X-ray Diffraction Rietveld Analysis Research Articles

Superconductivity investigation of (Bi, Pb)-2223 added with different nanoferrites and their composites

In this study, the impact of different types of nanoferrites additions of Zn0.5Ni0.5Fe2O4 and Ba0.4Sr0.4Ca0.2Fe12O19 nanoparticles and their nanocomposite of (Zn0.5Ni0.5Fe2O4)0.5 (Ba0.4Sr0.4Ca0.2Fe12O19)0.5 on the structural and normal state resistivity of Bi1.6Pb0.4Sr2Ca2Cu3O10, ((Bi,Pb)-2223) superconducting phase were systematically investigated. The samples were synthesised using high purity oxide powders via a solid-state reaction approach. Based on the Rietveld analysis of x-ray diffraction (XRD) data, the tetragonal structure of (Bi,Pb)-2223 was established to be the predominant phase for all composite samples of the three nano-additions’ contents. However, a little change to the lattice parameters ( a and c ) was obtained. Furthermore, the small amounts (0.04 wt%) of Ba0.4Sr0.4Ca0.2Fe12O19 and (Zn0.5Ni0.5Fe2O4)0.5(Ba0.4Sr0.4Ca0.2Fe12O19)0.5 improved the development of the (Bi,Pb)-2223 phase. The volume fraction of the (Bi,Pb)-2223 phase increased from 86.47% to 88.73% and 88.69%, respectively. Then, it declined to 74.25% and 71.48% upon rising x to 0.40 wt%, respectively, as well as for Zn0.5Ni0.5Fe2O4 nanoparticles up to 0.40 wt%. SEM images verify the host superconducting matrix’s granular structure for all three nanoadditions up to 0.40 wt%. The existence of three nano additions in the host superconductor matrix is verified by employing energy dispersive x-ray (EDX) and x-ray photoelectron spectroscopy (XPS) analysis. The measurements for the resistivity dependency of temperature presented that, as compared to the pure sample (Tc = 108.67 K), the nano-(Zn0.5Ni0.5Fe2O4) x added in the (Bi,Pb)-2223 phase exhibits more negative impact than it is with the other two additions. In contrast, the nano-(Ba0.4Sr0.4Ca0.2Fe12O19) x has the highest value of Tc with a value of 110.95 K at x = 0.04 wt%. Furthermore, the superconducting transition width (∆Tc) improved for all composite samples except for the sample at x = 0.04 wt%, for Ba0.4Sr0.4Ca0.2Fe12O19 and (Zn0.5Ni0.5Fe2O4)0.5 (Ba0.4Sr0.4 Ca0.2Fe12O19)0.5 which showed the sharpest transition width. This suggests that their addition is anticipated to act as artificial pinning centers and strengthen the coupling between the grains in the (Bi,Pb)-2223 ceramic.

Characterization of dielectric and piezoelectric responses in 0.76(Na0.5Bi0.5)TiO3-0.06BaTiO3-0.18(K0.5Bi0.5)TiO3 ceramics synthesized by the solid-state method

In this research, the authors explore the structural, dielectric, electrical insulating, electromechanical, and piezoelectric characteristics of ceramics that have been modified using BaTiO3 and (K0.5Bi0.5)TiO3.as key components. Specifically, they explore the composition (1-x-y)(Na0.5Bi0.5)TiO3-xBaTiO3-y(K0.5 Bi0.5)TiO3, where x (mol.%) varies between 0, 6, and NBT, and y (mol.%) varies between 0, 18, and KBT. These ceramics were fabricated using a solid-state synthesis technique. The optimized calcination temperature for achieving a pure perovskite phase was determined to be 1000 °C for a duration of 4 h. The research involves a comprehensive analysis of the composition, microstructure, electrical insulating, and electromechanical characteristics of the ceramics. Rietveld analysis of X-ray diffraction (XRD) data was employed to accurately ascertain the morphotropic phase boundary (MPB) within this material. In this paper, we discuss the impact of crystallite size on the shifts in Raman band frequencies. Sintering at 1100 °C for 4 h was found to enhance densification, with scanning electron microscopy (SEM) images illustrating a nearly uniform distribution of compact grains. Electrical insulating assessments demonstrate that each of the ceramics displays a scattered phase transition around the temperature Tm, with a diffusivity ranging from 1.4 to 1.8, and a shift of Tm towards elevated temperatures. Exceptional piezoelectric properties were observed at the morphotropic phase boundary (MPB), including a d33 value of 149 pC/N and electromechanical coupling factors kp of 0.297. These findings are attributed to the coexistence of rhombohedral and tetragonal phases, as well as precise grain size control. This research presents a novel approach to enhancing lead-free ferroelectric materials based on the composition 0.76(Na0.5Bi0.5)TiO3-0.06BaTiO3-0.18(K0.5Bi0.5)TiO3.

Samarium-modified NBT ceramics: a comprehensive exploration of cumulative effects

In the present report, ceramic specimens of sodium bismuth titanate [Na0.5(Bi1-xSmx)0.5TiO3] were prepared through solid-state reaction method with variations in the dopant concentrations specifically, x = 0.0, 0.1, 0.3, 0.5. The structural, optical, mechanical, and magnetic properties of lead-free NBT ceramics were investigated. The rhombohedral phase with space group R3c was confirmed in all prepared ceramic samples using X-ray diffraction patterns and Rietveld analysis. SEM micrographs and Energy Dispersive x-ray spectroscopy (EDAX) assess the morphology, grain size, overall structure, and stoichiometry of the developed compounds. FTIR spectroscopy was used for characterizing and identifying the functional groups. UV–vis spectroscopy revealed that band gap values decreased as dopant concentration increased, confirming the use of NBT-based perovskite as a photoactive material. PL spectra at room temperature exhibited reddish-orange emission. Colour coordinates and CCT values are in the range of 3483 K to 5912 K. At a concentration of x = 0.3, the materials displayed a high Vickers hardness of 8.20 GPa and exhibited minimal wear with low frictional coefficient values. Ferromagnetic behaviour at room temperature (RTFM) was detected in Sm-modified ceramic samples, as confirmed by the VSM study. The cumulative effect impact of the rare earth dopant cation at the Bi-site of NBT was widespread and demonstrated significant potential for use in optoelectronic devices.

Effect of bismuth deficiency with K substitution for Na on piezoelectric properties and crystal structure of Bi0.5−x(Na0.8−yK0.2+y)0.5TiO3–3x/2 (0 ≤ x ≤ 0.015, 0 ≤ y ≤ 0.1) ceramics

The piezoelectric properties and crystal structure of Bi0.5−x(Na0.8−yK0.2+y)0.5TiO3–3x/2 (0 ≤ x ≤ 0.015, 0 ≤ y ≤ 0.1) ceramics were characterized in this study. The crystal-structure refinement for Bi0.5−x(Na0.8K0.2)0.5TiO3–3x/2 was carried out using synchrotron X-ray diffraction data and Rietveld analysis and revealed the coexistence of rhombohedral (R3c) and tetragonal (P4mm) phases for the compositions with 0 ≤ x ≤ 0.015, although the fraction of these phases was almost independent of the composition x (49% for the rhombohedral phase and 51% for the tetragonal phase at x = 0.015). The Bi deficiency led to an increase in the lattice distortion of rhombohedral phase and a decrease in the that of tetragonal phase. The piezoelectric constant (d33) value decreased from 151.5 to 120.6 pC/N as x was increased from 0 to 0.015, and a shift of the depolarization temperature to higher temperatures was also confirmed by in situ d33 measurements. These results are attributed to an increase in the lattice distortion of rhombohedral phase enhanced by the Bi deficiency. The K substitution for Na in Bi0.485(Na0.8−yK0.2+y)0.5TiO2.9775 led to the formation of a morphotropic phase boundary (MPB) in the composition range 0 ≤ y ≤ 0.06, resulting in an increase in the fraction of the tetragonal phase. Although a decrease in the mechanical quality factor (Qm) was observed for K-rich compositions, the highest d33 value of 195.4 pC/N with a mechanical coupling factor of 32.9% was obtained for the Bi0.485(Na0.76K0.24)0.5TiO2.9775 (y = 0.04) ceramic because of the enhancement of the tetragonality in the MPB region, resulting in the onset of depolarization at ∼170 °C.

Photoluminescence features of trivalent holmium doped Ca2La8(SiO4)6O2 phosphors

Abstract This study examines the optical properties of Ca2La8−x (SiO4)6O2:xHo3+ phosphors derived using the sol–gel method. X-ray diffraction data and Rietveld analysis confirmed that the phosphors formed in hexagonal phase with an average estimated crystalline size of 27 nm. The prominent excitation peak observed at wavelength 463 nm corresponding to excitation energy 2.68 eV was due to the 5I8 → 5G6 + 5F1 transition. The photoluminescence emission spectra revealed that the synthesized phosphors emitted in the green color region with the 5S2 + 5F4 → 5I8 transition, releasing 2.27 eV energy. The emission and excitation analyses revealed the presence of concentration quenching as the Ho3+ concentration exceeded 0.03 mol in the Ca2La8−x (SiO4)6O2:xHo3+ series. Further, photometry analysis demonstrated a color purity exceeding 94 %, which supports the candidacy of these phosphors for solid-state lighting applications.

Synthesis and crystal structure of a novel quaternary Zr3TiSiC3 MAX phase

A novel quaternary 413-type Zr3TiSiC3 MAX phase has been synthesized in 97% yield by the vacuum carbosilicothermic reduction (VCSTR) method using mixtures of TiO2, ZrO2, SiC, and C powders as starting materials. The crystal structure of the synthesized Zr3TiSiC3 was studied by X-ray diffraction Rietveld analysis. The lattice constants of Zr3TiSiC3 MAX phase were a = 0.328292(5) nm and c = 2.39651(6) nm. It was revealed that the distribution of Zr and Ti atoms was fairly uniform in the basal plane of lattice, but was markedly inhomogeneous along the c-axis, with Zr atoms preferentially occupying the inner layers in the [M4X3] blocks rather than outer layers. The occupations of the outer and inner layers by Zr atoms were found to be approximately 67.4% and 82.6%, respectively, indicating a rather poor chemical ordering of Zr and Ti atoms in metal sublattice of Zr3TiSiC3 MAX phase.

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Numerous studies show that sulfating titania narrows its band gap, facilitating longer-wavelength photochemistry, but there are contradictory reports on whether this improves or degrades UV photocatalysis and whether reactions proceed via electron- or hole-mediated pathways. The widely proposed role of sulfur is that it induces deep electron traps, which increase hole lifetimes. There is, however, no direct evidence for unoccupied states deep in the band gap. By contrast, transient absorption spectroscopy indicates that sulfur induces hole traps. We present experiments on sulfur-free and sulfated titania in which dissociation of hydrogen generates electrons that fill the lowest unoccupied states. The energy of these electrons relative to the conduction band minimum (CBM) was measured with diffuse reflectance spectroscopy in the infrared and UV–vis ranges. For all commercial sulfur-containing anatase materials, conversion of tridentate sulfate species into sulfur substituted on lattice sites occurred under highly oxidizing conditions above 400 °C and led to partially unoccupied states ∼2.8 eV below the CBM. We assign this deep trap state to sulfur atoms substituted on a titanium lattice site with a formal charge of S5+ in non-stoichiometric TiO2+x, based on agreement between the experiment and the predicted UV–vis spectrum of Harb, Sautet, and Raybaud, using HSE06 density functional perturbation theory. Our band structure calculations demonstrate that titanium vacancies (or excess oxygen) are necessary to create partially unoccupied states, and X-ray diffraction Rietveld analysis confirms the existence of these vacancies. The partial occupancy of these states, along with sulfur’s ability to switch oxidation states, explains their role as both electron (S5+ + e– → S4+) and hole (S5+ + h+ → S6+) traps, reconciling previous work. We discuss how relative rates of electron vs hole trapping can enhance or degrade activity depending on the pathway and the TiO2+x non-stoichiometry. We consider how increasing the dopant concentration can induce band bending or pin the Fermi level and shift the redox reactions that are thermodynamically accessible.

Probing the optical and magnetic modality of multi core-shell Fe3O4@SiO2@β-NaGdF4:RE3+ (RE = Ce, Tb, Dy) nanoparticles

A robust yellowish-green emitting multi core-shell Fe3O4@SiO2@β-NaGdF4:RE3+ (RE = 5% Ce, 5% Tb, x% Dy; x = 1, 5 and 10 mol.%) nanoparticles (NPs) containing both magnetic and luminescence modalities, are synthesized using simple, fast and efficient microwave-assisted hydrothermal method. The Rietveld analysis of X-ray diffraction and high-resolution transmission electron microscopy provides an average crystallite size of ∼30 nm, confirming the successful coating of the β-NaGdF4 hexagonal phase over Fe3O4. The detailed photoluminescence investigation suggests a down-converting energy transfer process, Ce3+→Gd3+→Tb3+↔ Dy3+ in which Gd3+ ions play a significant intermediate role assisted by Tb3+. The excitation spectra consist of dominant broadband at ∼252 nm due to Ce3+ (4f–5d), two sharp lines at ∼ 271 nm, and ∼311 due to Gd3+ (8S7/2→6IJ and 6PJ), and frail f−f transitions due to Tb3+ and Dy3+ ions. The excitation at ∼252 nm fetches weak and sharp emission of Gd3+ ions at 310 nm, weak broad emission of Ce3+ (300–400 nm), and strong emission color lines of RE3+ (400–700 nm) due to characteristic transitions of Tb3+ (5D4→7FJ, J = 6–3), and Dy3+ (4F9/2–6H15/2, 6H13/2), respectively. The quenching phenomenon is observed due to concentration, and back transfer energy is proposed. The magnetic hysteresis loops display superparamagnetic behavior at 300 K and ferromagnetic ordering at 2 K with a remarkable difference in their magnetization values and confirming the blocking temperatures around physiological temperature ranges. The magneto-luminescence characteristics of the bifunctional system can be easily manipulated under an external magnetic field and suggest an efficient candidate for hybrid medical imaging such as MRI plus X-ray imaging and radiation detection.

Phase Transition Induced Enhanced Performance of Sodium-Rich Na1.2Mn0.8O2–yFy (y = 0–0.5) Cathodes

Increasing capacity and cycle stability is key to successfully commercializing sodium battery technologies. Currently, cation-rich cathodes are well suited for this trend owing to superior overall performance through fluorine substitution in the cation. However, the exact effects and synergy due to fluorine substitution as anions are still unknown. Understanding such synergistic effects can significantly facilitate increasing the capacity, leading to maximum performance at optimum conditions. In this work, the systematic addition of F into sodium-layered oxide and its corresponding changes in the crystal structure or phase formation are extensively studied. More specifically, the effect of fluorine substitution in the anion site on Na diffusion and the Na–Tm polyhedral are extensively studied using X-ray diffraction and subsequent Rietveld analysis. In addition, the effects of F on transition metals (i.e., Mn) and its valence states are also analyzed using X-ray absorption spectroscopy. Na1.2Mn0.8O1.5F0.5 not only showed superior capacity of approximately 172 mAh g–1 and capacity retention but also remarkable cycling stability for up to 300 cycles at higher current densities. Improvements in the performance due to distortion induced by F substitution are also presented. This study provides insight into the transition of cathode material properties from F doping (y = 0–0.2) to F substitution (y ≥ 0.3) and the associated structural changes and capacity improvements.

Enhancement of low-temperature thermoelectric performance via Pb doping in Cu3SbSe4

We investigated the synthesis protocols of the pure and Pb-doped bulk polycrystalline Cu3Sb1-xPbxSe4 (0 ≤ x ≤ 0.04) system and studied their crystallographic and thermoelectric properties intending to reach a high figure of merit (ZT). The solid-state reaction method under a 10−5 Torr vacuum was employed to synthesize the pristine and doped samples. The Rietveld analysis of room-temperature X-ray diffraction confirmed tetragonal structure with space group I4‾2m for all studied compositions. The electrical resistivity [ρ(T)] demonstrated a degenerate semiconducting behavior for pure as well as doped samples. The overall ρ(T) increased with increasing Pb content. The positive values of Seebeck coefficient [S(T)] data in the investigated temperature range for all the studied compositions revealed that holes played a major role in the conduction mechanism. The S(T) values rose with increased temperature, a characteristic of degenerate semiconductors. The temperature-dependent Seebeck coefficient data analysis revealed a narrow bandgap behavior for all studied samples. The analysis suggests that the electronic thermal conductivity only contributed up to 1% to the total thermal conductivity, and the remaining 99% was contributed by lattice thermal conductivity. The estimated ZT values showed as much as 20% enhancement at 380 K for a 1% doped sample, Cu3Sb0.99Pb0.01Se4. The thermoelectric compatibility factor decreased with doping, and a maximum value (1.14 V−1) was found for the pristine sample at 250 K.

Cu2Zn(Sn1−xSix)Se4: Structural Characterization, Vibrational and Physical Properties of CZTSe-Derivatives

Herein, we report the structural characterization and vibrational and physical properties of Cu2ZnSn1−xSixSe4 solid solutions synthesized using the ceramic method. X-ray diffraction analysis and Rietveld analysis of the samples indicated that by increasing the x value from 0 to 0.8, the volume of the unit cell decreased because the ionic radius of silicon is smaller than that of tin. Simultaneously, a phase transition between stannite and wurtz-stannite was observed. The Raman peaks were analyzed by fitting the spectra to identify the vibrational modes by comparison with the experimental data from Cu2ZnSnSe4 and Cu2ZnSiSe4. The spectra of Cu2Zn(Sn1−xSix)Se4 (x = 0.2 and 0.3) show two dominant peaks at approximately 172 and 195 cm−1, which are assigned to the A1 mode of the stannite structure. The optical band gaps for Cu2Zn(Sn0.8Si0.2)Se4 and Cu2Zn(Sn0.2Si0.8)Se4 were 1.30 and 1.74 eV, respectively. These values were intermediate to those of the end members. Electrical properties of Cu2Zn(Sn0.8Si0.2)Se4 revealed p-type conductivity behavior with a carrier concentration of approximately ~+3.50 × 10−19 cm−3 and electrical mobility of 2.64 cm2/V·s.

Tremendous Acceleration of Plant Growth by Applying a New Sunlight Converter Sr4 Al14- x Gax O25 :Mn4+ Breaking Parity Forbidden Transition.

Majority of Mn4+ activated oxide phosphors have the wavelength of excitation and emission suitable for acceleration of plant growth as light converter from sunlight to deep red. Here, it is observed that 60% increase of red emission of Sr4 Al14 O25 :0.01Mn4+ is found by substituting 0.1Ga3+ . It is clarified that the increase is originated from a unique mechanism of breaking parity forbidden transition under the substitution of cation in d-d transition by using the tool of special aberration corrected transmission electron microscope(AC-STEM), pre-edge peak (1s→3d) Mn K-edge X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), Rietveld analysis of X-ray diffraction (XRD) patterns, and reflection spectra. Further, a combination of substituted Ga, Mg, and special double flux H3 BO3 /AlF3 is found to tremendously increase the emission intensity (355% up). Actual growth of chlorella and rose is examined by a combination of the cheap Sr4 Al14 O25 :0.01Mn4+ ,0.007Mg2+ ,0.1Ga3+ and a unique reflection typed phosphor-film system as sunlight converting system. Optical density of chlorella and height of rose grass is increased by 36±14% and 174±80% compared with nonphosphor-film, respectively.

Characterization of Activated Carbon of Rice Husk and Clay Soil Materials for Proton Exchange Membrane of Microbial Fuel Cell

Proton Exchange Membrane (PEM), which can currently work well on Microbial Fuel Cells (MFC), cannot be produced efficiently. This is due to its high cost and properties such as high oxygen diffusion, presence of toxic sulphides, and a potential translucent substrate. Alternatively, clay mixed with activated Carbon will be used to produce PEM. This is because the crystalline clay content has characteristics that are useful in the manufacture of PEM. To produce cheap PEM, this research was conducted to produce rice husk activated Carbon (ACIRH) which was synthesized with sulfuric acid activator solution. In this case, ACIRH is activated by a two-step activation method. The two stages of the activation process were carried out by carbonizing ACIRH at a temperature of 500°C then impregnated with 2M of phosphoric acid solution with a weight ratio of 5:1 for 20 minutes resulting in an ACIRH surface area of 109.885 m2/gram. It was obtained using the method of Brunauer, Emmet, Teller (BET) with an Automated Chemisorption/Physisorption Surface Area Analyzer. ACRH pore size of 96 nm was obtained by applying the method of Density Function Theory (DFT). These results were confirmed by FESEM images showing the porous ACRH mesopore size. Meanwhile, X-Ray Diffraction Test and Rietveld Analysis showed that ACIRH contains 42.3% of Silica and 57.7% of Carbon. While the clay consists of 95.6% of Quartz (SiO2), 1.3% of Annite (KFe3 2+AlSi3O10(OH)2), 1.0% of Portlandite (Ca(OH)2), 0 9% of Brucite (Mg(OH)2), and 1.2% of Rutile (TiO2).

Preparation of PVA/CMC/PVP blended polymer loaded with ZnS1-xCux; investigation of structural and linear/nonlinear optical properties

Nonstoichiometric ZnS1-xCux powders have been loaded to 0.5PVA/0.25CMC/0.25PVP blended polymers using casting method. X-ray diffraction Rietveld analysis was performed for accurate quantification and structural parameters determination of the phases developed in the ZnS1-xCux nanofiller for different content of Cu (x). The surface morphology and chemical composition of the formed polymer blends were investigated using SEM and EDS analysis. The influence of loading the nanofiller with different (x) on the linear and nonlinear optical properties was explored utilizing the UV–vis diffuse reflectance. The variation in the absorption, transmittance, refractive index, extinction coefficient, dielectric constant, energy loss functions, the refractive index dispersion and optical conductivity of the obtained composites was tracked. The determined direct and indirect optical band gap energies of the unloaded blend are 5.16 and 4.92 eV, respectively, which were reduced nonlinearly attaining the lowest values (4.71, 3.5) eV for x = 0.1. The variation in the intensity of fluorescence (FL) and the colors emitted was investigated applying two excitation wavelengths, 317 and 380 nm.

Further Comments on “Engineering Shape Anisotropy of Fe3O4-γ-Fe2O3 Hollow Nanoparticles for Magnetic Hyperthermia”

In their earlier paper, Niraula et al. (ACS Appl. Nano Mater. 2021, 4, 3148–3158) described the morphological, compositional, and magnetic properties of three different magnetite/maghemite or Fe3O4/γ-Fe2O3, hollow nanoparticles, referred to herein as nanorings, short-nanotubes, and long-nanotubes. Scanning electron microscopy indicates that these nanoparticles have lengths of 275 ± 51, 411 ± 92, and 515 ± 98 nm and outer diameters of 201 ± 55, 251 ± 46, and 229 ± 42 nm, respectively, dimensions that are all rather similar in view of their distributions, as is shown in a figure herein. Further, the lengths indicate that these nanoparticles are far larger than what are normally considered nanoparticles. Rietveld refinement of the powder X-ray diffraction patterns presumably reveals the presence of Fe3O4, γ-Fe2O3, and small amounts of α-Fe2O3 in some of the nanoparticles; unfortunately, the lack of refinement details make the validity of these compositions at least problematic. The published iron-57 Mössbauer spectral analysis is marginal. An alternative analysis of both the reported X-ray lattice parameters and the Mössbauer spectral results for the three nanoparticles in terms of solid solutions of magnetite and maghemite, AFe3+[BFe1–3δ2+Fe1+2δ3+□δ]O4, where □ represents a vacancy, δ = 0 corresponds to magnetite, Fe3O4, and δ = 0.333 corresponds to maghemite, γ-Fe2O3, is proposed herein. In the presence of the expected magnetite Verwey transition, the Mössbauer spectral analysis is formulated with the stoichiometry AFe3+[BFe2(1–3δ)2.5+Fe5δ3+□δ]O4, and as far as we can tell, this model is consistent with the Rietveld X-ray diffraction analysis. The values of δ = 0.28(2) and 0.30(1) obtained from the X-ray diffraction and Mössbauer spectral analyses, respectively, indicate that the composition of the nanoparticles is very close to γ-Fe2O3, in contrast to the earlier conclusion. During the course of this reformulation, numerous errors in the mathematical expressions, and in some cases their subsequent misuse, have been discovered and corrected herein whenever possible.

Photoelectrocatalytic CO2 reduction using stable lead-free bimetallic CsAgBr2 halide perovskite nanocrystals

• Rietveld refinement confirming the orthorhombic phase of CsAgBr 2 perovskite nanocrystals with space group Cmcm. • Crystalline nature of the CsAgBr 2 nanocrystals exhibiting photocatalytic CO 2 reduction. • High structural stability displayed by CsAgBr 2 nanocrystals (no degradation up to 6 months) in ambient conditions. • Thermally stable without loss of structural configuration up to 200 °C. • Superior photocatalytic CO 2 reduction with a CO yield ∼14 μmol g −1 h −1 and 50% Faradic efficiency. We report on the fabrication and systematic characterization of highly stable lead-free CsAgBr 2 perovskite nanocrystals (PNC) processed at room temperature without the involvement of any organic ligand. X-ray diffraction (XRD) measurements and Rietveld analysis of the data reveal that the synthesized perovskites are in the orthorhombic phase with space group Cmcm . The optical properties of the CsAgBr 2 PNC are analyzed by UV–Vis absorbance and photoluminescence spectra. Morphological studies are performed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Additionally, the high degree of structural stability of the PNC was reaffirmed by time-dependent XRD profiles, and the thermal stability was studied by Thermogravimetric analysis (TGA). PNC exhibit excellent air stability for up to six months and thermal stability up to 200 °C. Furthermore, we demonstrate superior photoelectrocatalytic CO 2 reduction using CsAgBr 2 PNC with around ∼14 μmol g −1 h −1 of CO yield and 50% Faradic efficiency.

Effect of Fe doping on the lattice structure, microscopic morphology and microwave absorption properties of LaCo1-xFexO3

Perovskite LaCoO3 has unique mixed ionic electronic and structural defects, which has high research value in microwave absorption field. LaCoO3 precursor was prepared by sol-gel method, and LaCo1−xFexO3 (Fe-LCO, x = 0, 0.05, 0.1 and 0.15) with rhombic symmetric structure was successfully synthesized at 600 °C. By refinement of X-ray diffraction (XRD) (Rietveld analysis), it was found that Fe doping makes LaCoO3 lattice constant and cell volume increase. As a dielectric loss microwave absorbing material, the electromagnetic attenuation of LaCoO3 is mainly due to the conduction loss, while the interface and dipole polarization are secondary reasons. It finds that Fe doping can improve the wave absorption performance of LaCoO3. The best absorbing performance was obtained when Fe content is x = 0.1, with the maximum reflection loss of − 38.99 dB at 10.8 GHz and the effective absorption bandwidth (RL<−10 dB) is 4.48 GHz, while the corresponding thickness was only 3 mm. In summary, LaCoO3 has broad application prospects in X and Ku bands.

Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures: The effect of cation migration

Moisture contained in vehicle exhaust gas normally degrades the capacity and efficiency of Pd ion-exchanged zeolites as NOx adsorbents by competitive adsorption on active sites. Here, we report a counterexample to this general proposition, in which moisture facilitates the storage of NO as a nitrosyl complex on hydrated Pd ions in high temperature calcined FER-type zeolites. Divalent Pd2+ cations upon elevated temperature (>800 °C) calcination occupy sterically constrained cationic position in the zeolite framework, and become inactive for the adsorption of probe molecules such as NO. These ‘hidden’ Pd ions, however, are accessible by NO when the zeolite is hydrated, but readily release NO as dehydration proceeds. Combined systematic in situ infra-red data with X-ray diffraction Rietveld analyses reveal that the high temperature-induced relocation of Pd ions to more stable cationic positions located near 6-membered ring of the ferrierite cage is responsible for this behavior.

Influence of oxygen vacancies on the structure and magnetic properties of high entropy (Co,Cr,Fe,Mn,Ni)3O4 ceramics

This research revealed the influence of oxygen vacancies on the structure and magnetic properties of high entropy (Co,Cr,Fe,Mn,Ni)3O4 ceramics. High entropy (Co,Cr,Fe,Mn,Ni)3O4 and (Co,Cr,Fe,Mn,Ni)3O4−n ceramics with a single-phase spinel structure was synthesized by surfactant-assisted hydrothermal technology combined with a heat treatment method. X-ray diffraction Rietveld analysis showed that the lattice constant of (Co,Cr,Fe,Mn,Ni)3O4 and (Co,Cr,Fe,Mn,Ni)3O4−n were 8.346 Å and 8.327 Å, whereas the lattice distortion were 0.314–0.007, respectively. Magnetic studies indicate that all synthesized samples exhibit typical ferrimagnetism at 5–300 K. Compared with (Co,Cr,Fe,Mn,Ni)3O4, the Hc of (Co,Cr,Fe,Mn,Ni)3O4−n increased from 7.99·10 Oe to 9.03·10 Oe, the Ms increased from 4.38 emu·g-1 to 6.59 emu·g-1 at room temperature. The theory calculations reveal that the 3d TM atoms are origin of the magnetism. And compared with (Co,Cr,Fe,Mn,Ni)3O4, the spin density of metal atoms of (Co,Cr,Fe,Mn,Ni)3O4−n increases and the direction change. Our observation and theoretical calculations serve as a link between the defect, structure, and magnetic properties, providing a new sight into understanding the structural origin of the changes in magnetic properties of high entropy ceramics.

Fossil Bioapatites with Extremely High Concentrations of Rare Earth Elements and Yttrium from Deep-Sea Pelagic Sediments

Detailed geochemical and mineralogical insights into some of the richest rare earth elements and yttrium (REY)-containing bioapatites from ocean-floor sediments have been provided by combining laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), electron probe microanalysis (EPMA), Rietveld X-ray diffraction analysis, and Ce L3-edge high energy-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy. Bioapatites at 1.94 and 4.70 m below the seafloor (mbsf) of the Clarion-Clipperton Zone (CCZ) of the Pacific Ocean have 26,600 (RSD = 15.7%, n = 20) and 30,300 (RSD = 14.6%, n = 10) mg/kg (mg/kg) total REY, respectively, and bioapatites at 2.28 and 6.95 mbsf of the Peru Basin have 15,500 (RSD = 15.6%, n = 20) and 15,700 (RSD = 17.8%, n = 29) mg/kg total REY, respectively. All bioapatite specimens have a variety of isomorphic substitutions in all atomic positions of the crystallographic structure. The average crystallochemical formula of bioapatites at 6.95 mbsf of the Peru Basin is [(PO4)2.71(SiO4)0.04(CO3,SO4)0.25][Ca4.57Na0.29Y0.04][F0.87Cl0.21]. All other substituents are below 0.04 atoms per formula unit. HR-XANES provides the first direct evidence for trivalent Ce in sediment apatites. The strong negative geochemical anomaly of Ce in fossil bioapatites is well explained by the occurrence of four valent Ce-MnO2 and CeO2 within the sediment and in seafloor ferromanganese nodules.