Solid-state Reaction Method Research Articles

Advanced energy storage properties and multi-scale regulation mechanism in (1-x)(Bi0.5Na0.5)0.7Sr0.3TiO3-xCa(Nb0.5Al0.5)O3 relaxor ferroelectric ceramics

Since recently, lead-free dielectric ceramics have garnered significant interest for their high-power density and rapid charge-discharge capabilities. Nonetheless, their practical application is still limited by relatively low energy storage density and efficiency. To address this issue, a new class of relaxor ferroelectric ceramics ((1-x)(Bi0.5Na0.5)0.7Sr0.3TiO3-xCa(Nb0.5Al0.5)O3, with x from 0.00 to 0.16) was formulated and synthesized in the present work using a solid-state reaction method. Special attention was paid to the effect of multiscale structure regulation on the energy storage properties of the ceramics. All ceramics exhibited the relaxor characteristics, which increased with the added content of Ca(Nb0.5Al0.5)O3 (CNA). Significant achievements have been made in multi-scale regulation of energy storage characteristics of these ceramics. In particular, the ultrahigh energy storage density and efficiency (10.15 J/cm3 and 86.2 %, respectively) were realized in the ceramic with x = 0.14. This optimized composition also displayed good temperature stability at 20–140 °C and excellent frequency stability in the range of 1–200 Hz. Furthermore, the outstanding charge and discharge characteristics (current density CD, power density PD, and discharge time t0.9 of 1257 A/cm2, 377 MW/cm3, and 45.8 ns, respectively) were obtained. The experimental study, finite element analysis, and first-principles calculations confirmed that the multiscale features, such as nano-scale domains, large band gap, and small grain size, promoted by the addition of CNA, are all beneficial for the improvement of energy storage performance, opening up new prospects in the application of advanced dielectric capacitors.

Investigations of crystallographic, magnetic, optical and photoluminescence nature of Sm2O3 doped SrTiO3 nanomaterials for LED

We used the solid-state reaction (SSR) method to make samarium oxide-doped SrTiO3 perovskite ceramic. We then put the synthesized samples through PXRD analysis to look at their structural properties. It is observed that the Sm-doped SrTiO3 exhibited a cubic phase, with no secondary phase resulting from Sm-doping. For a higher doping concentration (at 5 %) of Sm2O3, we slightly increased the particle size (from 30 nm to 33 nm). HR-SEM is used to study the morphology and nature of each sample. We examined the component composition of Sr, Ti, O, and Sm using the EDAX spectra and matched it with the stoichiometry ratio. FT-IR spectroscopy was carried out to analyze the presence of functional groups and chemical bonding in the samples. We studied the magnetic properties of the synthesized samples at room temperature using the VSM technique. The coercivity, retentivity, and saturation magnetization of SrTiO3 considerably increased with a higher doping concentration of Sm. We used UV diffuse reflectance spectroscopy to record the reflectance spectra and calculate the optical energy values. An increase in Sm-doping concentration red-shifted the absorption peaks. The photoluminescence spectra revealed that the samples exhibited a wide spectrum of colours. The proposed combination of nanomaterials is suitable to become an appropriate candidate for white LED applications.

Optical and electrical conductivity of secondary phase of Sr2+/Ca2+ doped La1-xSrx/CaxNbO4 (0≤x≤0.4)

In the present study, Sr2+ and Ca2+ ions doped lanthanum niobate (LaNbO4) samples are synthesized using the solid-state reaction method. The effect of sintering temperature on physical, optical and electrical properties are investigated of the pristine and Sr2+/Ca2+ doped LaNbO4 samples using by characterization facilities such as X-ray diffraction, Fourier transform-infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy & energy-dispersive spectroscopy, UV–Vis spectrophotometer. The observed monoclinic phase is confirmed by XRD. The optical bandgap of LNS samples (3.11 eV–2.08 eV) and LNC samples (2.95 eV–2.86 eV) are calculated. The electrical conductivity of the Sr2+/Ca2+ doped LaNbO4 samples are evaluated by using and Impedance analyzer from ambient temperature to 900 °C, where, the highest conductivity (1.01 × 10−1 Scm−1 at 900 °C) is observed for LNS-4 with 80 % relative density due to presence of higher oxygen vacancies. It is observed that the Sr2+ doping is more effective than Ca2+ doping for enhancing the protonic conductivity of the LaNbO4 system. The doping of Sr2+ and Ca2+ ions is indicated that Sr2+ based polymorphic composites could be more effective electrolytes for solid oxide fuel cell (SOFCs) applications.

Red-emitting Mn4+-doped Li2MgSn2O6 phosphors for plant growth LED lighting

In this study, a novel red-emitting Mn4+ doped Li2MgSn2O6 (Li2MgSn2O6:Mn4+) phosphors were successfully synthesized using a simple solid-state reaction method. XRD patterns indicated the replacement of Mn4+ ions with Sn4+ ions in the [SnO6] octahedrons site of the Li2MgSn2O6 lattice, and XPS spectra confirmed the Mn4+ oxidation state. Excited at 323 nm and 480 nm, the phosphors exhibited a strong red emission band peaking at 659 nm, attributed to the 2E → 4A2 transition of Mn4+ ions. Notably, the highest PL intensity was found in the Li2MgSn2O6:0.3%Mn4+ sample annealed at 1000 °C. These phosphors, with a particle size of 1.0 μm, possess a long lifetime of 0.176 ms, high activation energy of 0.335 eV, excellent color purity of 99.9%, and good internal and external quantum efficiency of 44.5% and 24.1%, respectively. Furthermore, an LED coated with Li2MgSn2O6:0.3%Mn4+ phosphor on a 365 nm NUV LED chip showed strong emission matching the absorption spectrum of the red phytochrome. Therefore, these results indicated that the synthesized Li2MgSn2O6:Mn4+ phosphors could be used as red-emitting materials for plant growth LED applications.

Insights into the preparation and photoluminescence properties of MgTi2O5: Eu3+ red phosphor with high color purity for w-LED applications

As one of the critical components for achieving high-quality white light emitting diodes (w-LEDs) are efficient phosphors, a series of intense red emitting Eu3+doped magnesium dititanate (Mg(1-x)Ti2O5: xEu3+; x = 0, 0.005, 0.008, 0.01, 0.02 and 0.03 mol) phosphors were prepared via solid-state reaction method. The X-ray diffraction (XRD) patterns confirmed the phase purity and orthorhombic structure of the prepared phosphors. The Ti-O functional groups were detected from the Fourier transform infrared (FTIR) spectra and Field emission scanning electron microscopy (FESEM) images revealed agglomerated spherical-like shaped phosphor particles. Under 465 nm excitation, intense red emission corresponding to 5D0→7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+ ions were recorded in the photoluminescence (PL) spectra with an intense peak at 615 nm. The optimum concentration of Eu3+ ions was determined to be 1 mol% and the concentration quenching mechanism was due to the interaction between adjacent Eu3+ ions. The lifetime values of the samples were in the millisecond range and the internal quantum efficiency was determined to be 31.65 %. The Commission Internationale de l'Eclairage (CIE) coordinates of the optimum sample Mg0.99Ti2O5:0.01Eu3+ are (0.6421, 0.3575), lies in the red region with 99.9 % color purity and have warm correlated color temperature (CCT) values. Therefore obtained results suggest that the prepared Mg(1-x)Ti2O5:xEu3+phosphors can be used as an efficient red phosphor for w-LED applications.

Mechanism and dynamic analysis of persistent luminescence in phosphors Sr2MgSi2O7: Eu2+, Dy3+

The persistent luminescent (PSL) phosphors Sr2-x-yMgSi2O7: xEu2+, yDy3+ (x = 0∼0.08, y = 0∼0.08) were synthesized by a solid-state reaction method in a weak reductive atmosphere of 5%-H2/N2. Comprehensive measurements were carried out to study the effects of Eu2+ and Dy3+ doping amount on the crystal phase, photoluminescence (PL), afterglow decay properties, and trap energy levels. The results indicated that the impurity phases decreased and disappeared, and crystalline grains tended to be larger and denser with the doping amount of Eu2+ and Dy3+ increasing. We shed light on the origination of asymmetric PL peak, concentration quenching of Eu2+ ions, time evolution of PSL specture and chromaticity of Eu2+, Dy3+ co-doped phosphors. Based on the deconvolutions of X-ray photoelectron spectroscopy (XPS) spectra and thermoluminescence (TL) spectra, the types and energy depth of traps in these phosphors were systematically studied. According to the data of PL, PLE, and TL, we deduced a schematic diagram of the energy level and discussed the mechanism of PSL of the phosphors. As Dy3+ dopant increases, the Eu2+, Dy3+ co-doped phosphors not only generate more defects of VO•• and VSrʺ, but also introduce DySr• defect with proper trap depth, meanwhile, a thermally assisted tunneling mechanism will gradually dominate during the persistent luminescence, which is responsible for that the phosphor with x = 0.02, y = 0.01 presents the best long afterglow property.

A remarkable permeability enhancement of Ni1−xZnxFe2O4 (x = 0.65 and 0.70), using a multi-compound calcined additive

In this study, entanglement of composition, additive and/or sintering conditions and their effects on magnetic properties of soft ferrites, nickel zinc spinel ferrites (Ni1−xZnxFe2O4, x = 0.65 and 0.70) which were prepared via conventional solid-state reaction method investigated. Also an equiponderant calcined mixture of Bi2O3, CaO, CeO2, SiO2, Al2O3, Y2O3 and nanotitania was mixed thoroughly and used as a multi-compound calcined additive (MCCA). Calcined ferrite powders were crushed, dry and wet milled, dried, mixed with different amounts of MCCA (0.0, 0.5, 1.0, 1.5 and 2.0 wt%), formed in toroidal shapes and finally sintered at different temperatures, from 1150 up to 1360 °C for 3 h. X-ray diffraction assessment confirmed formation of the single phase cubic spinel structures. Initial permeability and Q-factor spectra of the toroids were obtained from 0.1 to 1000 kHz, using an LCR meter. The results show that initial permeability of each sample has a maximum and addition of MCCA to the ferrites leads to a marvelous increase in permeabilities. Additionally, MCCA decreases the optimum sintering temperature too. The optimum amounts of additive were 1.0 and 0.5 wt% for the x = 0.65 (μ′ = 492, Ts = 1280 °C) and x = 0.70 (μ′ = 478, Ts = 1320 °C), respectively. Permeability spectra illustrate that utility zone of the Ni0.35Zn0.65Fe2O4 and Ni0.3Zn0.7Fe2O4 are both less than 100 and 10 kHz, respectively. The results represent that there is a strong entanglement between composition, additive and/or sintering conditions. It can be concluded the MCCA added Ni0.35Zn0.65Fe2O4, is suitable for application in the switching power supplies.

Effects of TiO2 on the mechanical and physical properties of Fe2O3-Doped Yttria-Stabilized Zirconia for electrolyte of Solid Oxide Fuel Cells

Yttria-Stabilized Zirconia (YSZ) based electrolytes of Solid Oxide Fuel Cell (SOFC) are widely used due to their higher ionic conductivity, stability, and availability. The present study focuses on improving the performance of YSZ-based electrolytes particularly by doping other particles into YSZ. TiO2 was doped into Fe2O3-8YSZ composite and the effects of TiO2 on the mechanical and physical properties of the composites were observed. The concentrations of TiO2 were varied by 0 wt%, 1 wt%, 3 wt%, and 5 wt% for different compositions of the composites. The samples were fabricated by the solid-state reaction method by pressing the powders at 250 MPa for 3 min and were sintered at 1250 °C for 4 h. The sintered samples were then undergone through characterization tests in terms of percentage of volume shrinkage, density, porosity, Diametral Tensile Strength (DTS), and microhardness. The highest values of volume shrinkage (34.83%), relative density (97.83%), DTS (36.58 MPa), hardness (965 HV), and the lowest porosity (2.17%) were found for 5 wt% TiO2 addition. Besides, the lowest values of volume shrinkage (28.44%), relative density (87.94%), DTS (3.24 MPa), microhardness (340 HV), and the highest porosity (12.06%) were found for Fe2O3-8YSZ composites without (0 wt%) TiO2 addition.

Huge enhancement in upconversion luminescence near-infrared emission of KYb (MoO4)2: Er3+ phosphor by doping Y3+ ions

The KYb(MoO4)2: Er3+, Y3+ phosphors were synthesized by high temperature solid state reaction method. By further doping Y3+ ions, the near-infrared (NIR, 804 nm, 4I9/2 → 4I15/2) luminescence of KYb(MoO4)2: 0.1 % Er3+ phosphor is greatly enhanced. Based on the upconversion luminescence (UCL) spectra, the optimal doping concentration of Y3+ ions were 7.5 %. Its near-infrared UCL intensity is about 26.9 times that of undoped Y3+ ions. Through a series of characterization methods, we find that the enhancement of NIR upconversion emission is due to the generation of defect bands. It plays a crucial role in facilitating the transfer of energy from green light level (2H11/2, 4S3/2) to red light level (4F9/2) and near-infrared level. To explain the luminescence mechanism, the power dependence, UV-VI-NIR absorption spectra, excitation spectra at 804 nm and emission spectra at 380 nm were studied. In addition, the 804 nm single near-infrared UCL intensity of KYb (MoO4)2: Er3+, Y3+ shows a linear variation with temperature in the temperature range of 298 K–673 K. The maximum sensitivity is 0.13 % K−1. This study provides a new method and theoretical support for the application of near-infrared UCL in optical temperature measurement.

Synthesis and characterization of pristine CuO and Mg/CuO nanostructures for their anti-breast cancer and photocatalytic degradation applications: Experimental and DFT investigations

The present manuscript emphasizes the versatility of Mg-doped CuO nanostructures for environmental remediation (photocatalytic degradation of pollutants) and biomedical applications (anticancer activity) thus highlighting their potential impact in addressing societal and health challenges. The primary focus of the manuscript is the synthesis, characterization, and applications of Mg-doped CuO nanostructures. In order to meet this purpose, pure and Mg doped CuO nanostructures were synthesized using the solid-state reaction method and ball milling techniques. To characterize the prepared samples, X-ray diffraction, transmission electron microscopy, UV-Visible, photoluminescence, and Raman spectroscopy techniques were utilized. A profusion of structural defects and the reduction in crystallite size have been observed in CuO nanomaterial’s due to the dopant's complete incorporation into the CuO lattice. Additionally, the band gap of CuO has been observed to decrease as a result of Mg doping. Density functional theory was employed to simulate the effect of Mg on the properties of CuO. The efficiency of photocatalytic degradation aided by sunlight against methylene blue increased from 50.8 % to 89.5 %. MCF-7, a cell line representing human breast adenocarcinoma, was utilized to assess the cytotoxicity of Mg/CuO samples. CuO nanoparticles enriched with Mg are viable biocompatible anti-cancer agents and prospective photocatalyst for the removal of environmental pollutants from aqueous solutions, according to the findings of this study.

Solid-state green synthesis of two (1:1) organic intermolecular compounds; their physico-chemical, thermal, single crystal growth, and atomic packing studies

The solid-state solvent free reaction method has been adopted for the one-pot synthesis of novel organic materials with utmost 100 % yield. To identify the composition forming the intermolecular compound (IMC), the solid-liquid equilibria of entire compositions have been studied by establishing the phase diagram of n, n-dimethylaminobenzaldehyde (DMAB) with anthranilamide (AN) and 2-chloro-4-nitro benzoic acid (CNBA). The structural changes and novelty of the IMCs to that of parents are studied using FTIR, NMR and X-ray diffraction. The studies of optical properties of intermolecular compounds using UV–vis absorption and fluorescence spectroscopy infer the significant fluorescence emission. The single crystals of both intermolecular compounds, ANDMAB and DMABCNBA, are grown from solution using slow evaporation technique. The single crystal X-ray diffraction studies reveal that IMC of AN and DMAB is a racemic mixture whereas IMC of DMAB and CNBA is a co-crystal, and both the crystals have crystallized in triclinic P1‾ space group. The thermal stability and thermal behaviors are also studied using the experimental heat of fusion values obtained from differential scanning calorimetry (DSC).

Redox Stability and Electrical Properties of a Series of Novel Quadruple Dopant BIMEVOX: Bi2V1−4x(CuNiNbTi)xO5.5−δ

Bi2VO5.5‐based materials are well‐known oxide ion conductors owing to their exceptionally high ionic conductivity. However, their poor phase and redox stabilities under a reducing atmosphere hinder their practical application as electrolytes for solid oxide fuel cells. Here, a series of novel quadruple metal‐doped bismuth vanadium system materials Bi2V1−4x(CuNiNbTi)xO5.5−δ (0 ≤ x ≤ 0.1) are prepared through a traditional solid state reaction method, aiming to enhance the phase and redox stability under reducing atmosphere. The results reveal that multiple‐metal‐doping can stabilize the tetragonal phase of Bi2VO5.5 to room temperature and show good phase and structural stabilities under inert or high oxygen partial pressure atmospheres, as well as pure oxide ion conduction which is slightly lower than that of the parent material. However, under a reducing environment, the Bi2V1−4x(CuNiNbTi)xO5.5−δ materials would still undergo a phase decomposition, yielding elemental bismuth impurity, and introducing strong electronic conduction. Thus, how to improve the phase and redox stabilities under the reducing atmosphere of the Bi2VO5.5‐based materials is still the endeavor direction in the future.

Phase transition, structural and magnetic parameters of vanadium-substituted Bi0.9Sm0.1FeO3 multiferroic ceramics

ABSTRACT The inorganic multiferroic compounds Bi0.9Sm0.1Fe1 − x V x O3 (x = 0.0, 0.015, 0.03, and 0.045) were prepared by the solid-state reaction method. X-ray diffraction analysis confirmed the rhombohedral perovskite-like structure with minor traces of the impurity phases Bi2Fe4O9 and Bi25FeO40. The lattice parameters a and c, and the volume of the hexagonal unit cell were extracted from the X-ray diffraction data and found to increase as the V5+ content is increased. The average crystallite size was estimated to be in the range 380–415 Å. Fourier transform infrared spectroscopy confirmed the rhombohedral perovskite-like structure via the vibration bands of the octahedral FeO6 group observed between 410 and 570 cm−1. A differential scanning calorimeter was used to record the thermal scans which revealed that the compounds have undergone crystalline phase transitions at temperatures in the range 300–320°C. A 4.5% V + 5 substitution has shifted the transition peak by 20°C. The magnetic hysteresis loops taken at room temperature with a vibrating sample magnetometer revealed the ordinary ferromagnetic behavior. The V5+ substitution enhanced the remanent magnetization, but the magnetic coercivity was found to fluctuate around an average value of about 1000 Oe. The compound Bi0.9Sm0.1Fe0.955V0.045O3 exhibited the maximum remanent magnetization.

“Template-assisted synthesis” strategy to improve the bifunctional catalytic activity of oxygen electrode for reversible protonic ceramic electrochemical cell

Reversible protonic ceramic electrochemical cell (R-PCEC) is a new energy conversion device that can achieve efficient conversion between chemical energy and electrical energy. However, the oxygen electrode has poor activity towards oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which hinders the large-scale application of R-PCEC. Therefore, in order to improve the catalytic activity of oxygen electrodes, La0.5Sr0.5Co0.2Fe0.8O3 (LSCF) is prepared using mesoporous silica SiO2 (SBA-15) and polymethyl methacrylate (PMMA) as templates, and it was combined with BaZr0.1Ce0.7Y0.2O3-δ (BZCY) to form a composite oxygen electrode for R-PCEC. Compared to the LSCF with solid-state reaction method, LSCF with hard-template method shows higher specific surface area and more oxygen vacancy, resulting in excellent ORR catalytic activity. In addition, LSCF prepared using PMMA as a template exhibits the best ORR catalytic activity, and the single cell with this composite oxygen electrode shows the highest maximum power density of 406 mW cm−2 in fuel cell (FC) mode with wet H2 (3%H2O) and air as the fuel and oxidant, respectively. Additionally, it demonstrates a current density of −973 mA cm−2 at 1.3 V in electrolysis cell (EC) mode with wet air (10%H2O) as the oxidant. The single cell also shows good reversibility in FC mode and EC mode. This work provides a new strategy to improve the bifunctional activity of oxygen electrode in R-PCEC.

Optimizing the curie temperature of La0.67Sr0.33MnO3–based composite materials around room temperature through the addition of Mo, Mn, and Ni metallic elements

Our study sheds light on the role of secondary phases in optimizing the magnetic properties of LSMO, offering valuable insights into the relationship between impurity phases, Curie temperature (TC), and magnetic entropy change. To achieve this goal, the Mn, Ni, and Mo elements were individually incorporated into the LSMO matrix to the formation of secondary phases. The solid-state reaction method was employed to create composite materials of (0.8)La0.67Sr0.33MnO3 + (0.2)A (A=Mn, Ni, and Mo). XRD and SEM results confirmed the successful formation of impurity phases within the main LSMO phase. From temperature-dependent magnetization (M(T)) measurements, it was determined that the TC of the samples approach towards room temperature with the existence of impurity phases. Additionally, the relationship between electron bandwidth (W) and TC was examined. The lowest TC value was observed for the lowest value of W. Besides these, the effect of the formation of impurity phases on the maximum magnetic entropy change (-ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{M}^{max}$$\\end{document}) value is examined, and it is seen that impurity phases cause a decrease in the (-ΔSMmax)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(-\\Delta {S}_{M}^{max})$$\\end{document} values.

Enhanced permittivity of Lu-doped SrTiO3 ceramics sintered in air atmosphere through defect chemistry

A series of Sr1‒1.5xLuxTiO3 (x = 0, 0.005, 0.01, 0.015, and 0.02) ceramics was sintered under an air atmosphere through the solid-state reaction method. The results show that doping with Lu3+ considerably enhances material permittivity. The ceramic with x = 0.01 exhibits a colossal permittivity (CP) of ∼101000 with a tanδ of ∼0.16 at a frequency of 1 kHz, demonstrating enhanced stability over a wide temperature (30 to 300 °C) and frequency (102 to 106 Hz) range. Based on the analysis of dielectric relaxation, X-ray photoelectron spectroscopy (XPS), and the universal dielectric response law, the CP effect is primarily due to the formation of defect dipoles, which are correlated with the presence of oxygen vacancies, such as Ti3+ Ti3+, , Ti3+, and Ti3+. These defect dipoles serve to pin electrons, limiting long-range transitions, and enhancing local polarization. Doping with Lu3+ also induces a secondary Lu2Ti2O7 phase, which are characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The results generated in this study can inform the development and application of new CP materials based on SrTiO3.

The Stabilization of Copper and Cadmium in The Hydrated CaO-CuO-SiO2 and CaO-CdO-SiO2 Composites

The stabilization of toxic metals in the stable matrices is quite well-known. Research on copper and cadmium stabilization in the CaO-CuO-SiO2 and CaO-CdO-SiO2 composites was conducted to study the characteristics of CaO-CuO-SiO2 and CaO-CdO-SiO2 composites as well as the Cu and Cd metals stabilization in the hydrated composites. The composites of CaO-CuO-SiO2 and CaO-CdO-SiO2 were synthesized by the solid-state reaction method. A stoichiometric amount of CaO, SiO2, Cu(NO3)2, and CdO were calcined at 1050°C for 4 hours. The synthesized compounds were further hydrated in a soaking time of 30, 60, and 90 days. The hydration produced calcium silicate hydrate that can stabilize metals. The Cu and Cd stability in CaO-CuO-SiO2 and CaO-CdO-SiO2, respectively, were tested using the Toxicity Leaching Procedure (TCLP) method. The hydrated and hydrated composite characterizations were performed using X-ray diffraction (XRD), Fourier Transform Infra-Red Spectrophotometer (FTIR), and Scanning Energy Mocroscopy-Energy Dispersive X-ray analyzer (SEM-EDX) and the Atomic Absorption Spectroscopy (AAS) methods. The composites mainly consist of Ca3SiO5, Ca2SiO4, Ca(OH)2, SiO2, and metal oxide of CuO, Cu2O, and CdO. The composites were able to stabilize ~100% of the heavy metals of Cu and Cd.

Fabrication of flexible (Mg0.2Al0.2Fe0.2Ni0.2Co0.2)2Ti2.8O8 ceramics via compositionally complex ceramics method

A novel compositionally-complex flexible (Mg0.2Al0.2Fe0.2Ni0.2Co0.2)2Ti2.8O8 (abbreviated as CCC) ceramic with pseudobrookite structure was synthesized by solid-state reaction method. As compared to the fabrication process of flexible aluminum titanate ceramic (C. Babelot, 2011), the sintering temperature was significantly reduced from 1600 °C to 1200 °C by co-doping. And, the combinations of displacement (0.11–0.25 mm) and bending strength (10–40 MPa) were achieved by controlling the sintering condition. Among these, the specimen sintered at 1200 °C for 2 h (abbreviated as CCC-1200-2) presents a single-phase crystal structure and uniform elemental distribution. After that, its near-zero thermal expansion coefficient of 0.47 × 10−6 K−1 at low temperature was obtained and the nonlinear thermal expansion behavior was observed. Lastly, the thermal stability of sample CCC-1200-2 was checked out by annealing the samples between 900 °C and 1600 °C for various times up to 100 h. As a result, this study successfully fabricated the flexible CCC ceramics with improved mechanical properties, high thermal stability, and low sintering requirements, providing a new technology strategy for pseudobrookite-type ceramics and compositionally-complex ceramics fabrication.

Efficient broadband NIR emission of Yb3+-activated double-perovskite tungstate Ba0.5MgLaWO6☆

Broad-band near-infrared (NIR) phosphors have garnered increasing attention due to the versatile applications in spectroscopy technology fields, but the choice of efficient NIR phosphors remains a challenge. Here, Yb3+-activated cubic double-perovskite tungstate Ba0.5MgLaWO6 was synthesized using a solid-state reaction method. A broadband NIR emission (800–1150 nm) is observed from the 2F5/2→2F7/2 transition of Yb3+ activators in Ba0.5MgLaWO6 under the excitation by UV and near-UV light. Photoluminescence (PL) spectra, decay and emission lifetimes, concentration-dependent intensities, and low temperature luminescence of Yb3+-activated Ba0.5MgLaWO6 were investigated to study the energy transfer (ET) from isolated WO6 polyhedra to Yb3+ activators. The main luminous mechanism involves cooperative energy transfer (CET), wherein, one high-energy excitation photon absorbed by host WO6 group converts to two NIR photons emitted by Yb3+. The partial substitution of Mo6+ for W6+ in Ba0.5MgLaWO6 further leads to a significant increase of the intensity and lifetime of the NIR luminescence. This work provides a feasible strategy for developing a new Yb3+-doped perovskite tungstate, which demonstrates efficient wavelength down-conversion from UV and near-UV to NIR. This material could find versatile applications as an effective NIR luminescent candidate.

Enhancement of dielectric performance in tungsten bronze ceramics by substituting 25 % of Gd into Sr2SmTi2Nb3O15 ceramic

This study investigates the synthesis and systematic examination of tungsten bronze ceramics Sr2GdxSm1-xTi2Nb3O15 (SGSTN, x = 0, 0.25, 0.5, 0.75) using the solid-state reaction method. X-ray diffraction revealed tetragonal tungsten bronze structures with space group P4/mbm for x = 0.25, 0.5, and 0.75, and P4bm for x = 0. Scanning electron microscopy showed high densification and uniform grain dispersion, with grain sizes ranging from 6.2 to 10.8 μm depending on the Gd content. Impedance spectroscopy demonstrated that the dielectric properties were influenced by the addition of Gd3+, with a dielectric constant of 2549.97 at 400 °C and 1 kHz for x = 0.25. Impedance analysis suggested a negative temperature coefficient of resistance (NTCR), and Cole-Cole plots showed single semicircular arcs. Activation energy increased with decreasing (A1)-site ion size, indicating that oxygen vacancies were responsible for the relaxation phenomena. Complex modulus analysis confirmed the presence of non-Debye relaxations in the material.