Energy Dispersive X-ray Spectroscopy Data Research Articles

Oxygen Reaction of Nonlayered Tetrahedral KFeO2 Positive Electrode for Potassium-Ion Battery Using an FSA-based Ionic Liquid Electrolyte

K-ion batteries (KIBs) that use ionic liquid (IL) electrolytes are promising candidates for post-Li-ion batteries because of the abundance of potassium resources and safety of ILs. We successfully synthesized stoichiometric KFeO2 using a solid-state method and evaluated its charge–discharge performance as a KIB positive electrode material, with an amide-based IL electrolyte at 298 K. Transmission electron microscopy, X-ray photoelectron spectroscopy, synchrotron soft X-ray absorption spectroscopy, and energy-dispersive X-ray spectroscopy data showed that the bulk redox and surface oxidation of oxygen, rather than those of iron, contribute to the reversible and irreversible capacities, respectively. Capacity decay occurred upon repeated cycling, owing to the surface irreversible oxidation of oxygen ions to form O2 and K1−x FeO2−x/2, which blocks the pathways of K+ transfer to KFeO2 particles. This study provides a vital platform for constructing novel KIBs and elucidates the important role of oxygen in KFeO2 positive electrode.

Bifunctional bimetallic PtNi, PtCu, and NiCu nanoparticles: Electrocatalytic activities for hydrogen evolution reaction and magnetic properties

Pt-based materials are commonly used in sustainable energy technologies and fuel cells due to their catalytic ability. In this study, we synthesized bifunctional bimetallic PtNi, PtCu, and NiCu nanoparticles using the modified polyol method to investigate their catalytic for hydrogen evolution reactions (HER) and magnetic properties. X-ray diffraction and Rietveld refinement analyses revealed that all samples exhibited a face-centered cubic structure with a Fm3¯m space group. The chemical compositions of PtNi, PtCu, and NiCu bimetallic NPs were determined to be Pt28Ni72, Pt25Cu75, and Ni27Cu73, via stoichiometric calculations using the energy-dispersive X-ray spectroscopy data. The nanostructure and size were characterized by scanning electron microscopy, and the average particle size was found to be between 10 and 13 nm for all three catalysts with a narrow size distribution. The Pt28Ni72 catalyst exhibited the highest HER activity, with a minimum overpotential of −33 mV at −10 mA cm−2 and Tafel slopes with 55 mV dec-1 revealing the Volmer– Heyrovsky HER mechanism. The HER performance of the catalysts revealed that the highest HER activity is Pt28Ni72 > Pt25Cu75 > Ni27Cu73. The magnetic results revealed that the PtNi NPs exhibited a ferromagnetic to paramagnetic transition with a large coercive field of 628 Oe at 5 K. In this work, the addition of magnetic Ni in the structure resulted in multifunctional materials such as magnetically reusable bimetallic PtNi, PtCu, and NiCu catalysts with potential biomedical applications.

Optimizing curing agent ratios for high-performance thermosetting phthalonitrile-based glass fibers

Abstract Phthalonitrile (PN) is a highly promising material in the field of high-performance thermosetting polymers due to its ability to maintain its properties even at extremely high temperatures. The goal of this study was to investigate the effects of varying curing agents on the thermal properties of cured PN resin. The curing agents were found to effectively cure the resin, as indicated by the increasing ratio of N and S contents and decreasing the C content as the proportion of curing agents increased, as observed by scanning electron microscopy and energy dispersive X-ray spectroscopy data analyses. Moreover, thermogravimetric analyses revealed that the sample with 20% curing agent showed the highest thermal decomposition rate among the 2, 5, 10, and 20% curing agent dosages. These properties can be further improved by incorporating glass fibers. Overall, these results demonstrate the successful use of curing agents to create an efficient and functional polymer with superior thermal properties that are suitable for use in harsh environments. The findings of this study are a significant step forward in advancing the use of PN as a high-performance thermosetting polymer.

Molar-Fraction-Tunable Synthesis of Ag–Au Alloy Nanoparticles via a Dual Evaporation–Condensation Method as Supported Catalysts for CO Oxidation

The properties of nanoparticles composed of two metallic elements are affected by their synergy as well as the composition and structure of nanocrystals. Therefore, precise adjustment of the molar fractions of the constituent elements and crystal structure is required for their successful synthesis. An evaporation–condensation method, which represents an aerosol nanoparticle synthesis method, is based on the reagglomeration of metallic elements in the gas phase. In this study, we utilized a dual evaporation–condensation method with two furnaces to adjust the molar fractions of Ag–Au nanoparticles with an alloy-type nanocrystalline structure and obtain spherical particles with sizes smaller than 10 nm. The molar fraction of Ag atoms in the synthesized particles varied between 0 and 80% depending on the heating temperature. Energy-dispersive X-ray spectroscopy data revealed that Ag and Au elements were present in all particles and formed an alloy structure, suggesting that alloyed composite particles with different stoichiometries can be easily fabricated via the dual evaporation–condensation method. In addition, the nanoparticles generated in the gas phase were successfully recovered by immobilization on a substrate and served as effective bimetallic catalysts for CO oxidation. It is noteworthy that the preparation of nanoparticles and their fixation to a substrate in the proposed method were performed in one step.

Manufacturing of ceramic lightweight aggregates from oil-based drill cutting pyrolysis residues

ABSTRACT In this study, high-strength ceramic lightweight aggregates were prepared from oil-based drill cutting pyrolysis residues, and their formation mechanism and expansion during sintering were examined. It was found that the Al2O3 suppressed the melting process and increased the particle strength. In particular, Al atoms penetrated the liquid phase and formed a Si–Al–O crystal structure with four ligands, which reacted with CaO and BaO to produce aluminosilicate crystals, such as BaAl2Si2O8 and CaAl2Si2O8, which increased the compressive strength. Scanning electron microscope images revealed that the glass phase also contributed toward the high strength of ceramic materials by adhering to crystal grains and forming a concrete-like structure. Energy-dispersive X-ray spectroscopy data suggested that similar to Ca atoms, Ba atoms in pyrolysis residues played a critical role in the production of aluminosilicate, while transmission electron microscopy images confirmed that different phases were not well separated as Ba and Ca were stabilized in the same crystal grains. After SiC addition and increasing the sintering temperature, the product density significantly decreased while its porosity increased.

Magnetic and optical properties of ZnO/Ni/ZnO multilayer film on Si(100) and sapphire substrates

The optical absorption, band gap, and magnetic properties of ZnO/Ni(t)/ZnO multilayer film structures were investigated in various Ni layer thicknesses and substrates. We deposited 1, 4, and 5 nm of Ni film by thermal evaporation technique that sandwiched between ZnO films (~15 nm) via radio frequency magnetron sputtering method on both Si(100) and sapphire substrates. Although x-ray diffraction (XRD) analysis confirmed the (002) crystalline plane of ZnO without any Ni crystal phases on Si(100) surface, the better crystalline directions of ZnO, hexagonal wurtzite structure, was observed on the sapphire substrate. In the XRD analysis, we observed the cubic structure of NiO film formation due to thermally oxidation of Ni ions with interactions ZnO layer. Atomic force microscopy images confirmed the effect of the Ni layer on the average island size of 23.9 ± 2.9 nm and 25.6 ± 6.2 of ZnO films on 4 and 5 nm Ni films, respectively. Energy dispersive x-ray spectroscopy data confirmed that there is no other atom or impurity in the sample structure. The optical transparency of the multilayer films was reduced with increasing Ni layer thickness and maximum transparency was obtained as 97% at 800 nm of wavelength for the film with 1 nm Ni. The direct optical band gap of ZnO/Ni(t)/ZnO films was found to be 3.25, 3.20, and 3.12 eV with the contribution of 1, 4, and 5 nm Ni film in the multilayer film stack. The maximum Hc is found to be 1000 Oe for Si substrates and this value is reduced to around 400 Oe due to the crystal formation of the NiO layer for sapphire substrate samples.

Benchtop Electrochemical Growth and Controlled Alloying of Polycrystalline InxGa1–xAs Thin Films

Compared to Si, GaAs offers unique material advantages such as high carrier mobility and energy conversion efficiency, making GaAs a leading competitor to replace Si on several technological fronts related to optoelectronics and solar energy conversion. Alloying the GaAs lattice with elemental In allows the direct bandgap of the resulting ternary alloy to be tuned across the near-infrared (NIR) region of the electromagnetic spectrum from ∼0.9 to 3.5 μm. However, methods of fabricating high-quality crystalline GaAs are currently limited by their high cost and low throughput relative to Si growth methods, suggesting the need for alternative low-cost routes to GaAs growth and alloying. This research documents the first instance in the literature of the electrodeposition and controlled alloying of polycrystalline InxGa1–xAs films at ambient pressure and near-room temperature using the electrochemical liquid–liquid–solid (ec-LLS) process. X-ray diffraction and Raman spectroscopy support the polycrystalline growth of (111)-oriented InxGa1–xAs films. Consistent redshifts of the GaAs-like TO peaks were observed in the Raman data as the In composition of the liquid metal electrode was increased. Optical bandgaps, determined via diffuse reflectance measurements, displayed a consistent decrease with the increase in the In composition of InxGa1–xAs films. While Raman, diffuse reflectance, and energy-dispersive X-ray spectroscopy data support controlled alloying efforts, all techniques suggest an overall decrease of the In/Ga ratios present in deposited films relative to those of the liquid metal electrodes. These results lend support for the continued development of ec-LLS as a viable method of achieving crystalline growth and alloying of binary and ternary semiconductor material systems using a benchtop setup under ambient pressure and near-room temperature.

Graph-based deep learning segmentation of EDS spectral images for automated mineral phase analysis

We introduce a novel method for graph-based segmentation of spectral images obtained using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray spectroscopy (EDS) detector. The method exploits deep learning along with fusion of rasterized electron microscopy images with sparse EDS samples to obtain accurate mineralogy segmentation with high efficiency. Improvements over previous methods are with respect to the goal of an improved quantitative and qualitative assessment of segmentation, so that volumetric composition is indirectly addressed. We describe the principles of the novel method, show experimental results on real samples and demonstrate its advantages in comparison to the state of the art. The new method performs unsupervised clustering on sparsely measured EDS spectra, allowing for classification of unseen mineralogical compounds. Then, the processed spectra are combined with single channel SEM measurements through an optimized lattice, where a Markov Field is used to perform spatial segmentation in image. The benefit of this material-agnostic method is that clusters can then be (separately) classified, analyzed, and small grains with distinct EDS measurements are more accurately separated than in previous methods. These improved results are evaluated quantitatively on ground-truth electron microscope measurements with dense high-count EDS data, as well as visually through analysis by a mineralogist.

Role of Zeolite Structural Properties toward Iodine Capture: A Head-to-head Evaluation of Framework Type and Chemical Composition

This study evaluated zeolite-based sorbents for iodine gas [I2(g)] capture. Based on the framework structures and porosities, five zeolites, including two faujasite (FAU), one ZSM-5 (MFI), one mesoMFI, one ZSM-22 (TON), as well as two mesoporous materials, were evaluated for I2(g) capture at room temperature and 150 °C in an iodine-saturated environment. From these preliminary studies, the three best-performing zeolites were ion-exchanged with Ag+ and evaluated for I2(g) capture under similar conditions. Energy-dispersive X-ray spectroscopy data suggest that Ag-FAU frameworks were the materials with the highest capacity for I2(g) in this study, showing ∼3× higher adsorption compared to Ag-mordenite (Ag-MOR) at room temperature, but X-ray diffraction measurements show that the faujasite structure collapsed during the adsorption studies because of dealumination. The Ag-MFI zeolites are decent sorbents in real-life applications, showing both good sorption capacities and higher stability. In-depth analyses and characterizations, including synchrotron X-ray absorption spectroscopy, revealed the influence of structural and chemical properties of zeolites on the performance for iodine adsorption from the gas phase.

Green synthesis of MnxZn(1−x)O nanostructure using Azadirachta indica leaf extract and its microstructural and optical study

Zinc Oxide (ZnO) nanostructures doped with manganese (Mn: 5% and 10%) were prepared by the green synthesis method using the leaf extracts of Azadirachta indica. The microstructural investigation of the prepared nanopowders was carried out with the Rietveld refinement of the x-ray diffraction data. The phase analysis of the x-ray diffraction data confirmed that the synthesized nanoparticles have the hexagonal wurtzite structure in all cases. The Williamson Hall method was used to analyze the data obtained after the Rietveld refinement analysis to find some important microstructural parameters such as crystallite size, strain, stress, and energy density. The size of the crystallites is almost the same in both cases and the values for strain, stress, and energy density increase with increasing Mn concentration. Functional groups and molecular interactions were identified by the Fourier Transform Infra-Red spectroscopy spectra. UV-visible spectra show that the bandgap energy decreases with increasing Mn content. This property can help to fabricate a photodetector that can operate at a wavelength longer than the cut-off wavelength of ZnO. The morphology of the synthesized nanostructure was studied by field emission scanning electron microscope. The energy dispersive x-ray spectroscopy data confirm the elemental compositions in the synthesized Mn-doped ZnO, which means that the desired nanostructures were successfully synthesized by the green method.

Air pore structure, strength and frost resistance of air-entrained mortar with different dosage of nano-SiO2 hydrosol

The use of nano-SiO2 in concrete has attracted intense attention recently due to its notable improvement in mechanical properties as well as consumption of industrial by-product to enhance the life cycle sustainability. However, the effect of nano-SiO2 on the air pore structure and properties of air entrained cement-based materials is almost not involved in former studies. In this paper, the influence of nano-SiO2 hydrosol (NSH) on the air pore structure, strength and frost resistance of air-entrained mortar was reported. Two typical air entrained agents (AEAs) were utilized to prepare air-entrained mortar with the targeted air content of fresh mortar at the same level. The effects of the addition of NSH on air pore structure, hydration heat release and frost resistance of air-entrained mortar were investigated. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) were used to analyze the mechanism of NSH on entrained air bubbles and pores. Results suggest that the incorporation of NSH can affect entrained air bubble behavior, influence the pore size distribution and densify the hydration products of the air pore wall, thereby effecting the mechanical properties and frost resistance of air-entrained mortar. SEM and EDS data proved differences in chemical composition of air bubble shell entrained by two types of AEAs. The differences resulted in diverse degree of NSH affected air-entrained mortar performance. Due to the effect of early accelerated heat release of cement on the stability bubbles and excessive mortar consistency on the retention of coarse air bubble, it is not recommended to add too much NSH in order to optimize the air pore structure and frost resistance of air-entrained mortar. This study deepens our understanding into the fundamental mechanism of NSH in air-entrained mortar, which also prompts its application to create a sustainable built environment.

Mechanism of nano-silica to enhance the robustness and durability of concrete in low air pressure for sustainable civil infrastructures

Cement concrete is an extensively used construction material in buildings and civil infrastructures. As infrastructure moves into plateau areas, freeze-thaw failure is a main durability challenge for concrete due to the frequent freeze-thaw cycles and entrained air pore coarsening in high altitude and low air pressure (Lap). Recently, there has been a growing interest in the application of nano-silica (NS) due to its notable improvement in concrete durability in plateau areas as well as the consumption of industrial by-product, both improve the sustainability of civil infrastructures. Therefore, this paper studies the mechanism of NS for enhancing the robustness and durability of concrete in low air pressure, the results of which foster the application of NS concrete for designing and constructing sustainable civil infrastructures in plateau areas. Two different kinds of air-entraining agents (AEAs) were utilized to prepare air-entrained concrete. Following this, NS was employed to modify the micro and meso structure of the concrete, and then determine their influence on the performance of concrete. The influence of NS on the entrained air bubbles and air pores were analyzed via micro measurements including Fourier Transform infrared spectroscopy (FTIR), Energy-Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscope (SEM). CABR-457 hardened concrete air pore structure analyzer was employed to study microstructure of air-entrained concrete with and without NS. The results demonstrate that the adsorption of NS at air bubble shell entrained by AEAs can densify the hydration products of the air pore wall and influence the pore size distribution, thereby improving the flexural strength and frost resistance of air-entrained concrete under low air pressure. The average air pore diameter of concrete with proper AEAs can be refined by 43.3% after adding NS. SEM, EDS and FTIR data analysis proves the adsorption of NS on the air bubble shell and differences in chemical composition of air bubble shell entrained by two types of AEAs. The differences in the composition of bubble shells result in diverse degree of NS optimized concrete performance. This study deepens our understanding into the fundamental mechanism of NS in concrete in Lap, which also prompts its application to create a sustainable built environment.

Laser annealing of epitaxial CaF2 films on Si

Nanosecond time-resolved reflectivity and transmission changes in CaF2/Si(111) structures were measured to study the phase transitions, surface modification and radiolysis induced by nanosecond ruby laser pulses. The Si lattice heating up to the melting point leads to the nanohills formation on the surface of the structure, the height of which does not exceed 100 nm with the average base diameter of 360 nm and the surface density of 2•108cm– 2. The Raman scattering and energy-dispersive X-ray spectroscopy data indicate that the nanohills contain cavities inside them, and they are filled with the gas of Si2F6 molecules. The shell of the nanohills, obviously, consists of calcium oxide.

Electrochemical behaviors and electrodeposited materials of lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) on terpyridine-functionalized Ti sheets

Electrochemical recovery of lanthanide metals has been a very important process for the treatments of nuclear and electronic wastes. In the present study, we established a big data set of lanthanide (III) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions on electrochemical behaviors and electrodeposition over bare and terpyridine-functionalized Ti sheets. Cyclic voltammetry and amperometry experiments were performed in a 0.1 M NaClO4 supporting electrolyte. The electrodeposited films were fully examined by scanning electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy, and photoluminescence. FT-IR and EDXS data confirmed that all the electrodeposited lanthanide materials were of a similar lanthanide complex. Photoluminescence imaging profiles were also obtained for selected Eu(III)-deposited films. The newly established data set could be very useful for understanding electrochemical behaviors of lanthanide ions, improvement of recovery method, and fabrication of catalyst electrode materials by electrodeposition.

Layer spacing gradient (NaLi)1−xCoO2 for electrochemical Li extraction

Layer spacing gradient (NaLi)1−xCoO2 for electrochemical Li extraction

Phytoassisted synthesis of magnesium oxide nanoparticles from Pterocarpus marsupium rox.b heartwood extract and its biomedical applications

BackgroundUnlike chemical techniques, the combination of metal oxide nanoparticles utilizing plant concentrate is a promising choice. The purpose of this work was to synthesize magnesium oxide nanoparticles (MgO-NPs) utilizing heartwood aqueous extract of Pterocarpus marsupium. The heartwood extract of Pterocarpus marsupium is rich in polyphenolic compounds and flavonoids that can be used as a green source for large-scale, simple, and eco-friendly production of MgO-NPs. The phytoassisted synthesis of MgO is characterized by UV-Visible spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) with EDS (energy dispersive X-ray spectroscopy), and transmission electron microscopy (TEM). ResultsThe formation of MgO-NPs is confirmed by a visual color change from colorless to dark brown and they displayed a wavelength of 310 nm in UV-Spectrophotometry analysis. The crystalline nature of the obtained biosynthesized nanoparticles are revealed by X-ray diffraction analysis. SEM results revealed the synthesized magnesium oxide nanoparticles formed by this cost-effective method are spherically shaped with an average size of < 20 nm. The presence of magnesium and oxygen were confirmed by the EDS data. TEM analysis proved the spherical shape of the nanoparticles with average particle size of 13.28 nm and SAED analysis confirms the crystalline nature of MgO-NPs. FT-IR investigation confirms the existence of the active compounds required to stabilize the magnesium oxide nanoparticles with hydroxyl and carboxyl and phenolic groups that act as reducing, stabilizing, and capping agent. All the nanoparticles vary in particle sizes between 15 and 25 nm and obtained a polydispersity index value of 0.248. The zeta-potential was measured and found to be − 2.9 mV. Further, MgO-NPs were tested for antibacterial action against Staphylococcus aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria) by minimum inhibitory concentration technique were found to be potent against both the bacteria. The blended nanoparticles showed good antioxidant activity examined by the DPPH radical scavenging method, showed good anti-diabetic activity determined by alpha-amylase inhibitory activity, and displayed strong anti-inflammatory activity evaluated by the albumin denaturation method. ConclusionsThe investigation reports the eco-friendly, cost-effective method for synthesizing magnesium oxide nanoparticles from Pterocarpus marsupium Rox.b heartwood extract with biomedical applications. Graphical abstract▪

The effect of the polishing procedure and surface sealant application on the fluoride release of different restorative materials

Aim: The aim of this study is to evaluate the effect of the polishing procedure and surface sealant application on the fluoride release of different restorative materials. Materials and Methods: The study groups composed of five different restorative materials: Beautifil II, GCP Glass Fill, Amalgomer CR, Zirconomer, and Fuji IX GP. 30 disk-shaped specimens (8 mm diameter × 2 mm thickness) were prepared from each material. Each group was divided into three subgroups according to the finishing procedure: Mylar strip, polishing with Super-Snap discs, polishing with Super-Snap discs followed by G-Coat Plus application. The amount of fluoride released was measured using a fluoride ion-selective electrode and ion analyzer after 24 h followed by measurement on days 3, 7, 15, 21, and 28. Surface analysis of the materials was performed with scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS). The data were statistically analyzed using repeated measure analysis of variance and the least significant difference test (P = 0.05). Results: The highest amounts of fluoride release were found during the first 24 h for all materials. The amounts of fluoride release revealed a significant decrease from day 1 to day 28 for each group (P 0.05). According to EDS data, the most percentage of oxygen was found in all materials. Conclusions: It might be concluded that polishing promoted a significant increase of fluoride release on glass ionomer-based materials, and the fluoride release of the restorative materials was not affected by applying G-Coat Plus.

Effect of nano-SiO2 hydrosol on size distribution, coalescence and collapse of entrained air bubbles in fresh cement mortar

In the fresh state of cement-based composite materials, entrained air bubbles change dynamically due to the continuous coalesce and collapse caused by physical and chemical factors. These processes affect the pore structure formed in the later stage. However, only few studies emphasized the process of bubble size refinement and pore evolution. In this paper, attempts have been made to optimize the size distribution of entrained air bubble and prevent the coalescence of fine entrained air bubbles in the fresh air-entraining cement mortar contained nano-SiO2 hydrosol (NSH). Two different kinds of commercial air entraining agents (AEAs) were utilized. The fluidity and initial air content of each mortar set were controlled during the test to prevent the influence on the behavior of entrained bubbles. An Air Void Analyzer (AVA) was used to determine the air size distribution of mortar. The change of fine bubble distribution within 60 min was analyzed to evaluate the degree of coalescence of fine bubbles. By involving a novel method to prepare bubble shell samples, the mechanism of the influence of NSH on the size distribution and trends of entrained air bubble over time was analyzed via micro measurements including X-Ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscope (SEM). Results suggest that the proportion of fine bubbles less than 300 μm in mortar prepared with non-ionic air entraining agent increases with adding NSH, which effectively fined the size distribution of bubbles, while the trend of mortar prepared with anionic air entraining agent is not obvious. The coalescence degree of fine bubbles is effectively inhibited by adding nano-SiO2 into air-entraining mortar, and the inhibition effect decreases with the increase of the content of nano-SiO2. XRD, EDS, and SEM data analysis proved the adsorption of nano-SiO2 on the bubble shell entrained by AEAs. The composition of air bubble shell has a great influence on the adsorption and effect of nano-SiO2. Nano-SiO2 adsorbed on the surface of bubble shell can enhancing mechanical strength of bubble shell and accelerating the hydration of tricalcium silicate at the same time, thus affecting the behavior of the bubble. At last, the method of optimizing air bubble distribution by incorporating nano-SiO2 is suggested for air-entraining cement-based composites mixed with non-ionic air entraining agent.

Transparent and conductive CdS:Ca thin films for optoelectronic applications

This paper presents the structural, morphological, optical and electrical evolution of Ca-doped CdS thin films. Non-doped and Ca-doped CdS samples with various amounts of Ca atoms (from 0 to 10 at.% with an increasing step of 2 at.%) were grown by spray pyrolysis route on glass slides. The structural investigation by X-ray diffraction showed that Ca-doping distorted CdS structure until 8 at.% Ca-doping and then a slight improvement in the intensity of (101) peak was obtained for 10 at.% Ca-doping compared to the other Ca-doping samples. Morphological analysis displayed a grain growth for a low amount of Ca-doping whereas higher concentration of Ca-doping led to a reduction in the grain size of CdS thin films. More stoichiometric CdS specimens were obtained after various amounts of Ca-doping according to energy dispersive X-ray spectroscopy data. Transparency of the CdS samples enhanced remarkably with the incorporation of Ca atoms in CdS with a particular concentration of 10 at.%. Tauc’s plot investigation illustrated that the bandgap score of samples changed from 2.54 eV for non-doped CdS to 2.48 eV for 4 at.% Ca-doped CdS thin films. Further increase of Ca-doping doesn’t vary the bandwidth of CdS samples. Photoluminescence data indicated that Ca-doped CdS thin films had lower intrinsic defects compared with non-doped CdS one. The electrical examination demonstrated that the carrier density of CdS thin films increased till 6 at.% Ca-doping and then decreased further increase of Ca-doping. However, resistivity values exhibited the opposite behavior accordingly. In conclusion, it can be pronounced that 6 at.% Ca-doped CdS thin films are the optimum specimen to be used as an effective transparent and conductive material in the optoelectronic devices.

Kinetically Limited Phase Formation of Pt-Ir Based Compositionally Complex Thin Films.

The phase formation of PtIrCuAuX (X = Ag, Pd) compositionally complex thin films is investigated to critically appraise the criteria employed to predict the formation of high entropy alloys. The formation of a single-phase high entropy alloy is predicted if the following requirements are fulfilled: 12 J∙K−1 mol−1 ≤ configurational entropy ≤ 17.5 J∙K−1 mol−1, −10 kJ∙mol−1 ≤ enthalpy of mixing ≤ 5 kJ∙mol−1 and atomic size difference ≤ 5%. Equiatomic PtIrCuAuX (X = Ag, Pd) fulfill all of these requirements. Based on X-ray diffraction and energy-dispersive X-ray spectroscopy data, near-equiatomic Pt22Ir23Cu18Au18Pd19 thin films form a single-phase solid solution while near-equiatomic Pt22Ir23Cu20Au17Ag18 thin films exhibit the formation of two phases. The latter observation is clearly in conflict with the design rules for high entropy alloys. However, the observed phase formation can be rationalized by considering bond strengths and differences in activation energy barriers for surface diffusion. Integrated crystal orbital Hamilton population values per bond imply a decrease in bond strength for all the interactions when Pd is substituted by Ag in PtIrCuAuX which lowers the surface diffusion activation energy barrier by 35% on average for each constituent. This enables the surface diffusion-mediated formation of two phases, one rich in Au and Ag and a second phase enriched in Pt and Cu. Hence, phase formation in these systems appears to be governed by the complex interplay between energetics and kinetic limitations rather than by configurational entropy.