X-ray Diffraction Rietveld Analysis Research Articles

A comprehensive examination of the local- and long-range structure of Sb6O13 pyrochlore oxide

The crystal structure of the Sb6O13 oxide, exhibiting a defect pyrochlore crystal structure with atomic vacancies, has been studied using a complete set of state-of-the-art techniques. The degree of antimony disproportionation in Sb3+ and Sb5+ valence states has been directly determined around 36% and 64%, respectively, using X-ray absorption near edge structure (XANES). These findings are in excellent agreement with our Rietveld analysis of synchrotron X-ray (SXRD) and neutron powder diffraction (NPD) results. Moreover, the highly distorted Sb3+ coordination due to its lone electron pair has been critically revisited. The bonding distances and coordination of Sb3+ and Sb5+ species closely agree with an extensive dynamic and crystallographic determination using the Extended X-ray Absorption Fine Structure (EXAFS) technique. Most importantly, the specific local disorder of the two distinctive Sb ions has been crosschecked monitoring their unusual Debye–Waller factors.

The Influence of Cu Subtitution on the Crystal and Morphological Structure of Ca<sub>0.9</sub>La<sub>0.05</sub>Bi<sub>0.05</sub>Mn<sub>1-x</sub>Cu<sub>x</sub>O<sub>3</sub> (x = 0, 0.025, 0.05, 0.075, and 0.1) Manganites

The sequence of Cu substituted Ca0.9La0.05Bi0.05Mn1-XCuxO3 ( x = 0, 0.025, 0.05, 0.075, and 0.1) manganite has been studied and it has effect in the structure. The samples was synthesized using the citric acid sol-gel method. The samples was sintered at 800 °C for 5 hours. The crystallography and morphological of all samples was investigated using X-Ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). The Rietveld analysis of the powder x-ray diffraction shows that all the samples crystallize in orthorhombic structure with pnma space group symmetry without any impurity phase. The Cu substitution does not change the crystal structure, but it changes the grain size. SEM results showed a valid different morphological structure. The increasing Cu concentration, it made the grain size larger, dispite all the samples had the same treatment.

Structural Analysis and Theoretical Investigations of the Magnetocaloric Effect for La0.7Ba0.15Ag0.15MnO3 Manganite Prepared Using Sol-Gel Route

Structural analysis, magnetocaloric properties, and theoretical investigations of the magnetocaloric effect were carried out in the crystalline La0.7Ba0.15Ag0.15MnO3 manganite prepared using sol-gel route. The phase purity and structure of this sample were checked by X-ray diffraction technique and Rietveld analysis. From magnetic measurements, the ferromagnetic to paramagnetic (FM-PM) phase transition was observed around TC = 255 K. The maximum change in magnetic entropy (\( \Delta {S}_M^{max} \)) and relative cooling power (RCP) extracted from magnetic measurements were 3.48 J × kg-1 × K-1 and 225 J × kg-1 at an applied magnetic field of 5 T. These magnetocaloric parameters offer to the sample the possible use in the magnetic refrigeration technology. The magnetic entropy simulation by using different theories such as the Weiss molecular mean-field theory and the Landau theory shows good correlation between the theoretical values of −∆SM(T) and the experimental ones estimated from Maxwell relation.

Structural, optical, and electronic properties of non-stoichiometric nano-ZnS1−x: Mnx

Non-stoichiometric ZnS1−x:Mnx nanomaterials were prepared using a thermolysis procedure by decreasing the stoichiometric amount of thiourea relative to the amount of zinc acetate as starting precursors: Zn(Ac)/(1−x) thiourea in the presence of (x) manganese acetate (x = 0, 0.01, 0.03, 0.05, and 0.1). Rietveld X-ray diffraction analysis was used to examine the structural modification in the ZnS lattice induced by sulfur deficiency and Mn2+ incorporation. The samples with x ≤ 0.01 exhibited a single ZnS zincblende phase, while other samples, x ≥ 0.02, have two phases ZnS and ZnO with different percentages. The lattice parameter of the system is governed by the Mn and S amounts in the matrix. A high-resolution transmission electron microscope established the quantum dot nature of the system. Fourier-transform infrared technique confirmed the presence of ZnS and ZnO phases in higher Mn-doped ZnS samples. The bandgap obtained from UV–vis analysis showed non-monotonic dependence on Mn content; it initially decreased and then increased to form a bandgap “bowing.” Photoluminescence analysis revealed that the emission colors depended on the amount of Mn doping in the matrix. The PL intensity raised for all Mn-doped samples as compared with the pristine sample reached its maximum value for the 3% and 5% Mn samples. The PL exhibited a red shift for the high dopant amount of Mn. Density function theory calculation was used to explore the electronic and optical characteristics of pure phases in ZnS1−xMnx system.

Magnetic phase transitions and magnetocaloric effect in ternary rhombohedral Laves phases of Gd2Rh3Ge and Er2Rh3Ge

Magnetic phase transitions in two Mg2Ni3Si-type of Gd2Rh3Ge and Er2Rh3Ge compounds (space group R3‾m, hR18) belonging to rhombohedral Laves phases are studied in this paper. Structural investigations using X-ray diffraction and subsequent Rietveld analysis confirm the rhombohedral R3‾m Laves phase for both compounds. Magnetization as a function of temperature, M(T), identifies the ferromagnetic transition temperature in both samples with TC = 64 K and 20 K for Gd2Rh3Ge and Er2Rh3Ge respectively which is supported by the specific heat, Cp(T). Arrott plots, universal scaling curves by normalizing magnetic entropy changes (ΔSm) and field dependent ΔSm revealed that both compounds undergo second order ferromagnetic phase transitions at TC. Significant magnetocaloric effect (MCE) is observed for both compounds, attaining a value of 12 J kg−1 K−1 at T = 64 K, H = 7 T for Gd2Rh3Ge and 11 J kg−1 K−1 at T = 20 K, H = 7 T for Er2Rh3Ge. The adiabatic temperature change is 5.9 K for Gd2Rh3Ge and 10.5 K for Er2Rh3Ge for H = 7 T.

Correlation between magnetic and electrical properties of La0.7Ba0.15Ag0.15MnO3 manganite prepared by sol gel method

We have reported the solgel synthesis, the structural analysis, and the correlation between magnetic and electrical properties of La0.7Ba0.15Ag0.15MnO3 manganite. The phase purity and structure of this sample were checked by X-ray diffraction technique and Rietveld analysis. M(T) measurement shows a ferromagnetic (FM)-to-paramagnetic (PM) phase transition of second-order type at Curie temperature TC = 255 K. The obtained magnetocaloric parameters offer to the sample the possible use in the magnetic refrigeration technology. The resistivity data, ρ(μ0H, T), show the presence of metal–semiconductor transition and a maximum magnetoresistance (MR) value of the order of 32% at magnetic field of 5 T. The phenomenological percolation model was used to study the conduction mechanism of the sample. It has been also shown that, from analyzing the temperature and magnetic field dependences of the electrical resistivity, it is possible to predict the behavior of the magnetization as well as the change of magnetic entropy near the phase transition temperature. The obtained agreement with experimental data for this analysis is quite reasonable.

Synthesis and Characterization of Lithium Iron Phosphate Carbon Composite (LFP/C) using Magnetite Sand Fe3O4

Lithium Ferro Phosphate Carbon Composite (LFP/C) had been synthesized using solid-state reaction method. Magnetite sand Fe3O4 was used as Fe- source in LFP/C synthesized. Calcination temperature of the sample performed at 400, 500, and 600°C. The phase and composition of samples determined by Rietveld analysis of X-ray diffraction (XRD) pattern. The dominant identified phase at 400°C was diphosphate LiFeP2O7, and the others phases were nasicon Li3Fe2(PO4)3 and hematite Fe2O3. As the temperature getting higher the diphosphate phase LiFeP2O7 transform to nasicon Li3Fe2(PO4)3.The chemical bonds, lattice vibration and other structural features of the sample were investigated using FTIR spectroscopy in range of 1400 – 400 cm-1. Specific vibration modes in LFP-1 to LFP-3 for each bonding were shown by the high intense in certain wavenumber.

Cobalt-Based Multicomponent Oxygen Reduction Reaction Electrocatalysts Generated by Melamine Thermal Pyrolysis with High Performance in an Alkaline Hydrogen/Oxygen Microfuel Cell.

A series of cobalt-based multicomponent electrocatalysts (Co-Cat-T) for the oxygen reduction reaction (ORR) were synthesized by thermal pyrolysis of activated carbon-supported cobalt and melamine mixture from 500 to 800 °C. Their corresponding electrocatalytic performance was systematically investigated toward ORR in an alkaline electrolyte. The electrocatalyst chemical composition and structure evolution (e.g., microstrain, crystallite size, and cell volume) were confirmed by X-ray diffraction Rietveld analyses. The material generated at 550 °C (Co-Cat-T550) showed the largest cell volume of the C3N4 phase with a crystallite size of 4.1 ± 0.1 nm. Independent of the heat-treatment temperature, the cobalt atom was coordinated to nitrogen moieties. The following findings: cobalt inserted in the carbon nitride framework (Co-g-C3N4), abundant Co-Nx and pyridinic-N species, unique encapsulated cross-tubular structure, and disordered carbon domains performed better in the ORR with Co-Cat-T550 among the obtained electrocatalysts. In addition, Co-Cat-T550 showed performance comparable to Pt/C in an alkaline hydrogen/oxygen microfuel cell platform.

Synthesis and Characterization of Lithium Iron Phosphate Carbon Composite (LFP/C) using Magnetite Sand Fe3O4

Lithium Ferro Phosphate Carbon Composite (LFP/C) had been synthesized using solid-state reaction method. Magnetite sand Fe 3 O 4 was used as Fe- source in LFP/C synthesized. Calcination temperature of the sample performed at 400, 500, and 600°C. The phase and composition of samples determined by Rietveld analysis of X-ray diffraction (XRD) pattern. The dominant identified phase at 400°C was diphosphate LiFeP 2 O 7 , and the others phases were nasicon Li 3 Fe 2 (PO 4 ) 3 and hematite Fe 2 O 3 . As the temperature getting higher the diphosphate phase LiFeP 2 O 7 transform to nasicon Li 3 Fe 2 (PO 4 ) 3 .The chemical bonds, lattice vibration and other structural features of the sample were investigated using FTIR spectroscopy in range of 1400 – 400 cm -1 . Specific vibration modes in LFP-1 to LFP-3 for each bonding were shown by the high intense in certain wavenumber.

Investigation on structural, magnetic, dielectric and impedance spectroscopy properties of ‘Gd’ modified multiferroic-ferroelectric solid solutions

A comprehensive study was conducted to analyze the structural, dielectric, impedance spectroscopy and conductivity of Bi0.95Gd0.05FeO3–BaTiO3 (BGF-BT) solid solutions, synthesized via. solid state reaction route. BGF-BT solid solutions show pseudo-cubic structure corroborated by X-ray diffraction patterns and Rietveld analysis. Scanning electron microscopy morphology confirmed that the average grain size decreases with an increase in BT content into BGF. A further insight into the valence chemical states was provided by the core and survey scan of binding energy using the X-ray photoelectron spectroscopy (XPS). The spin-orbit interaction energy in BGF-0.3BT for Fe2p and Bi4f was estimated at 13.3 eV and 5.3 eV respectively. The decrease in oxygen vacancies on incorporation of BT into BGF is also verified after analyzing O 1s core spectra. Raman Spectroscopy also confirmed the chemical bonding and structure of BGF-BT solid solution samples. Maximum magnetization of 1.4047 emu/g was observed for BGF-0.1BT as validated from magnetization hysteresis loops and ferroelectric P vs. E loop measurement confirms the ferroelectric nature of the BGF-BT samples. Analysis of dielectric properties at fixed frequencies confirmed the evidence of magnetoelectric coupling through the broad dielectric anomaly near the reported magnetic transition temperature in BGF-BT samples. The dielectric and impedance spectroscopy studies also confirmed the non-Debye type relaxation phenomenon in the BGF-BT samples. Conductivity measurements followed Jonscher's power law whose experimental fitting determined the pre-factor (A) i.e., polarizability strength and frequency exponent (n). Low activation energy values, 0.187 eV, 0.108 eV and 0.131 eV for BGF-0.1BT, BGF-0.2BT and BGF-0.3BT solid solutions, respectively were observed, show the indication of mobility of defects present in lattice and associated with the hopping conduction mechanism.

Electrochemical Properties and Crystal Structure of Li+/H+ Cation-Exchanged LiNiO2

LiNiO2 has high energy density but easily reacts with moisture in the atmosphere and deteriorates. We performed qualitative and quantitative evaluations of the degraded phase of LiNiO2 and the influence of the structural change on the electrochemical properties of the phase. Li1-xHxNiO2 phase with cation exchange between Li+ and H+ was confirmed by thermogravimetric analysis and Karl Fischer titration measurement. As the H concentration in LiNiO2 increased, the rate capability deteriorated, especially in the low-temperature range and under low state of charge. Experimental and density functional theory (DFT) calculation results suggested that this outcome was due to increased activation energy of Li+ diffusion owing to cation exchange. Rietveld analysis of X-ray diffraction and DFT calculation confirmed that the c lattice parameter and Li-O layer reduced because of the Li+/H+ cation exchange. These results indicate that LiNiO2 modified in the atmosphere has a narrowed Li-O layer, which is the Li diffusion path, and the rate characteristics are degraded.

Analyses of Electric Field-Induced Phase Transformation by Luminescence Study in Eu3+-doped (Na, K)0.5Bi0.5TiO3 Ceramics.

Most analyses of phase transformations detected by rare earth ions are based on the luminescence spectrum, while in this study we focus on the luminescence decay processes. We prepared Eu3+-doped (Na, K)0.5Bi0.5TiO3 ceramics and studied their phase structure before and after poling by luminescence spectra, decay curves, and X-ray diffraction (XRD). Luminescence spectra indicated that electric fields induced a transformation in (Na0.8, K0.2)0.5Bi0.497Eu0.003TiO3 (NKBET20) ceramic from tetragonal to rhombohedral phase (R phase). Based on the decay kinetics and the Judd–Ofelt theory, decay curves were shown to identify the fraction of the transformation quantitatively. The data from decay curves suggest that with electric fields increasing from 0 to 50 kV/cm, the R phase fraction increases from about 23 to 89% and the tetragonal phase (T phase) fraction decreases from about 77 to 11%. XRD Rietveld analyses further confirmed the results. In this work, the analyses of the phase fractions are simplified by the monoexponential decay of the pure phases and the biexponential decay of the mixed phase, showing an easy and inexpensive way of studying the phase structures of the materials.

Synthesis, Structure, and Thermal Stability of Magnesium Oxychloride 5Mg(OH)2∙MgCl2∙8H2O

Today, low-energy and low-carbon footprint alternatives to Portland cement are searched because of huge CO2 emissions coming from Portland clinker calcination. Because of some superior properties of magnesium oxychloride cement (MOC) and the lower carbon footprint of its production, MOC became an intensively studied material with high application potential for the design and development of construction products. In this contribution, magnesium oxychloride with stoichiometry 5Mg(OH)2∙MgCl2∙8H2O (Phase 5) was prepared and characterized. The kinetics of formation and the phase composition of the material were determined using X-ray diffraction and consequent Rietveld analysis. The morphology was studied by scanning electron microscopy, and the chemical composition was determined by both energy-dispersive spectroscopy and X-ray fluorescence. Moreover, the simultaneous thermal analysis in combination with mass spectroscopy and Fourier-transform infrared spectroscopy was employed to study the thermal stability. Using mass spectroscopy, we were able to clarify the mechanism of water and hydrochloric acid release, which was not previously reported. The observed structural and chemical changes induced by exposure of studied samples to elevated temperatures were linked with the measured residual macro and micro parameters, such as bulk density, specific density, porosity, water absorption, compressive strength, and pore size distribution. The Phase 5 revealed a needle-like crystalline morphology which formed rapidly and was almost completed after 96 h, resulting in relatively high material strength. The four-day compressive strength of magnesium oxychloride cement was similar to the 28-day compressive strength of Portland cement. The thermal stability of Phase 5 was low as the observed disruptive thermal processes were completed at temperatures lower than 470 °C.

Formation and stability of C14 type Laves phase in multi component high-entropy alloys

The present investigation reports the formation and stability of multi-component AB2-type Laves phase in Ti–Zr–Ni (V, Cr, Fe, Mn, Co)ternary to octonary alloys system. To probe the formation and stability of AB2-type Laves phase in high-entropy alloys, a series of multi-component alloys have been synthesized via melting under protective Ar atmosphere and subsequent annealing at 525 K for 40 h. Systematic investigation has been carried out to understand phase stability using both thermodynamic and parametric approaches. X-ray diffraction measurement and Rietveld analysis indicate the formation of C14 Laves phase in multi-component alloys. The enthalpy of mixing (ΔHmix), size difference (δ) and valence electron concentrations (VEC) have been found to play stellar role in controlling the formation of multi-component Laves phase in these alloys. The valence electron concentrations and electrons per atom ratio (e/a) dictate the choice of elements for the stabilization of Laves phase in these high-entropy alloys.

Impact of rare earth substitution on structural and optical properties of multiferroic La2−xGdxNiMnO6

Polycrystalline La2−XGdXNiMnO6 (x = 0.0, 0.5 and 1.0) double perovskites were synthesized by auto combustion sol-gel method. The prepared samples have monoclinic phase with space group P21/n, revealed by Rietveld analysis of x-ray diffraction (XRD) pattern. The analysis of reflectivity spectrum showed well resolved infrared (IR) active phonon modes. We discuss the results in terms of different phonon bands originated as a result of atomic vibrations. Optical energy band gap (Eg) has been estimated from optical conductivity (σ1 (ω)) spectrum and UV-visible absorption spectrum. Temperature dependent resistivity measurements suggest variable range hopping conduction mechanism in these multiferroics.

Mechanistic insights and multiple characterizations of cadmium binding to animal-derived biochar

Cattle-derived biochar (CB), which is derived from industrial pyrolysis of cattle carcasses in harmless treatment plants, is a naturally occurring mineral form of carbonate-bearing hydroxyapatite (CHAP) with a small amount of elemental carbon. CB has 4.02% of carbonate content, which falls under the B-type substitution of CHAP. In this work, the Cd(II) sorption capacity of CB was determined to be 0.82 mmol/g, with 97.6% of the Cd(II) uptake contributing to CHAP and only 2.36% of the Cd(II) uptake contributing to the elemental carbon component. The calculation and linear combination fitting (LCF) of Cd L3-edge X-ray absorption near-edge structure (XANES) analysis indicated that the contributions of Cd(II) species to CB presented the following order: ion exchange (57.6%–61.0%) > precipitation (24.4%–29.9%) > surface complexation (12.5%–13.4%). The depth dependent X-ray photoelectron spectroscopy (XPS) showed the presence of ion exchange, which is accompanied by intraparticle diffusion. LCF of XANES and Rietveld analysis of X-ray diffraction (XRD) demonstrated that Cd(II) was precipitated in the form of Cd5H2(PO4)4·4H2O on the CB surface. Furthermore, the precipitate was directly observed and identified by scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Consequently, we revealed the intricate binding mechanism of Cd(II) to CHAP-rich CB and confirmed the importance of surface precipitation.

Improved Electromagnetic Interference Shielding Response of Polyaniline Containing Magnetic Nano-ferrites

Improvement of electromagnetic interference (EMI) shielding materials with miniaturization of devices is an important area of research in various applications like communication, electronic warfare, defense, and different civilian applications. Nano-crystalline ferrite, MFe2O4 (M = Ni, Zn, and Co), powders have been synthesized by sol-gel citrate nitrate precursor method. The crystalline size of samples was found in the range of 20–45 nm as analyzed by XRD and TEM analysis. Polyaniline/ferrite nano-composites with 50 wt% were synthesized by mechanical blending. The structural and magnetic properties of the nano-particles were characterized by using Rietveld analysis of powder X-ray diffraction and vibrating sample magnetometer (VSM) respectively. Using the Rietveld refinement, the goodness of fit, interatomic distance, Bragg contribution, and R factors have been determined. Ferrites and their nano-composites, under applied magnetic field up to 20 KOe, exhibited the hysteresis loops of ferromagnetic nature with maximum saturation magnetization of 51.68 emu/g shown by CoFe2O4. The electromagnetic shielding parameters (various shielding effectiveness and reflection loss) and microwave absorbing properties were measured in X band frequency region (8.2–12.2 GHz). Nano-composites show promising and enhanced EMI shielding behavior with overall highest SE value of 52 dB shown by CoFe2O4 composite.

Introduction of Room Temperature Ferromagnetism in Nanocrystalline Samarium Oxide by Doping of Co-ion

To enhance the magnetic property as well as to get the magnetic ordering in Sm2O3 which is a good dielectric material, Co-ion is substituted by a chemical route. Rietveld analysis of x-ray diffraction (XRD) pattern of the sample (Sm1.90Co0.10O3) suggests that all the dopants are properly substituted in the monoclinic lattice of Sm2O3. XRD analysis and Raman spectroscopic observation ruled out the segregation of Co-cluster or formation of any impurity in Sm1.90Co0.10O3. Magnetic susceptibility ( $$ \chi $$ ) of the sample measured in the range of 300–14 K by Faraday balance indicates the paramagnetic behavior down to 50 K, below which non-linear magnetic nature with ferromagnetic ordering is found. The onset of ferromagnetism in a doped dielectric host is investigated in detail by observing magnetization versus magnetic field (M–H) data and magnetization versus temperature (M–T) curves recorded under zero field cooled and field cooled conditions. All the data extracted from the magnetic measurements are analyzed to yield useful information of the newly developed diluted magnetic dielectric.

Experimental study on autogenous shrinkage behaviors of different Portland blast furnace slag cements

In this study, the differences in autogenous shrinkage behaviors among the Portland blast furnace slag (BFS) cements were investigated experimentally. Portland BFS cements that contain 40–45% BFS were collected from eight different plants in Japan and their autogenous shrinkage at early ages were measured with mortar specimens. After the proper thermal dilation correction of the experimental results, it is indicated that several Portland BFS cements could exhibit significantly different autogenous shrinkage behaviors, even if they are in the same class for the products. The laser diffraction test was conducted to compare fineness of cement particles, but the fineness property of Portland BFS cements was inconsistent with the measured autogenous shrinkages. Subsequently, the chemical composition of each powder and the reaction progress of cement paste specimens were measured by thermal gravimetric analysis and X-ray diffraction Rietveld analysis (XRD). It was realized that the crystallized slag mineral contents through the heat treatment process are consistent with the autogenous shrinkage measurement results and well correlated with hydration level of slag. The crystallized slag mineral contents through the heating process can be an indicator to assess the degree of autogenous shrinkage. The differences in the composition of BFS can be identified through the heat treatment process and this can result in different reaction progresses and autogenous shrinkage behaviors among Portland BFS cements.

Crystal and Electronic Structures of MgCo2−xMnxO4 as Cathode Material for Magnesium Secondary Batteries Using First-Principles Calculations and Quantum Beam Measurements

Abstract The stable structure of the spinels MgCo2O4 and MgCo1.5Mn0.5O4, as Mg secondary battery cathode materials, was investigated by first-principles calculations. The calculated stable structures were compared with the crystal structures obtained by quantum beam measurements. The effect on the electronic structure of the substitution of Mn in MgCo2O4 was examined. Pair distribution function fitting of the normal spinel of MgCo1.5Mn0.5O4 gave a better agreement with experiments than that of MgCo2O4. It was found that Mg/Co cation mixing decreased by the substitution of Mn, as found for the Rietveld analysis of the synchrotron X-ray diffraction. From electron density analysis, it was expected that the Mn-O6 octahedra were more stable than the Co-O6 octahedra because Mn is more attracted to an O atom than a Co atom, that is, the Mn-O bond was stronger than the Co-O bond. The Mg in MgCo1.5Mn0.5O4 was more easily inserted and moved than in MgCo2O4 because the Mg-O bonds near Mn became weak. This fact is consistent with the fact that the first discharge capacity and cycling performance of MgCo1.5Mn0.5O4 were improved over those of MgCo2O4 in charge and discharge tests.