Rietveld Analysis Of XRD Data Research Articles

Novel Magnetite (Fe3O4)-Methylcellulose Nanocomposites Synthesized Using the Reverse Co-Precipitation Approach

A simple approach was used to create Fe3O4-methylcellulose (MC) nanocomposites, which were then analyzed using XRD, FTIR, and FE-SEM to determine their structure. The effective factors for enhancing the ratio of magnetite NPs in the samples were investigated using RTFM and optical absorbance. Fe3O4 was synthesized utilizing the reverse co-precipitation technique and magnetic characteristics. Fe3O4/MC nanocomposites with magnetite/MC weight ratios of 0, 0.07, 0.15, and 0.25 have been developed. The diffraction pattern of magnetite is well indexed in accordance with the spinal reference pattern of Fe3O4 (space group: R¯3m), as confirmed by the Rietveld analysis of XRD data of magnetite NPs with an average crystallite size of 50 nm. Magnetite’s insertion into the MC network causes a red shift in the band gap energy (Eg) as the weight percentage of magnetite nanoparticles in the samples rises. The MC, MC-7, MC-15, and MC-25 samples have Eg values of 5.51, 5.05, 2.84, and 2.20 eV, respectively.

Investigation on the structure-optimized magnetic properties of hydrothermally synthesized SrBi2−X(CF)XNb2O9 multiferroic nanocomposites

Hydrothermally synthesized nano multiferroic SrBi2-X(CF)XNb2O9 (SBN-CF), (CF = CoFe2O4 & X = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) composite’s structure correlated magnetic attributes in view of reaction, exchange, and transport of ions have been comprehended from the perspective of electronic sector applications. The produced materials’ phase genesis, morphology, chemical composition, and magnetic characteristics were studied by XRD/Rietveld analysis, FEGSEM/EDS, FTIR, and VSM respectively. The Rietveld analysis of XRD data confirmed a single-phase orthorhombic structure of SBN. Further ferroelectric and cubic spinel structures of the ferrite phase have been noticed from the introduction of CF into the SBN host matrix. The crystallite size as computed (∼23–41 nm) from Debye Scherer’s formula was found to increase with dopant concentration. The imbibed morphological changes necessitated octahedral-shaped grains. The stoichiometric proportion with pronounced absorption bands is evident in EDS and FTIR studies. The impact of CF on SBN was unraveled at room temperature from the VSM study. The saturation magnetization was increased from 0.00 to 3.96 emu g−1, and the obtained coercivity values enhanced from 0.50 to 1400 Oe, due to the random fluctuations of the energy due to domain wall movements, interacting with the defective structure of the SBN material. The stress-induced distortion due to the variation in concentration of CF in SBN was configured from Y-K angles and increased from 33.55° to 61.49°. The high coercivity with a squareness value of less than 0.5 enunciates the genesis of a new class of materials for use in permanent magnet applications and memory devices.

Comprehensive study on the origin of orthorhombic phase stabilization in Gd-doped HfO2 and DFT calculations.

In recent times, ultra-thin films of hafnium oxide (HfO2) have shown ferroelectricity (FE) attributed to the orthorhombic (o) phase of HfO2 with space group Pca21. This polar o-phase could be stabilized in the doped thin film of the oxide. In the present work, both polar and non-polar o-phases of HfO2 could be stabilized in Gd-doped bulk polycrystalline HfO2. Rietveld analysis of XRD data shows that the relative population of o-phases in the presence of the monoclinic (m) phase of HfO2 increases with increasing Gd-content. The local environment around the host atom has been investigated by time differential perturbed angular correlation (TDPAC) spectroscopy, synchrotron based X-ray near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) measurements showed a reduction in grain size with increasing Gd-dopant indicating a solute drag effect. It could be established that the segregation of the Gd-dopant in the grain boundary is a thermodynamically favorable process and the solute drag effect plays an important role in nucleation of the o-phase in bulk HfO2. Stabilization of Gd in both Pbca and Pca21 phases of HfO2 was supported by defect formation energy calculations using density functional theory (DFT). The present study has important implications in future applications of HfO2 in ferroelectric devices and in understanding the role of dopants in stabilizing the o-phase of HfO2 in the bulk.

Molecular dynamic simulations for interactions of oxytetracycline with copper(II)-exchanged NaY zeolite

• Surface structure reflections on interactions of OTC with Cu 2+ -Y was explored. • The Raman spectra revealed ion exchange took place at the 4-ring I site. • Cu 2+ -Y offered reducing strain broadening and narrow particle size distribution. • MD simulation revealed ability of Cu 2+ -Y to attract OTC at force interaction. This study was devoted to examine the effect of the surface structure of Cu 2+ -Y against pure NaY on the photodegradation of oxytetracycline (OTC). The lattice strain examined by Rietveld analysis of XRD data showed strain induced peak broadening at 0.124 for NaY, which diminished to 0.119 for Cu 2+ -Y, prompted by the exchange of Cu 2+ onto the NaY zeolite. Scanning electron microscope (SEM) statistical analysis of Cu 2+ -Y revealed better crystallinity with larger cube width, >2 µm, compared with NaY, 1.7 µm. The vibrational modes and optical properties of Cu 2+ -Y and NaY were compared using Fourier transform infrared (FTIR) spectra, Raman spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). An IR band at 665 cm −1 associated with ν s (Si-O-Cu) was evident for Cu 2+ -Y, which was absent from the spectrum of pure NaY. The Raman bending vibration at 490 cm −1 due to 4-membered ring I in the Cu 2+ -Y displayed a blue shift and a lower value of the full width at half maximum (FWHM) by about 3.02 nm and 0.74 cm −1 , respectively, compared with that of NaY. It was proposed that Cu 2+ ions are attached to shared oxygen of double 4-rings in Y-zeolite. The electronic analysis of Cu 2+ -Y revealed an indirect energy bandgap of 3.17 eV together with an excitonic absorption band at ∼2 eV. The computational molecular adsorption calculations demonstrated the potential effect of Cu 2+ -Y to accommodate five molecules of OTC per unit cell. Molecular dynamics (MD) simulations were committed to support the response behind the higher efficiency and stability of Cu 2+ -Y towards adsorption of the OTC under the force of interaction. OTC molecules brought into being travel toward positions of copper in the optimized OTC@Cu 2+ -Y. In contrast, Na + ions in OTC@NaY held moving towards the edges of the zeolite unit cell and no evidence of the presence of OTC molecules inside the confines of the zeolite cavities. H-bond distribution indicate a close connection and a more stable configuration of OTC inside the Cu 2+ -Y. Thus, MD simulations can safely predict the potential of Cu 2+ to attract the OTC molecules to form OTC@Cu 2+ -Y complexes.

Improved ionic conductivity of Na3+xScxZr2-xSi2PO12 (x = 0.2, 0.3, 0.4, 0.5) NASICON via optimized sintering conditions: Investigation of crystal structure, local atomic structure, and microstructure

We report enhanced Na-ion conductivity of Na3+xScxZr2-xSi2PO12 (x = 0.2–0.5), prepared through solid-state reaction method with optimized sintering temperature of 1220 °C for 15 h. Among four compositions, Na3.4Sc0.4Zr1.6Si2PO12 offers highest total ionic conductivity of 2.6 mS/cm at 25 °C which is much higher than that of parent material. The Rietveld analysis of XRD data reveals a phase mixture of monoclinic and rhombohedral NASICON phases. NMR results indicate local disordering and a fast exchange of Na-ions between the different Na-sites. SEM observation reveals microcrack-free grain boundaries. An understanding of the underlying causes of higher conductivity has been achieved.

Investigation of Multiferroic Properties of Spinel Ferrite (ZnFe2O4) and Ferroelectric (Na0.5Bi0.5TiO3) Composites

The composites of ZnFe2O4 and Na0.5Bi0.5TiO3 were synthesized by solid state reaction route. XRD analysis revealed the formation of two phase system successfully. Rietveld analysis of XRD data confirm that composites having cubic and rhombohedral corresponding to ferrite and ferroelectric phase respectively. The FESEM-EDX studies disclose that average grain sizes are ranges from 0.2 to 0.4 μm. The dielectric constant (ɛ’) and tanδ both shows dispersion at low frequencies and both increases with temperature due to increase in thermally activated hopping. Conductivity curves of each sample follow the universal power law. M–H plots suggest the paramagnetic behavior of these composites.

Dopant driven tunability of dielectric relaxation in MxCo(1-x)Fe2O4 (M: Zn2+, Mn2+, Ni2+) nano-ferrites

Nano-ferrites with tunable dielectric and magnetic properties are highly desirable in modern electronics industries. This work reports the effect of ferromagnetic (Ni), anti-ferromagnetic (Mn), and non-magnetic (Zn) substitution on cobalt-ferrites' dielectric and magnetic properties. The Rietveld analysis of XRD data and the Raman spectroscopic study reveals that all the samples are crystallized in the Fd-3m space group. The T2g Raman mode was observed to split into branches, which is due to the presence of different cations (with different vibrational frequencies) at crystallographic A and B-sites. The magnetization study shows that the MnCoFe2O4 sample has the highest saturation magnetization of 87 emu/g, which is attributed to the presence of Mn2+ cations at the B-site with a magnetic moment of 5 μB. The dielectric permittivity of these nanoparticles (NPs) obeys the modified Debye model, which is further supported by Cole-Cole plots. The dielectric constant of MnCoFe2O4 ferrite is found to be one order higher than that of the other two ferrites. The increased bond length of the Mn2+-O2- bond along with the enhanced d-d electron transition between Mn2+/Co2+⇋Fe3+ cations at the B-site are found to be the main contributing factors for the enhanced dielectric constant of MnCoFe2O4 ferrite. We find evidence of variable-range hopping of localized polarons in these ferrite NPs. The activation energy, hopping range, and density of states NEF, of these polarons were calculated using Motts' 1/4th law. The estimated activation energies of these polarons at 300 K were found to be 288 meV, 426 meV, and 410 meV, respectively, for the MnCoFe2O4, NiCoFe2O4, and ZnCoFe2O4 ferrite NPs, while the hopping range of these polarons were found to be 27.14 Å, 11.66 Å, and 8.17 Å, respectively. Observation of a low dielectric loss of ∼0.04, in the frequency range of 0.1–1 MHz, in these NPs makes them potential candidates for energy harvesting devices in the modern electronics industry.

Synthesis, Structural and Thermal Properties of Layered Perovskites SmBaMn<sub>2</sub>O<sub>5+d</sub> for SOFCs Applications

New layered perovskite oxides with samarium (Sm+3) rare earth doped layered perovskite materials were synthesized and characterised by using X-ray diffraction, scanning electron microscopy (SEM), particle size measurements and thermogravimetric analysis (TGA). Sm0.5Ba0.5MnO3-δ and SmBMn2O5+δ, were synthesized by conventional solid state reaction method. Rietveld analysis of XRD data shows that all materials crystallize in the orthorhombic symmetry in the Pmmm space group. SEM images show porous structures which should be suitable as electrode materials for solid oxide fuel cells (SOFCs). TGA results indicate the mass loss of 0.022% for SmBMn2O5+δ. Density calculation shows the materials have about 85% relative density.

Converting Fe-rich magnetic wastes into active photocatalysts for environmental remediation processes

Abstract Hematite/magnetite photocatalysts were prepared by thermal treatment at 500 and 1000 °C of a Fe-rich waste obtained from a niobium mining. Rietveld analysis of XRD data and 57 Fe Mossbauer spectroscopy indicated that during the heat treatment magnetite is partially converted into hematite, which was the active photocatalytic phase in the samples. The remaining magnetite in the composites was useful to retard the fast electron-hole recombination in hematite. Zeta potential measurements revealed that the point of zero charge (pzc) of the iron oxides increased due to the thermal treatment, which favored the adsorption of negatively charged dye molecules. Diffuse reflectance measurements indicated that the band gap energies of iron oxides increased after the heat treatment due to a higher amount of hematite in those samples. Moreover, the valence band edges of hematite were more positive after the treatment of samples, which increased its dye photo-oxidation power. The photo-oxidation of neat methylene blue and Congo red in the presence of all samples was more efficient than that of neat methyl orange. On the other hand, it was verified from the competitive studies using the three dyes simultaneously that the photo-oxidation of methyl orange was favored, while the methylene blue and Congo red photo-oxidation decreased due to the methyl orange is replacing Congo red in the active photocatalytic sites of hematite. The proposed mechanism of dyes degradation was based on two main processes: (i) direct electron transfer from the dyes to the valence band of hematite, and (ii) dye oxidation by photogenerated OOH radicals on the hematite surface.

Substitutionally driven phase transition and enhanced multiferroic and electrical properties of (1−x) BiFeO3 – (x) Pb(Zr0.52Ti0.48)O3 ceramics (0.0 ≤ x ≤ 1.00)

Polycrystalline samples with compositions 0.0 ≤ x ≤ 1.00 in the (1−x) BiFeO3 – (x) Pb(Zr0.52Ti0.48)O3 system were successfully synthesized by sol-gel method. Rietveld analysis of XRD data confirms the compositional driven phase transition from rhombohedral (R3c) for x = 0.0 to tetragonal (P4mm) for x = 1.0 via intermediate monoclinic phases with Cc and Cm symmetry and co-existence of two ferroelectric phases as well in these ceramics. Remanent magnetization is found to be maximum for x = 0.30 and remanent polarization has increased gradually with x up to x = 1.0. Substantial decrease in dielectric loss and leakage current density has been observed which is due to the suppression of defects like bismuth and oxygen vacancies with increasing x.

Enhanced magnetoelectric properties of BiFeO3 on formation of BiFeO3/SrFe12O19 nanocomposites

Nanocomposites (NCs) comprising (1−x) BiFeO3 (BFO) and x SrFe12O19 (SRF) (x = 0.1, 0.2, 0.3, and 0.4) have been prepared by a sol-gel route. Presence of pure phases of both BiFeO3 (BFO) and SrFe12O19 (SRF) in the NCs for x = 0.3 and 0.4 has been confirmed by Rietveld analysis of XRD data though a minor impurity phase is observed in the case of x = 0.1 and 0.2 NCs. Transmission electron micrographs of the NCs show that particles are mostly spherical with average size of 30 nm. M-H measurements at 300 and 10 K indicate predominantly ferrimagnetic behavior of all the NCs with an increasing trend of saturation magnetization values with increasing content of SRF. Dielectric constant (εr) of the NCs at room temperature shows a dispersive behavior with frequency and attains a constant value at higher frequency. εr − T measurements reveal an increasing trend of dielectric constant of the NCs with increasing temperature and show an anomaly around the antiferromagnetic transition temperature of BFO, which indicates magnetoelectric coupling in the NCs. The variation of capacitance in the presence of magnetic field confirms the enhancement of magnetoelectric effect in the NCs. 57Fe Mössbauer spectroscopy results indicate the presence of only Fe3+ ions in usual crystallographic sites of BFO and SRF.

Polymer‐Templated Mesoporous Li4Ti5O12 as a High‐Rate and Long‐Life Anode Material for Rechargeable Li‐Ion Batteries

AbstractThe synthesis, characterization and Li‐storage properties of cubic mesostructured lithium titanate spinel (Li4Ti5O12) with uniform pores of diameter ≤15 nm and sub‐10 nm grains is reported. The material was prepared in powder form by sol–gel co‐assembly through a soft‐templating method using a poly(isobutylene)‐block‐poly(ethylene oxide) diblock copolymer structure‐directing agent. Electron microscopy demonstrates the mesoporous nature; the BET surface area is around 100 m2 g−1. Rietveld analysis of XRD data and results from XPS, FTIR and Raman spectroscopy indicate a large sensitivity of the phase composition to variations in the heating rate and temperature. Mesoporous Li4Ti5O12 obtained after heating to 600 °C at 10 °C min−1 is virtually single phase, with minor traces of Li2CO3 accumulated on the surface. Half‐cells with a Li metal anode display superior cycling (5 % capacity decay between the fifth and 300th cycles at C/2) and rate performance (>100 mA h g at 10C).

Mechanosynthesis and structural characterization of nanocrystalline Ce1–xYxO2–δ (x=0.1–0.35) solid solutions

A series of nanostructured fluorite-type Ce1–xYxO2–δ (0≤x≤0.35) solid solutions, prepared via high-energy milling of the CeO2/Y2O3 mixtures, are investigated by XRD, HR-TEM, EDS and Raman spectroscopy. For the first time, complementary information on both the long-range and short-range structural features of mechanosynthesized Ce1–xYxO2–δ, obtained by Rietveld analysis of XRD data and Raman spectroscopy, is provided. The lattice parameters of the as-prepared solid solutions decrease with increasing yttrium content. Rietveld refinements of the XRD data reveal increase in microstrains in the host ceria lattice as a consequence of yttrium incorporation. Raman spectra are directly affected by the presence of oxygen vacancies; their existence is evidenced by the presence of vibration modes at ~560 and ~600cm–1. The detailed spectroscopic investigations enable us to separate extrinsic and intrinsic origin of oxygen vacancies. It is demonstrated that mechanosynthesis can be successfully employed in the one-step preparation of nanocrystalline Ce1–xYxO2–δ solid solutions.

The Effect of Basic Oxygen Furnace Slag and Fly Ash Additions in Triaxial Porcelain Composition: Phase and Micro Structural Evolution

Basic oxygen furnace (BOF) slag generated in iron and steel industries were gradually added in a standard triaxial vitrified porcelain tile composition substituting feldspar. Fly ash, a by product of thermal power plant was used as filler by replacing quartz in part or full. The effect of such additions on the physico-mechanical properties of the samples fabricated by ceramic processing technique and heated in the temperature range of 1,050–1,200 °C have been investigated. Out of seven compositions studied, three were selected for detailed investigation on the basis of their lower vitrification temperature. Among three, two have shown early vitrification at 1,150 °C and resulted in highest flexural strength (>70 MPa), while another one vitrified at 1,200 °C and resulted in lower strength (~55 MPa). This variation in mechanical properties is correlated with their densification behaviour, XRD and SEM data. X-Ray diffraction studies confirm the presence of anorthite (CaAl2Si2O8), mullite (Al6Si2O13), fayalite(Fe2SiO4), quartz (SiO2), enstatite(MgSiO3). The weight percentages of crystalline and glassy phases have also been calculated form Rietveld analysis of XRD data. The SEM photomicrographs on selected vitrified specimens supported the XRD observation. The paper also discusses the application of such vitrified products in construction industries.

Structural characterization, electrical and dielectric relaxations in Dy-doped zirconia

Optically active 2mol% dysprosium doped zirconia, Zr0.98Dy0.02O2, was synthesised by conventional solid state route. Rietveld analysis of XRD data of this composition revealed that monoclinic phase dominates at room temperature. SEM micrograph depicted the presence of spherical grains with average grain size of 200nm. The FTIR spectrum of this system indicated a homogeneous distribution of Dy particles among the zirconia structure. The Raman and UV spectra of the system showed various peaks corresponding to different phases present in the system. The electrical conductivity and dielectric properties of this system were measured in temperature range 573–1073K and in the frequency range 20Hz–1MHz. The real part of conductivity spectra was found to follow Jonscher power law. The temperature dependent total conductivity was found to show three different regions, with different activation energy in the entire temperature range. The scaling behaviour of the conductivity spectra also confirms the observed temperature dependence. The temperature and frequency dependence of real part of permittivity and tangent loss indicated the presence of orientational and space charge polarization processes in the system.

Crystallographic and 119Sn and 155Gd Mössbauer analyses of Gd5Ge2(Si1 − xSnx)2 (x = 0.23 and x = 0.40)

We report the structural characterization of Gd5Ge2(Si1 − xSnx)2 (x = 0.23 and x = 0.40) compounds by means of 100 and 298 K-X-ray diffractometry (XRD) and 4 K-155Gd and 298 K-119Sn Mossbauer spectroscopy. These compounds order ferromagnetically at 218.4 and 172.7 K, respectively. At ∼100 K, it was identified the Gd5Si4-orthorhombic phase (type I) for both samples. At ∼298 K, it was identified a Gd5Si2Ge2-monoclinic phase, for x = 0.23 and a Sm5Sn4-orthorhombic phase (type II), for x = 0.40. The Rietveld analysis of XRD data suggests a first order magneto-structural transition at Curie temperature for both compositions. Mossbauer results are well consistent with the proposed crystallographic models for these systems.

Studies on superconducting properties of Zn-doped tetragonal La 1.5Nd 0.5Ca 1Ba 2Cu 5O z system

We present here our studies on Zn-doped La 1.5Nd 0.5Ca 1Ba 2Cu 5O z (La-2125), tetragonal superconductor. Eight different compositions of La 1.5Nd 0.5Ca 1Ba 2(Cu 1− x Zn x ) 5O z ( x=0.00–0.04), were studied through X-ray diffraction, SEM, a.c. susceptibility, resistivity, magnetization measurements and iodometric analysis to explore effects of Zn doping on the structural and superconducting properties. The Rietveld analysis of XRD data shows that all the samples form in tetragonal structure (space group P4/mmm). A.c. susceptibility and resistivity measurements showed that, superconducting transition temperature, T c, is suppressed with increasing Zn in the system at the rate of ∼6–7 K per atomic percent of Zn. The superconducting transition of these materials is found to be highly dependent on dopant concentration. The critical current density J c( H), determined from magnetization measurements, is found to be ∼10 5–10 6 A/cm 2 at low fields. For x=0.01 and 0.015, J c is higher at all fields and is nearly double than that of the pristine La-2125. The enhancement in J c( H) is ascribed to the effective flux line pinning by nonmagnetic Zn at Cu–O planes in this system. For higher concentrations, due to competition between increase of J c arising from pinning by Zn and decrease of J c arising from pair breaking effect of Zn, a cross over is seen in the J c( H) of doped and pristine samples.

Electrochemical and structural characterization of silver hafnium sulfide cathodes

Cubic Ag 4Hf 3S 8 treated with n-butyl lithium was found to function as the cathode in a lithium cell. The structure model of cubic lithiated Ag 4Hf 3S 8 was reconstructed on the basis of Rietveld analysis of XRD data. Its space group was assumed to be identical with that of the source, P4 332 . It was clarified that XRD profiles of lithiated phase can be well explained by the presence of a rigid framework structure of Hf 3S 8 not broken by lithium. Comparative studies on electrochemical lithium insertion into Ag 4Hf 3S 8 were carried out in non-aqueous organic solvents. The electrochemical behavior and structural change of Ag 4Hf 3S 8 cathode were investigated. Effect of electrolytes on discharge behavior was examined for solutions, such as (1) 1 M LiI, (2) 1 M LiClO 4 and (3) 1 M LiPF 6 in propylene carbonate (PC). The initial cell voltage was found to differ with the electrolyte used: 2.4 V for case (1), 2.4 V for case (2) and 3.0 V for case (3).