thickness of the Al sacrificial layer were increased, the emission intensities of the ultraviolet light and visible light had different variations.

Effects of synthesis methods and different concentrations of Eu3+ ions on the emission properties of Sr2 SiO4 phosphors.

Sr2-x SiO4 -xEu (x = 0.01, 0.02, 0.035, and 0.05) phosphors were synthesized at 1000-1,300°C for 2 h in two different processes, the solid-state reaction (SSR) method and a two-step (TS) method, and these results revealed three important findings. The secondary Sr3 SiO5 phase was observed in 1,300° C-TS-synthesized Sr2-x SiO4 -xEu powder, but no raw materials or secondary phases were observed in the SSR-prepared Sr2-x SiO4 -xEu powders. The concentration quenching effect of Eu3+ ions was really observed in TS-prepared Sr2-x SiO4 -xEu phosphors, which was not observed in SSR-prepared Sr2-x SiO4 -xEu phosphors. High emission intensity of charge transition state (CT) band was observed in the photoluminescence excitation spectra, for that the 265 and 393 nm were used as the excitation wavelengths of Sr2-x SiO4 -xEu phosphors. Sr2-x SiO4 -xEu phosphors under different synthesis processes and excitation wavelengths would have different main emission peaks in the photoluminescence emission spectra. In this study, we also well discussed and explored the relationships of photoluminescence properties with the dipole transitions (electric or magnetic) of Eu3+ ions and the different coordination structures of Sr+2 ions.

Effect of different temperatures to remove reduction gas on the photoluminescence properties of Eu-doped Li2 (Ba1-x Srx )SiO4 phosphors.

In this study, Eu-doped Li2 (Ba1-x Srx )SiO4 powders (x = 0, 0.2, 0.4, and 0.6) were synthesized at 850°C in a reduction atmosphere (5% H2 + 95% N2 ) for a duration of 1 h using a solid-state reaction method. The reduction atmosphere was infused as the synthesis temperature reached 850°C, and was removed as the temperature dropped to 800-500°C. Li2 (Ba1-x Srx )SiO4 (or Li2 BaSiO4 ), (Ba,Sr)2 SiO4 (or BaSiO4 ), and Li4 SiO4 phases co-existed in the synthesized Eu-doped Li2 (Ba1-x Srx )SiO4 powders. A new finding was that the reduction atmosphere removing (RAR) temperature of the Li2 (Ba1-x Srx )SiO4 phosphors had a large effect on their photoluminescence excitation (PLE) and PL properties. Except for the 800°C-RAR-treated Li2 BaSiO4 phosphor, PLE spectra of all other Li2 (Ba1-x Srx )SiO4 phosphors had one broad emission band with two emission peaks centred at ~242 and ~283 nm; these PL spectra had one broad emission band with one emission peak centred at 502-514 nm. We showed that the 800°C-RAR-treated Li2 BaSiO4 phosphor emitted a red light and all other Li2 (Ba1-x Srx )SiO4 phosphors emitted a green light. Reasons for these results are discussed thoroughly.

Effect of V2O5 B-site substitution on the microstructure, Raman spectrum, and dielectric properties of SrBi2Ta2O9 ceramics.

Strontium bismuth tantalate vanadate [SrBi2(Ta2-xVx)O9, SBTV] ceramics, which are bismuth-layered perovskite ferroelectrics, were synthesized through the solid-state reaction method. The effects of different sintering temperatures and V2O5 contents on the structure of the microstructure, Raman spectrum, and dielectric properties of the SBTV ceramics were investigated. As sintered at high temperature (980-1040 °C) and different V2O5 contents (x = 0.1 - x = 0.4), only disk-like grains of the SBTV ceramics were observed in the scanning electron micrographs. Preferential orientation of the crystals of the SBTV ceramics was confirmed through X-ray diffraction studies. The higher dielectric constant and Curie temperature of the SBTV ceramics compared with those of strontium bismuth tantalite (SrBi2Ta2O9, SBT) ceramics are ascribe to the partial replace of Ta5+ ions by V5+ ions in the B sites. The Curie-Weiss law and the modified Curie-Weiss law were used to discuss the normal-type or relaxor-type ferroelectric characteristic of the SBTV ceramics. The Ta5+ ion replaced by V5+ ion site in SBT ceramics to form SBTV ceramics exerted a pronounced effect on the BO6 mode, as demonstrated by Raman spectrum results.

Numerical analysis of an ultra-wideband metamaterial absorber with high absorptivity from visible light to near-infrared.

In this study, we designed a novel ultra-wideband (UWB) absorber and numerically analyzed it to demonstrate that its light absorptivity was greater than 90% in the wavelength range of visible light and near-infrared (405-1505 nm). The structure of proposed novel UWB absorber consisted of four layers of films, including silica, titanium, magnesium fluoride, and aluminium, and the upper silica and titanium layers had rectangular cubes in them. For that, the excitations of propagating surface plasmon resonance (PSPR), local surface plasmon resonance (LSPR), and the resonance of Fabry-Perot (FP) cavity were generated at the same time and combined to reach the effect of perfect absorption and ultra-wideband. The proposed absorber had an average absorptivity of 95.14% in the wavelength range of 405 ∼ 1505 nm when the light was under normal incidence. In addition, the UWB absorber was large incident angle insensitive and polarization-independent. The absorber proposed in the paper had great prospects in the fields of thermal electronic equipment, solar power generation, and perfect cloaking.

Correlation among photoluminescence and the electronic and atomic structures of Sr2SiO4:xEu3+ phosphors: X-ray absorption and emission studies.

A series of Eu3+-activated strontium silicate phosphors, Sr2SiO4:xEu3+ (SSO:xEu3+, x = 1.0, 2.0 and 5.0%), were synthesized by a sol-gel method, and their crystalline structures, photoluminescence (PL) behaviors, electronic/atomic structures and bandgap properties were studied. The correlation among these characteristics was further established. X-ray powder diffraction analysis revealed the formation of mixed orthorhombic α'-SSO and monoclinic ß-SSO phases of the SSO:xEu3+ phosphors. When SSO:xEu3+ phosphors are excited under ultraviolet (UV) light (λ = 250 nm, ~ 4.96 eV), they emit yellow (~ 590 nm), orange (~ 613 nm) and red (~ 652 and 703 nm) PL bands. These PL emissions typically correspond to 4f-4f electronic transitions that involve the multiple excited 5D0 → 7FJ levels (J = 1, 2, 3 and 4) of Eu3+ activators in the host matrix. This mechanism of PL in the SSO:xEu3+ phosphors is strongly related to the local electronic/atomic structures of the Eu3+-O2- associations and the bandgap of the host lattice, as verified by Sr K-edge and Eu L3-edge X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure, O K-edge XANES and Kα X-ray emission spectroscopy. In the synthesis of SSO:xEu3+ phosphors, interstitial Eu2O3-like structures are observed in the host matrix that act as donors, providing electrons that are nonradiatively transferred from the Eu 5d and/or O 2p-Eu 4f/5d states (mostly the O 2p-Eu 5d states) to the 5D0 levels, facilitating the recombination of electrons that have transitioned from the 5D0 level to the 7FJ level in the bandgap. This mechanism is primarily responsible for the enhancement of PL emissions in the SSO:xEu3+ phosphors. This PL-related behavior indicates that SSO:xEu3+ phosphors are good light-conversion phosphor candidates for use in near-UV chips and can be very effective in UV-based light-emitting diodes.