Rietveld Analysis Method Research Articles

Fabrication and the Effects of the Experimental Structure Factor on Barium Titanate Ferroelectric Properties using Polydomain and Landau --- Khalatnikov Models

In this report, powder of barium titanate (BaTiO3) was fabricated using the sol-gel method followed by a sintering process at 900 °C. X-ray diffraction (XRD) was carried out to determine the phase and the crystal structure of the barium titanate. XRD patterns were then refined using the Rietveld analysis method on Fullproof software. The results show the barium titanate (BaTiO3) phase has a tetragonal perovskite structure. EDAX and scanning electron microscope (SEM) were examined to analyze the chemical composition and morphology of the material powder respectively. The results showed that the powder barium titanate (BaTiO3) contains Ba, Ti, and O atoms. The crystallite size is 3 μm and the morphology look homogeneous. The structure factor obtained from the experiment is used to calculate the polarization hysteresis using Polydomain and Landau --- Khalatnikov models. The results of modeling using the structure factor approach using Landau --- Khalatnikov modified model and the Polydomain modified model showed the R-factor (Rwp) is 8.7 and 11.3 %

Pengaruh Suhu Sintering terhadap Pembentukan Senyawa Gd0,95La0,05Ba1,95Sr0,05Cu3O7-?

Research has been conducted variations in sintering temperature between 900 ºC – 950 ºC for 12 hours on the synthesis phase of Gd1Ba2Cu3O7-d substituted La and Sr with stoichiometric composition Gd0,95La0,05Ba1,95Sr0,05Cu3O7-d. This study is intended to find out at what temperature the compound Gd0,95La0,05Ba1,95Sr0,05Cu3O7-d can be formed to the maximum. Samples with composition Gd0,95La0,05Ba1,95Sr0,05Cu3O7-d made from the raw materials Gd2O3, La2O3, BaO, Sr2O3 and CuO. Samples are synthesized using solid-state reaction method by wet mixing with nitric acid (HNO3) as solvent. The sample is sintering in the form of pellets in the furnace without annealing of oxygen gas. The synthesis results were characterized by X-Ray Diffraction (XRD) and analyzed with the Match-3 Program. By using the Entry number 96-153-9606, the results of it analysis showed that sintering temperature had an impact on the formation of phase compounds Gd0,95La0,05Ba1,95Sr0,05Cu3O7-d. Show that the volume fraction is increases with increasing of the sintering temperature, especially from temperatures of 930 ºC to 950 ºC. The highest volume fraction of 75,4263 % was obtained in samples that sintering at 950 ºC. Refinement results with Rietveld analysis method showed phase Gd0,95La0,05Ba1,95Sr0,05Cu3O7-d formed is in orthorhombic symmetry. The volume of cell units is likely to increase as the temperature increases.

Fe-Based Superconductors of ( Ln0.5- xNa0.5+ x)Fe2As2 ( Ln = Ce, Pr).

Recently, we succeeded in synthesizing (La0.5- xNa0.5+ x)Fe2As2 ((La,Na)122) with a solid solution range of 0 ≤ x ≤ 0.35. Superconductivity was induced for 0.15 ≤ x ≤ 0.35, with the highest transition temperature Tc = 27.0 K for x = 0.3. Here, we report the synthesis and physical properties of analogous compounds ( Ln0.5- xNa0.5+ x)Fe2As2 (( Ln,Na)122) ( Ln = Ce, Pr). Samples were synthesized by precisely tuning the reaction temperature according to Ln and x. The solid solution ranges, 0.1 ≤ x ≤ 0.3 ( Ln = Ce) and 0.15 ≤ x ≤ 0.25 ( Ln = Pr), become narrower with increasing atomic number of Ln (which decreases the ionic radius of Ln3+). Bulk superconductivity emerged for 0.2 ≤ x ≤ 0.3 and 0.15 ≤ x ≤ 0.25 with the highest Tc of 25.6 K ( x = 0.3) and 24.7 K ( x = 0.25) for Ln = Ce and Pr, respectively. Crystal structures refined via the Rietveld analysis method showed that the ( Ln,Na)122 compounds ( Ln = La, Ce, Pr) with the highest Tc have almost the same As-Fe-As bond angles (∼107°) and As heights from Fe planes (∼1.43 Å). In addition to the solid solution ranges, the phases in the samples changed depending on the ionic radius of Ln3+. The ( Ln,Na)122 phase competes with the non-superconducting CaFe4As3(143)-type phase of ( Ln,Na)Fe4As3 for Ln = Ce and Pr, whereas only the ( Ln,Na)122 phase was stable for Ln = La. The 143-type phase alone was observed for Ln = Nd, and neither 122- nor 143-type phases were observed for Ln = Sm and Gd.

High-Temperature Neutron Diffraction and Oxide Ion Conduction Path for Pb1-XLa2x/3WO4

Introduction Partially substituting lanthanum ions for lead site of the Scheelite-type structured PbWO4, oxide ion interstitials are formed as Pb1-xLaxWO4+x/2 and high oxide ion conduction appears at high temperature [1]. While most of the oxide ion conductors including zirconias, cerias, or LSGM cause high oxide ion conduction by oxide ion vacancies, the present system utilizes oxide ion interstitials. For the vacancy diffusion, conduction paths can be predicted by connecting regular oxide ions by straight or curved lines. On the other hand, for interstitial diffusion as the present system, conduction path would be complicated. We have conducted high-temperature neutron diffraction on the oxide ion conductor Pb1-xLaxWO4+x/2 (x = 0.2) with oxide ion interstitials to estimate the conduction path by means of the Rietveld analysis and Maximum Entropy Method (MEM) [2]. As a result, two types of oxide ion interstitial sites Oi(1) and Oi(2) were detected. The former can be detected even at room temperature, while the latter appears only at high-temperatures. We have concluded that the oxide ion conduction is performed through the regular oxide ion sites and these two interstitial sites. However, it is still uncertain whether the interstitial site is simply a localized position or surely contributes to the oxide ion conduction. In this study, high-temperature neutron diffraction has been carried out on Pb1-xLa2x/3WO4 (x = 0.1), which has the isostructure with the Pb1-xLaxWO4+x/2 but without apparent interstitials. Comparing the occupancy of the interstitials in these systems, we evaluate the contribution of interstitials to the oxide ion conduction. Experimental Pb1-xLa2x/3WO4 (x = 0.1) sample has been prepared by conventional solid-state reaction method starting from PbO, H2WO4 and La2O3. Before the weighing, La2O3 has been calcined at 900 °C for 6 hours. Stoichiometric mixtures of the starting materials were fired at first at 800 °C in air for 10 hours, finely ground, pressed into pellets under a hydrostatic pressure of 100 MPa for 3 minutes, and finally sintered at 900 °C in air for 10 hours. Crystalline phase of sintered samples was identified by X-ray diffraction measurement. About 10 g of the sample pellets were set in vanadium holder through a thin quartz tube and the neutron powder diffraction experiments were performed in the temperature range between 200 °C and 800 °C by using SHRPD diffractometer in J-PARC. The Rietveld refinements were carried out by using Z-Rietveld code, and the oxide ion conduction path at high temperatures was estimated with Maximum Entropy Method using Z-MEM. Results and Discussions Fig. 1 shows the temperature dependence of the lattice constant obtained by the Rietveld analysis. Both a and c-lengths increase linearly with increasing temperature. The a-length of Pb1-xLa2x/3WO4 is close to that of PbWO4, while Pb1-xLaxWO4+x/2 shows a smaller a-length. On the other hand, c-lengths were not largely varied within all the systems. Fig. 2 shows the temperature dependence of the W-O bond length. In Pb1-xLaxWO4+x/2, it decreases with temperature, whereas it increased in Pb1-xLa2x/3WO4 as PbWO4. In the Pb1-xLaxWO4+x/2 system, it is supposed that WO4 tetrahedra shrink with temperature for the activation of the movement of the oxide ions localized at the interstitial sites. For Pb1-xLa2x/3WO4 system, due to the absence of excess oxide ions, WO4 tetrahedra do not shrink with temperature. Considering the possibility of the oxide ion conduction through the oxide ion interstitials, the Rietveld refinements were carried out on Pb1-xLa2x/3WO4 assuming Oi(1) and Oi(2) of the two types of interstitials as represented in Fig. 3. The refined occupation factor of Oi(1) and Oi(2) for Pb1-xLa2x/3WO4 system are 0.0343 and 0.0129, respectively, while those for Pb1-xLaxWO4+x/2 are 0.0316 and 0.0092, respectively. Since the similar occupation factors are obtained between these two systems even for no apparent interstitial, the deduced oxide ion interstitial position would be attributed to the oxide ion conduction.

Evaluation of austenite volume fraction in TRIP steel sheets using neutron diffraction

The volume fractions of austenite (fA) in hot rolled and heat treated TRIP steel sheets were evaluated using time-of-flight (TOF) neutron diffraction through four different methods. They include the conventional analysis method with random texture assumption, the conventional correction method of (hkl) peak intensities, the Rietveld refinement method using the simply summed spectrum without distinguishing the specimen orientations of all the TOF spectra, and the combined Rietveld analysis method for multiphase textures and constituent phase volume fractions. It was found that for a nearly random TOF spectrum obtained by the simple summation of all the measured TOF neutron spectra, the Rietveld refinement provided a relative satisfactory evaluation precision for fA. Moreover, the precision can be further improved through the simultaneously combined Rietveld analysis method for multiphase textures and constituent phase volume fractions through using all the measured TOF neutron spectra directly. If the texture measurement is unavailable, it is suggested to measure the TOF neutron spectrum through setting the scattering vector along the transverse direction (TD), and to analyze the fA using conventional correction method of (hkl) peak intensities. In addition, together with the microstructure observations and the tensile properties evaluation of these TRIP steels, it was confirmed that the increment of fA evidently improved the combinations of tensile strength and uniform elongation (TS×UEl) of TRIP steels.

Local Structure and in-Situ Average Structure Analysis of LiNi0.8Co0.2O2 Electrode during Charge-Discharge Process By Using Quantum Beam

INTRODUCTION LiCoO2-based materials have been mainly used as a cathode material of the Li ion rechargeable battery. However the Co has some problems, such as high cost and high environmental load. As a candidate of the alternative materials, LiNi0.8Co0.2O2, has drawn much attention because it shows high capacity comparatively, and has an advantage in respect to environmental problem due to low content of Co. The LiNi0.8Co0.2O2 was synthesized for the purpose of reducing cationic mixing and heat stability by substituting a part of Ni of LiNiO2 for Co and was studied. We reported the average structure by using the Rietveld method for neutron and X-ray diffraction patterns in the previous study1).Then we elucidated the local structure of LiNi0.8Co0.2O2 electrode in charge-discharge process by the PDF analysis using neutron and X-ray total scattering methods. The average structure analysis by the in-situ neutron diffraction patterns has been expected. However the measurement and the analytical technique are discussed2). In this research we examined the local structural charge of LiNi0.8Co0.2O2 electrode during charge-discharge process and the Rietveld method for in-situ neutron diffraction pattern of LiNi0.8Co0.2O2. Furthermore, we revealed the average structural change in charge-discharge process of the nonequilibrium state. EXPERIMENTAL LiNi0.8Co0.2O2 was synthesized by mixing Ni-Co precursor with lithium hydroxide hydrate. The precursor was prepared by co-precipitating the aqueous solution of the two metal nitrate salt (Ni, Co) in a stoichiometric ratio of 8:2, with lithium hydroxide. After suction filtration for a few hours, the precipitates were dried at 100°C overnight. The dried material was then mixed with a stoichiometric amount of LiOH-H2O. The mixture was annealed in air at 600 °C for 15 h, and then at 800 °C for 15 h. The product was identified by powder XRD. The composition of lithium and transition metals in the active material was determined by ICP. We analysed the local structure of LiNi0.8Co0.2O2 electrode in charge-discharge process by the PDF analysis using synchrotron X-ray total scattering (BL04B2, SPring-8) and neutron total scattering (BL21, J-PARC). To analyse the average structure of LiNi0.8Co0.2O2 electrode in charge-discharge process in the nonequilibrium state, we also performed the Rietveld method for in-situ neutron diffraction patterns (BL09, J-PARC) by using laminate cell. The cell film was used the PCTFE of the non-hydrogen film and the electrolyte substituted by deuterium. The charge and discharge test were measured at 0.1C. We examined the division time for the integrated in-situ diffraction data in the range of 10 to 40 minutes. Each divided date was analyzed by the Rietveld method using Z-Rietveld. RESULTS AND DISCUSSION We examined the local structure of LiNi0.8Co0.2O2 by PDF analysis using synchrotron X-ray total scattering and neutron total scattering. The Bond Valence Sum(BVS) of Ni and Co, the distortion parameters, λ, σ2 of the MO6(M=Ni, Co) octahedral were calculated from analysed results. It was revealed that the NiO6 octahedra was more distorted than the distortion of CoO6 octahedra. The reason why the distortion was large must cause the Jahn-Teller effect of Ni3+. Then we elucidated the local structure of LiNi0.8Co0.2O2 electrode in 2nd charge-discharge process by the PDF analysis using synchrotron X-ray total scattering method. The distortion parameter of the MO6octahedron came back original state after discharge. It was cearly revealed that there was locally reversible structural changein charge-discharge process. We also examined the method of the analysis for in-situ neutron diffraction data. We compared charge and discharge test using the laminating cell with the electrolyte substituted deuterium or nonsubstituted. In this study we understood there were no change in the electrochemical peroperty by using the electrolyte substituted deuterium. The comparison between the ex-situ and in-situ diffraction data was examined by Rietveld analyses. Furthermore, we examined Rietveld analysis method for neutron diffraction pattern in in-situ measurements. We got the neutron diffraction pattern by dividing the integrated neutron diffraction data in in-situ diffraction data. For example we observed the shift of a peak derived from (101) plane equivalent to the cathode in discharge process. The change of the Li composition and the quantity of cationic mixing in 3a site and 3b site in discharge process was revealed. In addition, no cationic mixing was observed in only discharge process. The technique of the analysis for in-situ neutron diffraction was needed to be further developed. It was performed by help of NEDO (RISING) and shows thanks to the members. References 1) Y. Idemoto, Y. Tsukada, N. Kitamura, A. Hoshikawa and T. Ishigaki, Chem. Lett., 40,168-170 (2011). 2) M. Roberts, et al., J. Power Sources, 226, 249-255 (2013) Figure 1

Neutron diffraction residual stress analysis of Al2O3/Y-TZP ceramic composites

Residual stress measurements were conducted by time-of-flight neutron diffraction and Rietveld analysis method in Al2O3/Y-TZP ceramic composites fabricated by different green processing techniques (a novel tape casting and conventional slip casting) and with different Y-TZP content (5 and 40vol.% Y-TZP). The results show that the residual stresses in Y-TZP particulates are tensile and the ones in Al2O3 matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. As Y-TZP content increased, tension in Y-TZP phase was decreased but compression in Al2O3 matrix was increased (in absolute value). The values of residual stresses for both phases were mainly dependent on the Y-TZP content in the studied Al2O3/Y-TZP composites, irrespective of sample orientation and fabrication processes (a novel tape casting and conventional slip casting).

Structural investigation and hyperfine interactions of BaBixLaxFe12−2xO19 (0.0≤x≤0.5) hexaferrites

Barium hexaferrite, BaFe12O19, substituted by Bi3+ and La3+ (BaBixLaxFe12−2xO19 where 0.0≤x≤0.5) were prepared by solid state synthesis route. The effect of substituted Bi3+ and La3+ ions on the structure, morphology, magnetic and cation distributions of barium hexaferrite were investigated by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR) and Mössbauer spectroscopy. XRD powder patterns were refined by the Rietveld analysis method which confirmed the formation of single phase magneto-plumbite structure and the substitution of La3+ and Bi3+ ions into the lattice of barium ferrite. These results show that both La3+ and Bi3+ ions completely enter into barium hexaferrite lattice without disturbing the hexagonal ferrite structure. The EDX spectra confirmed the presence of all the constituents in expected elemental percentage. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi and La substitutions have been determined. Cation distribution in the presently investigated hexaferrite system was estimated using the relative area of Mössbauer spectroscopy.

Locating Cu in Zeolite SSZ-13 by Synchrotron PXRD Using Maximum Entropy Method

Efficient elimination of environmentally harmful gaseous NOx compounds from automotive diesel emission remains a challenging task. State-of-the-art zeolites with the chabazite framework containing catalytically active Cu2+ (Cu-SSZ-13) have been commercialized as NOx after-treatment catalysts in diesel-powered vehicles, due to its superior activity, selectivity, and durability.[1] However, to meet current and future legislative demands, continuous improvement is of fundamental interest. Prerequisites for an in depth understanding and further improvements, are detailed complete structural models of the Cu-loaded catalyst. This may be achieved by the use of high resolution synchrotron powder X-ray diffraction (PXRD) and iterative Rietveld analysis and Maximum Entropy Method (MEM). Since the content of Cu2+ is low, a protonated system (H-SSZ-13) and model system with monovalent Ag+ ions (Ag-SSZ-13) are also examined. The protonated and dehydrated H-SSZ-13 shows perfectly empty voids, i.e. no water residue or other non-framework species. The H-SSZ-13 structure is used as the initial model for the MEM calculations. For Ag-SSZ-13 MEM analysis clearly pinpoints the Ag+ ion as being located in the 6-ring shifted into the chabazite cage (Figure 1), consistent with the generally accepted site for Ag+ ions in chabazite and reveals the strength of the iterative Rietveld/MEM analysis. For the more challenging case of Cu-SSZ-13 it was still possible through careful analysis and reasoning to locate two separate positions for the Cu2+ in Cu-SSZ-13 (Figure 1). The B site has been suggested by several other studies, but never confirmed experimentally.[2] This is the most complete structural description of zeolite SSZ-13 with stabilizing and catalytically active Cu2+ ions.[3]

Comparison of structural and magnetic properties of La3+ substituted BaFe12O19 prepared by different substitution methods

Effect of La3+ substitution on structural and magnetic properties of Ba1−xLaxFe12O19 (x=0.0–0.2) prepared by two different methods was studied. For the first method, La3+ substituted BaFe12O19 has been directly prepared by solid state synthesis of Fe2O3 and BaCO3 at Fe/Ba molar ratio of 6. For the second method, solid state synthesis of Fe2O3 and Ba1−xLaxFe2O4 at molar composition of 5:1 has been adopted. As-prepared powders were characterized by X-ray diffraction, Mössbauer spectroscopy and vibration sample magnetometry. XRD patterns were refined by the Rietveld analysis method. Single phase barium hexaferrite was obtained by both the methods with a minor amount of residual hematite. Ba1−xLaxFe12O19 prepared from Ba1−xLaxFe2O4 showed higher magnetization (M) which was the maximum for x=0.1, without any remarkable change in the coercivity. The increase in M is attributed to increase in hyperfine field for 12k, 4f1, 4f2, 2a and 2b sites.

Nuclear and charge density distributions in ferroelectric PbTiO3: maximum entropy method analysis of neutron and X-ray diffraction data

We conducted in-situ high-temperature neutron and X-ray diffraction studies on tetragonal PbTiO3. Using a combination of Rietveld analysis and Maximum Entropy Method, the nuclear and charge density distributions were determined as a function of temperature up to 460 °C. The ionic states obtained from charge density distributions reveal that the covalency of Pb–O2 bonds gradually weakens with increasing temperature. The spontaneous polarizations calculated from the contributions of ionic state, ionic displacement, and nuclear polarization, are in good agreement with the experimental measurements. This method provides an effective approach to determine spontaneous polarizations in multiferroics with high-current leakage and low resistance.

Relaxation Analysis of Li-Co-O Cathode Material for Li Ion Secondary Batteries

Li-ion secondary batteries (LIBs) have received much attention as one of the next generation battery system due to its high energy density and operation power, and the research study to improve its performance have been proceeding actively with the recent drastic increase of demands for portable electronic devices and electric vehicle. The research on the crystal phase/ structure of electrode materials is essential to understand the electrode behavior at the lithium insertion/extraction process and to design the advanced high efficiency electrode. The relaxation analysis is important to make the transition of electrode material from kinetic state to equilibrium state clear. We have reported on the relaxation phenomenon of changing their crystal phase/structure after the lithium insertion/extraction process for various electrode materials such as γ-Fe2O3, 1‐3 LiMn2O4, 4‐6 LiFePO4 7 and LiNi1/3Co1/3Mn1/3O2, 8 by using powder X-ray diffraction (XRD) measurement and the Rietveld analysis method. In the previous study on relaxation analysis of γ-Fe2O3 electrode material, it was found that the iron occupancy of 8a sites decreased and that of 16c sites increased with lithium insertion, then the iron occupancy of 8a sites increased and that of 16c sites gradually decreased at the relaxation process after the lithium insertion. It is considered that the lithium preferentially favored the 8a site kinetically, whereas the 16c site is occupied thermodynamically. 1‐3 Recently, we investigated the relaxation phenomenon of LiMn2O4 with the coexistence state of two phases, the Li-rich phase and the Lilean phase, after the lithium insertion by using the Rietveld method, and found that the mole fraction of the Li-rich phase increased and that of the Li-lean phase decreased with the relaxation time. It is considered that, at the lithium insertion process, the Li-lean phase has more vacancies than the Li-rich phase due to lithium deficiency and that the structure of the Li-lean phase was maintained even containing excess lithium in order to promote lithium diffusion. It is considered that the Li-lean phase containing excess lithium formed during the lithium insertion process separated into the Li-lean phase without excess lithium and the Li-rich phase during the relaxation process. 4‐6 LiCoO2 with a layered rock-salt structure is the most widely used cathode material for LIBs due to its excellent reversibility and a high electrochemical potential at the lithium contents x from 1 to 0.5 in terms of LixCoO2. 9‐12 Reimers et al. reported that the phase of LixCoO2 changes as single hexagonal phase for x = 1.00‐0.93, two hexagonal phases for x = 0.93‐0.75, single hexagonal phase for x = 0.75 - near 0.5. 12 In this study, we prepared LixCoO2 samples (x = 0.90, 0.85 and 0.80) at the region of two hexagonal phases coexistence by charging/discharging the cell at the various C rate, then investigated the phase change of the two hexagonal phases with the elapsed time after the lithium extraction/insertion process by using XRD measurement and the Rietveld analysis method.

Spectroscopic properties of Yb3+-doped Y3Al5O12 nano-ceramics obtained under different sintering pressures

Yb3+:YAG nano-ceramics have been obtained by a low temperature/high pressure sintering process. Structural properties have been studied by X-ray diffraction (XRD). Grain sizes and R.M.S micro-strains have been calculated based on the XRD patterns by Rietveld analysis method. Emission spectra and decay curves have been recorded and analyzed. It has been observed that the decay time decreases with the increase of sintering pressure. Presence of Yb3+–Yb3+ pairs have been detected by cooperative emission spectroscopy.

Structural study of a sol-gel derived pyrochlore Bi2Ti2O7 using a Rietveld analysis method based on neutron scattering studies

The crystal structure of the sol-gel derived pyrochlore Bi2Ti2O7 has been refined by a Rietveld analysis method using both neutron scattering and x-ray diffraction data. The sample contains a majority Bi2Ti2O7 phase and minor Bi4Ti3O12, Bi12TiO20, and TiO2 phases. A total goodness of fit from neutron and x-ray scatterings were χ2=2.6, Rp=6.5%, and Rwp=8.6%, which suggest that the refinement is reasonable. The structure of the sol-gel derived pyrochlore Bi2Ti2O7 has been identified as a cubic Fd3¯m with a lattice constant of 10.3735(3) Å and the calculated chemical composition of Bi1.896Ti2O6.884. Furthermore, the measured electrical properties of the sol-gel Bi2Ti2O7 thin film exhibit a ferroelectricity evident from the measured electric field dependent polarization. The observed ferroelectricity of the Bi2Ti2O7 thin film is attributed mainly by Bi atoms occupying 96g site in the unit cell with probability of 0.158 based on the refinement result.

Phase equilibria and crystal structures of solid solutions in the Sr-Fe-Ni-O system at 1100°C in air

The phase equilibria in the Sr-Fe-Ni-O system at 1100°C in air have been studied by x-ray diffraction, and the corresponding phase diagram at constant temperature and pressure has been constructed. The system has been shown to contain two solid-solution series at 1100°C in air: SrFe1 − x Ni x O3 − δ (0 < x ≤ 0.075, sp. gr. Cmmm) and Sr3(Fe1 − y Ni y )2O7 − δ (0 < y ≤ 0.15, sp. gr. I4/mmm). Neither Sr4(Fe1 − z Ni z )6O13 nor Sr(Fe1 − z Ni z )12O19 solid solutions have been identified. The lattice constants and structural parameters of single-phase samples have been refined by the full profile Rietveld analysis method.

A non-invasive analysis of ‘proto-majolica’ pottery from southern Italy by TOF neutrondiffraction

The employment of time-of-flight (TOF) neutron diffraction allowed for the quantitativedetermination of mineral phase contents of the ceramic bulk of several pottery fragmentscoming from Milazzo and Messina (Sicily, southern Italy). From an historical–artistic pointof view, all the samples were dated back to the 12th to 13th centuries AD and classified asbelonging to the ‘proto-majolica’ ceramic class. The adopted procedure is absolutelynon-destructive, so that measurements were performed on the entire fragments without anysampling. The information derived, by applying the Rietveld analysis method, allowed usto formulate hypotheses concerning the fabrication processes of the artefacts.

Crystal Structure Analysis of Si‐ and Zn‐Codoped Tricalcium Phosphate by Neutron Powder Diffraction

Tricalcium phosphate (TCP) is a candidate for a temporary bone implant. Attempts were made to tune the resorption rate of implant for bone reforming by doping different levels of Si and Zn. In this paper, the crystal structure of Si‐ and Zn‐codoped TCP (Si,Zn‐Ca3(PO4)2 (Si,Zn‐TCP)) was studied by using a time‐of‐flight neutron powder diffraction and the Rietveld analysis method. Si,Zn‐TCP was confirmed to have a rhombohedral structure (space group R3c, Z=21), with the unit cell parameters a=b=10.3958(1) Å, c=37.3122(7) Å, α=β=90°, and γ=120° in the hexagonal setting. Of the five cation sites, Ca(1), Ca(2), and Ca(3) positions are still occupied by Ca with minor change in Ca–O bond distance compared with the pure β‐TCP. Whereas the Ca(5) site was totally occupied by Zn. Compared with the original Ca(5)···O distance, the shorter and more uniform Zn(5)···O bond distances show the smaller cation substitution effect and a more ideal octahedral geometry. The site Ca(4) was partially substituted by Zn and Ca,Zn(4)···O(9) bond distance is 2.808(5) Å, much shorter than the original 3.041(1). The Zn substitution content is calculated to be 10% of total Ca sites. A fraction of Si substitutes for P(1) sites and the substitution content is calculated to be 3.9% of total phosphorus sites. The bond valence sums of Ca,Zn(4) is 0.97, higher than 0.67 for Ca(4) in β‐TCP. Other Ca and Zn(5) sites are close to 2.0.

Structure and magnetic properties of ternary potassium lanthanide oxides KLnO2 (Ln = Y, Nd, Sm–Lu)

Crystal structures of ternary potassium lanthanide oxides KLnO2 (Ln=Y, Nd, Sm–Lu) have been determined by powder X-ray diffraction using the Rietveld analysis method. All of the KLnO2 compounds have the same hexagonal α-NaFeO2 structure with space group R3¯m. Magnetic susceptibility measurements for these compounds show paramagnetic behavior down to 1.8K. The specific heat measurements indicate that the Gd, Dy, Ho and Er compounds have a magnetic anomaly at 1.1, 1.8, 1.2 and 0.8K, respectively. The 151Eu Mössbauer spectrum for KEuO2 has been investigated at room temperature.

Ｌｉ二次電池正極活物質ＬｉｘＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２＋δの物性，結晶構造と電極特性のＬｉ組成依存

We investigated the dependence of the properties, crystal structure and electrode characteristics on the Li content of LixCo1/3Ni1/3Mn1/3O2+δ. The crystal structure was determined by Rietveld analysis using neutron diffraction. The electron density images were determined by X-ray diffraction, Rietveld analysis and Maximum Entropy Method. The cycle performance was slightly lower, but the discharge capacity increased at x=1.122. From the crystal structure analysis, the amount of cation mixing was changed by the Li content, that is, a small amount of Ni2+ ions is present in the lithium layers (3a) and extra Li is located in transition metal layer (3b). Ni2+ ions occupied about 4% of the 3a site and Li is located in the 3b site at 0.915≤x≤1.052. On the other hand, Ni2+ ions occupied about 1.2% of the 3a site for x=1.122. In other words, 12% of the total amount of Ni existed in the 3a site at 0.915≤x≤1.052, but, 3.8% of the total amount of Ni existed in the 3a site for x=1.122. The bond length between 3b and 6c (oxygen site) increased with the increasing Li content. From the results, the discharge capacity increased with the decreasing Ni in the 3a site.

Characterization of pottery fragments by nondestructive neutron diffraction

The aim of the present work is the characterization of pottery fragments coming from the town of Caltagirone (Sicily, Italy). The samples belong to very different historical periods, from 18th century B.C. to 16th century A.D., and have finely decorated surfaces. Time-of-flight neutron-diffraction measurements were performed in order to obtain a quantitative identification of the mineralogical composition of the samples. A good determination of the relative weight fractions of the phases was obtained using the Rietveld analysis method. The application of neutron-diffraction technique allowed us to carry out a detailed analysis in a nondestructive way, so intact large fragments were investigated without damaging the precious decoration on the surface.