First-Principles Insights into Structural, Optoelectronic, and Elastic Properties of Fluoro-Perovskites KXF3 (X = Ru, Os).

The need for new and better semiconductor materials for use in renewable energy devices motivates us to study KRuF3 and KOsF3 fluoride materials. In the present work, we computationally studied these materials and elaborate their varied properties comprehensively with the assistance of density functional theory-based techniques. To find the structural stability of these under-consideration materials, we employed the Birch-Murnaghan fit, while their electronic characteristics were determined with the usage of modified potential of Becke-Johnson. During the study, it became evident from the band-structure results of the KRuF3 and KOsF3 materials that both present an indirect semiconductor nature having the band gap values of 2.1 and 1.7 eV, respectively. For both the studied materials, the three essential elastic constants were determined first, which were further used to evaluate all the mechanical parameters of the studied materials. From the calculated values of Pugh's ratio and Poisson's ratio for the KRuF3 and KOsF3 materials, both were verified to procure the nature of ductility. During the study, we concluded from the results of absorption coefficient and optical conduction in the UV energy range that both the studied materials proved their ability for utilization in the numerous future optoelectronic devices.

Influence of Zirconium (Zr4+) Substitution on the Crystal Structure and Optical and Dielectric Properties of Sr0.8Mg0.2(Sn1-xZrx)O3 Ceramics.

In this work, new compositions of Sr0.8Mg0.2(Sn1-xZrx)O3 0.00 ≤ x ≤ 0.06 ceramics are designed and synthesized by the conventional solid-state route. The influence of Zr doping on the phase, microstructural, optical, and dielectric properties is thoroughly investigated. The peaks (0 0 4) and (1 1 0) are observed to shift toward lower 2θ values, due to the variation of the ionic radius between Zr4+ and Sn4+. X-ray diffraction patterns reveal the orthorhombic structure with the space group Pbnm. Scanning electron microscopy images reveal the presence of pores and particles with a high degree of agglomeration. The functional groups and modes of vibration are determined by Fourier transform infrared spectroscopy of the prepared metal oxide samples. The existence of green emission of all the synthesized samples around 554.91 nm is identified by photoluminescence spectroscopy. The dielectric properties of the fabricated samples are measured by using an impedance analyzer. The values of the tangent loss and relative permittivity are found to decrease with increasing frequency.

Impact of Cobalt Doping on the Structural, Optical, and Dielectric Properties of MgAl2O4 Spinel Material.

Nanomaterials (NMs) with structural, optical, and dielectric properties are called functional or smart materials and have favorable applications in various fields of material science and nanotechnology. Pure and Co-doped MgAl2O4 were synthesized by using the sol-gel combustion method. A systematic investigation was carried out to understand the effects of the Co concentration on the crystalline phase, morphology, and optical and dielectric properties of Co-doped MgAl2O4. X-ray diffraction confirmed the cubic spinel structure with the Fd3̅m space group, and there was no impurity phase, while the surface morphology of the samples was investigated by scanning electron microscopy. The dielectric properties of the synthesized material are investigated using an LCR meter with respect to the variation in frequency (1-2 GHz), and their elemental composition has been examined through the energy-dispersive X-ray technique. The existence of the metal-oxygen Mg-Al-O bond has been confirmed by Fourier transform infrared spectroscopy. The value of the dielectric constant decreases with the increasing frequency and Co concentration. The optical behaviors of the Co2+-doped MgAl2O4 reveal that the optical properties were enhanced by increasing the cobalt concentration, which ultimately led to a narrower band gap, which make them exquisite and suitable for energy storage applications, especially for super capacitors. This work aims to focus on the effect of cobalt ions in different concentrations on structural, optical, and dielectric properties.

Room-Temperature Ferromagnetism in Mn-Doped ZnO Nanoparticles Synthesized by the Sol-Gel Method.

In the current work, pure ZnO and Mn-doped ZnO nanoparticles were synthesized by the sol-gel autocombustion method. Structural analysis and phase determination were done by X-ray diffraction, and a hexagonal wurtzite structure was exhibited with disparate microstructures for all samples. Mn2+ ions were well composed, as evidenced by the fluctuation of lattice parameters, dislocation density, and lattice strain. Crystallite size decreases from 38.42 to 27.54 nm by increasing the doping concentration. Field emission scanning electron microscopy results shows the combination of evenly distributed spherical-like and hexagon-like structures. Fourier transform infrared spectra revealed that when Mn content increased, the absorption bands red-shifted. The drop in the energy band gap from 3.25 eV for ZnO to 2.99 eV for Zn0.96Mn0.04O was predicted by ultraviolet-visible absorption spectra. This red shift in the energy band gap can be explained by the sp-d exchange interaction between the band electrons of ZnO and localized d electrons of Mn. A study of magnetic properties revealed the change of the diamagnetic attribute for pure ZnO to the room-temperature ferromagnetic attribute of doped samples. In the current study, room-temperature ferromagnetism was achieved for Mn-doped ZnO nanoparticles, which can serve as a desirable option for practical applications in the future.

Impedance Study of Temperature-Stable Relaxor Dielectrics in the System of BCT-BMT Ceramics.

Preparation of a lead-free system (Ba0.8Ca0.2)TiO3-xBi(Mg0.5Ti0.5)O3 (BCT-BMT) with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was carried out using a solid-state reaction technique. X-ray (XRD) diffraction analysis confirmed a tetragonal structure for x = 0, which shifted to cubic (pseudocubic) at x ≥ 0.1. From Rietveld refinement, a single phase with a tetragonal symmetry model (P4mm) was observed for x = 0, and however, for sample x = 0.1 and sample x = 0.5, the data are modeled to cubic (Pm3m). Composition x = 0 showed a prominent Curie peak, typical of ordinary ferroelectrics with a Curie temperature (Tc) ∼130 °C, modified to a typical relaxor dielectric at x ≥ 0.1. However, samples at x = 0.2-0.5 displayed a single semicircle attributed to the bulk response of the material, whereas a slightly depressed second arc appeared for x = 0.5 at 600 °C, indicating a slight contribution to the electrical properties, ascribed to the grain boundary of the material. Finally, the dc resistivity increased with the increase of the BMT content and the solid solution increased the activation energy from 0.58 eV at x = 0 to 0.99 eV for x = 0.5. Adding the BMT content eliminated the ferroelectric behavior at compositions x ≥ 0.1 and led to a linear dielectric response and electrostrictive behavior with a maximum strain of 0.12% for x = 0.2.

First-principle insight into the structural, electronic, elastic and optical properties of Cs-based double perovskites Cs2XCrCl6 (X = K, Na).

This study communicates the theoretical investigations on the cubic double perovskite compounds Cs2XCrCl6 (X = K or Na). Density functional theory (DFT) calculations were carried out using the TB-mBJ approximation. These compounds were found to be stable in the cubic perovskite structure having lattice constants in the range of 10.58-10.20. The stability of the investigated materials was assessed by the Gold-Schmidt tolerance method, which resulted in the tolerance factor values of 0.891 and 0.951 for Cs2KCrCl6 and Cs2NaCrCl6, respectively. The calculated values of the elastic constants C11, C12, and C44 of the cubic compounds studied by our research team confirm the elastic stability. The values of the formation energies were also calculated for both the compounds and were found in the range from -2.1 to -2.3. The electronic behavior of the presently investigated materials was examined by inspecting their band structures and the density of states. It was observed that both the materials have half-metallic nature. To check the suitability of the studied compounds in optical applications, we determined the real and imaginary parts of their respective dielectric functions, absorption coefficients, optical conductivities, refractive index, and reflectivity as a function of a wide range of incident photon energies up to 40 eV.

Detail computational study about the structural, electronic, optical, and mechanical properties of RbVX3 (Cl, Br, I) halide perovskite materials.

The non-toxic nature of lead-free materials with cubic perovskite structure has attracted the researcher's attention, and huge work is ongoing for the search of such materials. Furthermore, due to demand for their utilization in diverse applications, such as photovoltaic and optoelectronics, these inorganic-halide materials have become more enchanting for engineers. In the present work, all the key properties, including structural, electronic, optical, and mechanical, of rubidium based RbVX3 (where X is chlorine, bromine, and iodine) materials were extensively studied via first-principle density functional theory (DFT). The study reveals the half-metallic nature of the currently studied materials. For the mechanical stability of RbVX3 compounds, all three independent elastic coefficients (Cij) were determined, from which it was concluded that these materials are mechanically stable. Moreover, from the Poison and Pugh's ratios, it was found that the RbVCl3 and RbVBr3 materials have ductile nature, while RbVI3 has brittle nature upon the applied stress.

Effect of Cr-Doping on the Structural and Magnetic Properties of Mechanically Alloyed FeCoNiAlMn1-xCrx High-Entropy Alloy Powder.

In this work, the new compositions of FeCoNiAlMn1-xCrx, (0.0 ≤ x ≤ 1.0), a high-entropy alloy powder (HEAP), are prepared by mechanical alloying (MA). The influence of Cr doping on the phase structure, microstructure, and magnetic properties is thoroughly investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry. It is found that this alloy has formed a simple body-centered cubic structure with a minute face-centered cubic structure for Mn to Cr replacement with heat treatment. The lattice parameter, average crystallite size, and grain size decrease by replacing Cr with Mn. The SEM analysis of FeCoNiAlMn showed no grain boundary formation, depicting a single-phase microstructure after MA, similar to XRD. The saturation magnetization first increases (68 emu/g) up to x = 0.6 and then decreases with complete substitution of Cr. Magnetic properties are related to crystallite size. FeCoNiAlMn0.4Cr0.6 HEAP has shown optimum results with better saturation magnetization and coercivity as a soft magnet.

Optimizing Structural, Optical, Dielectric, and Magnetic Properties of (Bi1-x La x )FeO3 (0.00 ≤ x ≤ 0.06) Sintered Ceramics.

(Bi1-x La x )FeO3 (0.00 ≤ x ≤ 0.06) ceramics have been synthesized through a mixed oxide route to investigate their structural, morphological, optical, dielectric, and magnetic properties. All the samples are revealed to be in rhombohedral structures along with the R3c space group and 161 space group number. A high relative permittivity and the lowest tangent loss are observed in BLFO samples at the frequency range 1-100 MHz. The optical studies show that the excitation energy increases with the increasing La content. Moreover, the magnetization being strongly affected by crystallite size and microstrain has been investigated. The band gap energy increases with the increasing La content. The overall result of pure and doped La contents in BFO ceramics shows enhanced structural, dielectric, and optical properties.

Investigation of Dielectric, Ferroelectric, and Strain Responses of (1 - x)[0.90(Bi0.5Na0.5)TiO3 - 0.10SrTiO3] - xCuO Ceramics.

The low-temperature sintering of (Bi0.5Na0.5)TiO3-based ceramics can be achieved by sintering aid CuO. Piezoelectric ceramics (1 - x)[0.90(Bi0.5Na0.5)TiO3 - 0.10SrTiO3] - xCuO (BNT-ST-Cu) with x = 0, 0.01, 0.02, 0.03, and 0.04 were prepared through the mixed oxide route. A tetragonal structure was indexed for the undoped sample. Its structure was found to be changed to a pseudocubic when Cu was added. For undoped Cu samples, the sintering temperature (T s) for sufficient densification was 1160 °C. However, T s was reduced to 1090-1120 °C for Cu-added specimens. Field emission scanning electron microscopy (FE-SEM) showed a uniform and dense grain morphology for all samples. The maximum dielectric constant temperature (T m) was decreased with the doping concentration of Cu and applied frequency. The strain was increased with Cu concentration and had the maximum value of 500 pm/V for the sample x = 0.02 with symmetric and slim strain loops.

Investigation of structural, opto-electronic and thermoelectric properties of titanium based chloro-perovskites XTiCl3 (X = Rb, Cs): a first-principles calculations.

Perovskites are a significant class of materials with diverse uses in modern technology. The structural, electronic, elastic, thermoelectric, and optical properties of RbTiCl3 and CsTiCl3 perovskites were estimated using the FP-LAPW method within the framework of density functional theory. The exchange-correlation energy of both analyzed systems was calculated using the Generalized Gradient Approximation (GGA) functional. The structures are optimized and lattice constants of 5.08 Å and 5.13 Å are found for XTiCl3 (X = Rb, Cs), respectively. The structural analysis reveals that they have cubic symmetry. Their half metallic nature was proved by their metallic nature in one spin channel and semiconducting nature in the opposing spin channel. Densities of states are calculated to predict the interaction of orbitals of distinct atoms in the compounds. From the results of optical response, it is found that these compounds show high optical absorption in the visible region of light. Moreover, thermoelectric properties of the studied materials are calculated as a function of chemical potential at different temperatures using the theory of semi-classical Boltzmann transport within BoltzTrap code. The thermoelectric response shows that the investigated compounds as p-type can be beneficial in overcoming the global warming issue.

Enhancement of the Optical and Dielectric Properties at Low Frequency of (Sr1-xCax)5Ti4O13, (0 ≤ x ≤ 0.06) Structure Ceramics.

Low loss Ruddlesden-Popper (RP) series, i.e., (Sr1-xCax)5Ti4O13, 0.0 ≤ x ≤ 0.06, has been synthesized by a mixed oxide route. In this work, the substitution of Ca2+ cation in Sr5Ti4O13 sintered ceramics was chosen to enhance the structural, optical, and dielectric properties of the product. It was found that the Ca2+ content has significant effects on enhancing the dielectric properties as compared to Mn and glass additions. It was observed that the relative density, band gap energy, and dielectric loss (tangent loss) increase while relative permittivity decreases along with Ca2+ content. High relative density (96.7%), low porosity, and high band gap energy (2.241 eV) values were obtained in (Sr1-xCax)5Ti4O13, 0.0 ≤ x ≤ 0.06 sintered ceramics. These results will play a key role in the application of dielectric resonators.

Structural, electronic, magnetic and elastic properties of xenon-based fluoroperovskites XeMF3 (M = Ti, V, Zr, Nb) via DFT studies.

In this work, the structural, electronic, magnetic and elastic properties of the xenon-based fluoroperovskites XeMF3 (M = Ti, V, Zr, Nb) have been studied using density functional theory. The structural study reveals that all the perovskites have stable structures. A half-metallic nature is observed due to the presence of a band gap in only the spin-down channel. The result indicates that the considered compounds are ferromagnetic materials with integer magnetic moments. The elastic parameters were studied to obtain their elastic properties. It is noted that all compounds have an anisotropic nature and show ductility. The optical characteristics show that these compounds are good optical absorbers at high energy. Furthermore, we suggest that these compounds could be good candidates for spintronic and optoelectronic devices.

Study of the Role of Titanium and Iron Cathodic Cages on Plasma-Nitrided AISI 430 Ferritic Stainless Steel.

In contrast to austenitic and martensitic stainless steels, ferritic stainless steels have a lower hardness and wear resistance but exhibit excellent corrosion resistance. Due to this fact, their use in the aerospace, automobile, and house construction industries is restricted. Several methods have been utilized to enhance the tribological characteristics of ferritic stainless steels. In this work, titanium nitride coating has been carried out by using a cathodic cage of titanium material, and later on, the titanium cathodic cage is replaced by an AISI-304 cathodic cage in a CCPN chamber to form iron nitride coating on AISI-430 ferritic stainless steel coupons through a plasma nitriding process for 4 h at a fixed temperature of 400 °C. The microstructures and mechanical traits of all processed and control coupons were analyzed using scanning electron microscopy, X-ray diffraction, ball-on-disc wear tester, and microhardness tester techniques. The results showed that hardness increased up to 1489 HV with the titanium cage, which is much higher than the hardness of the base material (270 HV). The titanium cage-treated coupons have high layer thickness, smooth surface morphology, and a minimum crystallite size of 2.2 nm. The wear rate was reduced up to 50% over the base material after the titanium cage plasma treatment. The base coupon exhibited severe abrasive wear, whereas nitrided coupons exhibited dominant adhesive wear. In the iron nitride coatings, this effect is also important, owing to the more influential cleaning process in a glow discharge, and the better adhesion with enhanced interlayer thickness is attributed to the fact that the compliance of the interlayer minimizes shear stresses at the coating-substrate interface. The use of a graded interface improves adhesion compared with the case where no interlayer is used but a titanium interlayer of comparable thickness provides a significant increase in measured adhesion. For both titanium and iron nitride films, there is a reduction in wear volume which is a function of interlayer thickness; this will have a substantial effect on wear lifetime. Thus by careful control of the interlayer thickness and composition, it should be possible to improve coating performance in tribological applications.

Room-Temperature Ferromagnetism in Cu/Co Co-Doped ZnO Nanoparticles Prepared by the Co-Precipitation Method: For Spintronics Applications.

In current work, pure ZnO and Zn0.96-x Cu0.04Co x O (0 ≤ x ≤ 0.05) nanoparticles were synthesized by the co-precipitation method. Structural analysis and phase determination of the formed nanoparticles was carried out using X-ray diffraction (XRD) and Williamson-Hall plots. The hexagonal wurtzite structure was manifested by all the samples with divergent microstructures. The change in lattice parameters, bond length, dislocation density, and lattice strain indicates that Cu and Co were successfully incorporated. Average crystallite size was found to be in the range of 32.16-45.42 nm for various doping concentrations. Field emission scanning electron microscopy results exhibited that the surface morphology is an amalgam of spherical-like and hexagon-like structures. Spherical-shaped grains were homogeneous and evenly distributed all over the structure. Fourier transform infrared spectra indicated that the absorption bands were blue-shifted with increasing Co concentration. The UV-visible absorption spectra showed high absorption in the UV region and weak absorption in the visible region. An increase in the energy band gap for the maximum absorption peak was observed from 3.49 eV for ZnO to 3.88 eV for Zn0.91Cu0.04Co0.05O. The Burstein-Moss effect explained the noticed blue shift in absorption spectra and energy band gaps. The vibrating sample magnetometer study revealed the change in the diamagnetic behavior of pure ZnO to the ferromagnetic behavior of the prepared nanoparticles at room temperature for different doping concentrations. In the current study, we have developed the room-temperature ferromagnetism (RTFM) for Cu and Co co-doped ZnO nanoparticles. Since RTFM is the key objective for dilute magnetic semiconductors, therefore it can be served as the desirable expectant for spintronics applications with improved functionalities and device concepts.

Effects of Strontium on the Structural, Optical, and Microwave Dielectric Properties of Ba2Ti9O20 Ceramics Synthesized by a Mixed Oxide Route.

Solid solutions of Sr-doped barium nonatitanate (Ba2Ti9O20) ceramics were synthesized by a mixed oxide route, studied their structural, microstructural, optical, and microwave dielectric properties were studied. X-ray diffraction (XRD) has been used to reveal the structure and crystallite size of doped Ba2Ti9O20 ceramics. Rietveld refinements of XRD patterns revealed that all of the ceramics have a tetragonal structure with space group I4/m. The surface morphologies of all the samples were characterized by using scanning electron microscopy (SEM). Fourier transform infrared (FT-IR) studies gave the O-H and Ti-O modes of vibrations. The stretching modes of Ti-O and O-H were noted at 1400, 2960, 3700, and near to 440 cm-1, respectively. The band gap energy decreases with increasing Sr2+ contents, and a high value (2.12 eV) was observed in the base sample. The microwave dielectric properties of the ceramic samples were studied at different frequencies ranging from 1 to 2 GHz by using impedance spectroscopy. The obtained results showed the suitability of these samples for microwave dielectric resonator (antenna) applications.

Effects of Vacuum and Air Annealing on Structural, Morphological, Optical, and Electrical Properties of Multilayer CdZnS Thin Films for Photovoltaic and Optoelectronic Applications.

Multilayer CdZnS (CZS) thin film was deposited on soda lime glass substrates. After deposition, the films were vacuum and air annealed at 100 °C, 200 °C, 300 and 400 °C for 1 h. Effects of vacuum and air annealing on structural, morphological, optical, and electrical properties of multilayer CZS films with increasing annealing temperature (IAT) were studied. The structural analysis revealed that the films were polycrystalline with hexagonal structure having a prominent/intensive peak along the (002) plane at 300 and 400 °C. The crystallite size of nanoparticles increased from 18.4 to 20.5 nm under air annealing and from 18.4 to 26.9 nm under vacuum annealing, showing the significance of annealing on nanoparticle grain growth. According to morphological analysis, the multilayer technique provides homogeneous film distribution over the substrate. The transmittance graphs of films revealed that it increased up to 92% in the visible and NIR regions under vacuum annealing and up to 52% under air annealing. Vacuum annealing enhanced the band gap energies more significantly than air annealing. The electrical resistivity increased with IAT, showing that structural, morphological, optical, and electrical properties of the multilayer thin films of CZS were strongly dependent on vacuum and air annealing.

Sequestration of Anionic and Cationic Dyes through Thermally Activated Slate and Their Kinetics and Thermodynamic Characteristics.

Adsorption is one of the most common and most robust techniques for the decontamination approach of effluents, owing to its design flexibility, simplicity, cost effectiveness, and high efficiency. However, its application is limited on a large scale due to its cost. The current study investigates the use of low-cost, ecofriendly, and ubiquitous thermally activated clay material. Thermally treated clay was used for the adsorption of crystal violet (CV), Congo red (CR), and malachite green (MG) organic dyes from aqueous solutions. Characterization of slate was carried out with Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy, X-ray diffraction, N2 physisorption, and XRF spectrometry. The adsorption process was studied as a function of concentration, time, pH, and temperature. Using the batch adsorption technique, the experimentally obtained adsorption data were fitted to both Langmuir and Freundlich isotherms. The adsorption data followed the pseudo-second-order kinetics, and the adsorption capacity was recorded as 360.12 mg/g for CV, 409.23 mg/g for CR, and 390.14 mg/g for MG. The good uptake is the outcome of a greater surface area (24.751 m2/g) for the slate activated at 873 K. The thermodynamic studies showed that the adsorption process remained endothermic and spontaneous. Thermally activated slate proved itself to be an efficient adsorbent and can effectively be used for the removal of textile dyes from the contaminated water, and it is evident from the good uptake of the adsorbate by the adsorbent.

Hydrothermal Extraction of Amorphous Silica from Locally Available Slate.

Slate is a naturally available aluminous silicate based material and can be used as a good source for silica extraction. In the current investigation, the slate sample was passed through calcination and acid leaching processes to decrease alumina contents and other major constituents. Silica extraction was performed by alkaline hydrothermal treatment of a given slate sample followed by acidic precipitation. Different steps, including the effect of concentration of sodium hydroxide solution, reaction time, the ratio of the mass of sample to volume of alkaline solution, the temperature of dispersion, and pH of the filtrate, were investigated to extract the maximum amount of pure amorphous silica. The extracted silica was physicochemically analyzed through XRF, XRD, FT-IR spectroscopy, and SEM techniques. The amorphous nature of the extracted silica is evident from XRD and SEM studies, while FT-IR studies support its purity, showing peaks of only Si-O-Si bonds. The purity of the extracted silica was further confirmed via XRF spectroscopic analysis and a hydrofluoric acid test.

Structural Elucidation, Electronic and Microwave Dielectric Properties of Ca(Sn x Ti1-x )O3, (0 ≤ x ≤ 0.8) Lead-Free Ceramics.

The lead-free Ca(Sn x Ti1-x )O3, (0 ≤ x ≤ 0.8) sample has been successfully prepared through the ball milling process, sintered at 1200 °C for 3 h. The structural, morphological, vibrational, and microwave dielectric properties of synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and impedance analysis. All the samples have an orthorhombic phase structure with a space group of Pbnm formation, and the crystalline size and strain changes with respect to Sn4+ doping were observed in the XRD analysis. From a morphological point of view, on increasing the content "x", the grain size reduces from 3.29 to 1.37 µm. The existence of vibrations and the bridging stretching mode of Ti-O-Ti and Ti-O-Sn both are associated with the broadband in the region below 800 cm-1 verified by FT-IR. The variation in electrons hopping off the host compound with respect to Sn4+ ions was analyzed in AC conductivity. The changes of dielectric properties such as complex permittivity, modulus spectroscopy, and dielectric loss at room temperature with a different frequency range of 1.00-2.00 GHz are discussed.