Crystal structure and microstructure of synthetic hexagonal magnesium–cobalt cordierite solid solutions (Mg2−2xCo2xAl4Si5O18)

Co2+-containing cordierite glasses, of nominal compositions (Mg1−xCox)2Al4Si5O18(withx= 0, 0.2, 0.4, 0.6, 0.8 and 1), were prepared by melting colloidal gel precursors. After isothermal heating at 1273 K for around 28 h, a single-phase α-cordierite (high-temperature hexagonal polymorph) was synthesized. All materials were investigated using X-ray powder diffraction and field-emission scanning electron microscopy. The crystal structure and microstructure were determined from X-ray diffraction patterns. Rietveld refinement confirmed the formation of magnesium–cobalt cordierite solid solutions. The unit-cell volume increased with the increase of cobalt content in the starting glass. The crysta…

Microstructural evolution of mullites produced from single-phase gels

The crystalline microstructure of mullites obtained by heating monophasic gels has been investigated. Gels with alumina to silica molar ratio of 3:2 (as in secondary mullite) and 2:1 (as in primary mullite) were prepared by gelling mixtures of aluminium nitrate and tetraethylorthosilicate. Phase transformations were induced by heating the gel precursors, with different final treatment temperatures between 1173 and 1873 K. The mullites formed as a result of thermal treatment were studied by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The crystalline structure (unit-cell parameters) and microstructure were determined from X-ray diffraction pa…

XRD Line Broadening Studies on Mullite

An X-ray diffraction microstructural study on 110, 220, 001 and 111 peaks has been performed on mullite in the temperature range of primary mullite formation in order to monitor nucleation and growth process. Considering the crystallinity of the starting kaolinites, a greater disorder of the kaolinite has been found to enhance the mullite formation. Isothermal growth is related to a decrease in the Al 2 O 3 content of mullite.

X-ray diffraction microstructure analysis of mullite, quartz and corundum in porcelain insulators

Abstract The X-ray diffraction microstructure analysis has been performed on commercial samples of the silica and alumina porcelain insulators obtained at 1300 °C, with the same time of firing. The study was carried out on mullite, corundum and quartz by applying several integral breadth methods (i.e. the Williamson–Hall analysis, the Langford method and the Halder–Wagner approximation) and the Fourier analysis (Warren–Averbach method). The apparent crystallite sizes determined for the mullite are direction-dependent (anisotropic) and within each group of samples, on average, the greatest values are obtained along the direction [0 0 1]. With regard to the microstructure of the corundum and …

A new interpretation and practical aspects of the direct-methods modulus sum function. VIII

Since the first publication of the direct-methods modulus sum function [Rius (1993). Acta Cryst. A49, 406-409], the application of this function to a variety of situations has been shown in a series of seven subsequent papers. In this way, much experience about this function and its practical use has been gained. It is thought by the authors that it is now the right moment to publish a more complete study of this function which also considers most of this practical knowledge. The first part of the study relates, thanks to a new interpretation, this function to other existing phase-refinement functions, while the second shows, with the help of test calculations on a selection of crystal stru…

Quantitative X-ray diffraction phase analysis of airborne particulate collected by a cascade impactor sampler using the Rietveld full-pattern fitting method

Samples of airborne particulate were collected at the “El Ingenio” site in Castellón (Spain) using a cascade impactor sampler. Quantitative analysis of present phases in the aerosol was performed using the full-pattern fitting Rietveld method. Quantitative information was obtained from refined individual scale factors and unit-cell volumes, obtained with a Rietveld refinement program. Quartz, calcite, and gypsum were encountered as major phases, and their size distribution and concentration in the atmosphere were calculated.

XRD microstructural analysis of mullites obtained from kaolinite–alumina mixtures

Abstract A microstructural study of mullite obtained by the reaction sintering of kaolinite–α–alumina mixtures in the range 1150–1700°C has been performed by using X-ray line profile analyses together with scanning and transmission electron microscopy equipped with microanalysis by energy dispersion (SEM-EDS, TEM-AEM). Two kinds of morphology corresponding to primary (elongated grains) and secondary (equiaxed grains) mullite have been observed. A bimodal crystallite size distribution has been detected through XRD microstructural analysis from 1300°C. The results obtained by this method are compared with SEM/TEM data.

Synthesis and crystal structures of two novel triazolopyridine compounds solved by local L.S. minimizations from powder diffraction data

The heteroaryl-substituted triazolopyridines 3-phenyl-7-(pyrazin-2-yl)-[1,2,3]triazolo[1,5-a]pyridine (2) and 3-[6-(pyridazin-3-yl)-pyridin-2-yl]-[1,2,3]triazolo[1,5-a]pyridine (4) have been synthesized and characterized (by HRMS, IR,1H and13C NMR, XRPD, melting point). The crystal structures have been solved from laboratory powder X-ray diffraction data with the direct-space strategy TALP for molecular compounds based on fast local least-squares minimizations. The crystal structure confirmed the formation of the tridentate compound4from a ring chain isomerization process. The almost planar arrangement of atoms in both the structures favors the presence of intermolecularπ–πinteractions, alt…

Synthesis, solution and electrochemical behaviour of new aza-crown ethers derived from biphenyl

Macrocyclic ligands L1–L4 containing biphenyl units have been synthesized. Potentiometric and voltametric studies in the presence and the absence of transition metal cations have been carried out. The relationship between the conformation of the ligand and oxidation states has been also considered. The crystal structure of [HgL2(CN)2]·2Hg(CN)2 has been elucidated by X-ray diffraction techniques.

Bis-cyclic Crown Ether Derived from Biphenyl. Different Behaviour in Complexing Hg(SCN)2 and Hg(CN)2

Abstract A new bis-cyclic crown ether containing a biphenyl unit in its structure has been prepared. This compound shows unexpected behaviour in complexing Hg(CN)2. The new ligand transports this mercury salt across liquid membranes with great efficiency. Clear differences have been observed in the complexation of Hg(CN)2 and Hg(SCN)2. The X-ray structure of a 1:2 mercury complex with Hg(SCN)2 is also reported.

Quantitative X-Ray Powder Diffraction Analysis of Some Feldspars Used as Raw Material in Ceramics

Rietveld Refinement of Tetragonal V4+–ZrO2 Solid Solutions Obtained from Gels by X-ray Powder Diffraction

Abstract The crystal structure of three tetragonal V x Zr 1− x O 2 solid solutions, with x =0.025, 0.05, and 0.075, prepared by heating dried gel precursors at 450°C in air atmosphere, have been determined by Rietveld refinement on the basis of powder X-ray powder diffractometer data. They contain V 4+ cations surrounded by eight oxygens, four at a distance between 2.079 and 2.093 A and another four at longer distances between 2.369 and 2.348 A. The estimation of the crystal average oxygen position from the X-ray lattice parameter of V x Zr 1− x O 2 conform with the relationship proposed by Howard et al. ( J. Am. Ceram. Soc. 81, 241 (1998)).

Crystal structure determination of 1-pentanol from low-temperature powder diffraction data by Patterson search methods

5 pages.-- PACS: 61.66.Hq; 61.50.Lt

Crystal Data for Metal Cimetidine Isotiocionates: M(CM)2(NCS)2 (M = Co(II), Ni(II), Cu(II))

AbstractMetal cimetidine isothiocyanates, M(C10H16SN6)2(NCS)2, where M = Co(II), Ni(II) and Cu(II), have been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined from powder diffractometer data. Refined cell parameters (monoclinic with a primitive cell), powder data, calculated densities and Z value are presented.

Comparative X-ray diffraction study of the crystalline microstructure of tetragonal and monoclinic vanadium–zirconium dioxide solid solutions produced from gel precursors

The microstructural characteristics of solid solutions, prepared by heating dried gel precursors with nominal compositions VxZr1−xO2(0 ≤x≤ 0.1) at 723 and 1573 K, were determined from X-ray diffraction patterns. The crystalline microstructure of the resulting specimens, characterized by a prevalent crystallite shape, a volume-weighted crystallite size distribution and a second-order lattice strain distribution, was found to depend on the vanadium content. A characteristic feature of all size distributions was their bimodality, explained as a result of transformations between tetragonal and monoclinic phases during thermal treatment. A comparative study of the microstructure of both zirconia…

Effect of TiO2 on the mullite formation and mechanical properties of alumina porcelain

Abstract The effect of adding TiO 2 to standard alumina porcelain on its microstructure and flexural strength was investigated. A series of alumina porcelain bodies containing increasing amounts of TiO 2 were prepared by extruding mixtures of raw materials and TiO 2 . Porcelain rods were fired under industrial scheduling in a manufacturing kiln. The overall degree of crystalline and amorphous phase content within the porcelain bodies was quantitatively determined using a Rietveld analysis. Results indicated a higher amount of mullite formation in porcelain bodies containing TiO 2 . Examination of the product materials using field emission scanning electron microscopy showed a high density o…

Copper(II) complexes with the N,N,O-tridentate ligand 6-amino-5-formyl-1,3-dimethyluracilato-(N6)-benzoylhydrazone: synthesis, spectral and XRD studies

Abstract From reactions between different Cu(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H2BEZDO) in alcohol, six new copper complexes with simplified formulas [Cu(HBEZDO)(H2O)(MeOH)]NO3 (1), [CuCl(HBEZDO)(DMF)] (2), [CuBr(HBEZDO)]·2H2O (3), CuBr(HBEZDO) (4), Cu(ClO4)(HBEZDO)·H2O (5), and Cu(SO4)1/2(HBEZDO)·1 1 2 H2O (6) were isolated. The structures of compounds 1, 2 and 3 have been established by means of XRD diffraction methods. In the three compounds, the Schiff base acts as a tridentate monodeprotonated ligand through the N(6), N(51) and O(52) atoms, making two five- and six-membered chelate rings. In the structure of 1 and 2, the solvent molecul…

X-ray powder diffraction phase analysis and thermomechanical properties of silica and alumina porcelains

Chemical and mineralogical characterization, using the Rietveld method, of some silica and alumina rich porcelains and its relationship with thermomechanical properties have been studied in this work. X-ray powder diffraction analysis allows to differ clearly between silica and alumina porcelains. X-ray study shows that both porcelains have a content of vitreous phase. This vitreous phase is higher in the silica than in the alumina porcelain. Dilatometric studies combined with powder diffraction methods shows a strong relationship between silica content and a lower expansion coefficients and between alumina content and a higher crash resistance. Lower contents in vitreous phase in porcelain…

A rietveld study of the cation substitution between uvarovite and yttrium-aluminum synthetic garnets, obtained by sol-gel method

A series of synthetic garnets solid solutions with compositions between Y 3 Al 2 Al 3 O 12 (Y-Al garnet) (YAG) and Ca 3 Cr 2 Si 3 O 12 (uvarovite) was synthesized using the sol-gel method. The expected general formula is (Ca x Y 1-x ) 3 (Cr x Al 1-x ) 2 (Si x Al 1-x ) 3 O 12 where x=0 to x=1. The cation distribution in dodecahedral, octahedral and tetrahedral sites and bond distances in these synthetic garnets were determined using the Rietveld method. It shows the incomplete substitution in small sites. The smaller site the smaller substitution there is

Quantitative Phase Analysis of Mixtures of Three Components using Rietveld and Rius Standardless Methods. Comparative Results

Eight samples, supplied by the Commission on Powder Diffraction of the International Union of Crystallography, through the Round Robin on quantitative phase analysis, were analized using standardless methods. Samples were mixtures of corundum, zincite and fluorite in different ratios. The Rietveld method, using the DBW 3.2 and FULLPROF software, and the Rius method, using MENGE-PC software, were used. Results obtained agree well with the real composition supplied (a posteriori) by the IUCr.

Synthesis and spectral studies on metal complexes with the neutral O,N,O-tridentate Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone

Abstract From the reaction between different Co(II), Cu(II), Zn(II) and Pd(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H 2 BEZDO), in ethanol and acetone media, five complexes with M/L stoichiometry 1/1, containing the neutral organic ligand, have been obtained. These compounds have been studied by IR, 13 C and 1 H-NMR, UV-VIS-NIR and EPR spectroscopies and magnetic measurements. A single crystal X-ray diffraction study has been carried out on the compound [Cu(ClO 4 )(H 2 BEZDO)(H 2 O)]ClO 4 . The structure consists of mononuclear cations [Cu(ClO 4 )(H 2 BEZDO)(H 2 O)] + and uncoordinated perchlorate anions. The coordination environment around the Cu(…

An X-ray powder diffraction study of the microstructural evolution on heating 3:2 and 2:1 mullite single-phase gels

Single-phase gels with compositions 3Al2O3·2SiO2 and 2Al2O3·SiO2 were prepared by gelling mixtures of aluminium nitrate and tetraethylorthosilicate. Gels were fast heated at different temperatures between 900°C and 1600°C. The phase transformation and microstructural changes of both mullite precursor gels over the temperature range were followed by X-ray powder diffraction (XRD), lattice parameter determination (LP), and scanning and transmission electron microscopies (SEM and TEM). The distribution of crystallite sizes and strains were determined by linewidth refinements of X-ray diffraction patterns using the integral breadth method of Langford and the Warren-Averbach analysis. XRD of bot…

Crystal Data for Nickel Cimetidine Chloride: Ni (CM)2 CL2·2H2O

AbstractNickel Cimetidine Chloride, Ni(C10H16SN6)2Cl2·2H2O has been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined by indexing programs, from diffractometer data obtained with copper radiation. A primitive monoclinic cell was found: a = 11.836(3)Å, b = 13.322(5)Å, c = 10.487(2)Å, β = 113.08 (2)°, Z = 2, Dx = 1.462 g/cm3, M.W. = 670.32. These data are consistent with values reported in the literature for other cimetidine complexes.

The crystal structure of 3,5-diisopropyl-4-nitropyrazole from X-ray powder diffraction data

The crystal structure of 3,5-diisopropyl-4-nitropyrazole, 3c, has been determined by a Patterson Search method from laboratory X-ray powder diffraction data. The crystal data are: monoclinic symmetry with the unit-cell parameters aa 19:530O5U; ba 6:485O1U and ca 17:937O3U A; ba 100:32O1U8; space group I2/a ,C 9H15N3O2, Za 8, 293 K. After indexing the powder pattern by two methods, the unit-cell parameters found were refined by a least-squares technique. A whole pattern- fitting program was used to extract the integrated intensities. The structure was solved taking a related compound as a search model and the final Rietveld refinement converged to Rwpa 0.1971 and Rpa 0.1437. The structure pr…

X-Ray Diffraction Analysis of Airborne Particulates Collected by a Cascade Impactor Sampler. Phase Distribution Versus Particle Size

Crystalline microstructure of boehmites studied by multi-peak analysis of powder X-ray diffraction patterns

Nanocrystalline boehmite (gamma-aluminium-oxyhydroxide) is a material of industrial importance, the functionality of which follows from its crystalline microstructure. A procedure for preparing boehmite nanoparticles, comprising the formation of a precipitate by the alkalization of an aqueous solution of aluminium nitrate and subsequent hydrothermal aging, was previously elaborated. The application of an additive (maltitol or tartaric acid) to control the sizes and shapes of crystallites in the produced polycrystalline powder of boehmite was developed. The aim of this work is a study of the effect of the hydrothermal treatment time on nanocrystalline characteristics of boehmite, both in abs…

X-ray powder diffraction study of monoclinic V4+-ZrO2 solid solutions obtained from gels

Abstract Rietveld refinement of six monoclinic V x Zr 1− x O 2 solid solutions, with x =0, 0.01, 0.02, 0.05, 0.075 and 0.1, prepared by heating dried gel precursors at 1300°C in air atmosphere, has been characterized using X-ray powder diffractometer data. The present results confirm that crystal structure of these solid solutions contain V 4+ (Zr 4+ ) cations surrounded by seven oxygens, four at a distance between 2.13 and 2.28 A (referred as to O(2) in the tetrahedrally coordinated oxygens) and other three at a distance between 2.03 and 2.20 A (denoted as O(1) in the triangularly coordinated oxygens). The trends in the lattice parameter variation of V x Zr 1− x O 2 solid solutions specime…

Quantitative x-ray diffraction phase analysis of coarse airborne particulate collected by cascade impactor sampling

Mineralogical composition of Castellon (Spanish Mediterranean coast) atmospheric aerosol was studied by X-ray diffraction by sampling with a cascade impactor without filters. Quantitative phase analysis of natural phases present in the atmospheric coarse aerosol was performed using a modified version of the computer program MENGE, that uses the standardless X-ray method developed by Rius for the quantitative analysis of multiphase mixtures, adapted for PC running. Presence of quartz, calcite and gypsum was identified in the atmospheric aerosol and we have quantified their amounts using the standardless method.

Mechanism of Formation of TiO2-Doped Mullites from Heated Single-Phase Gels Investigated by Structural and Microstructural Parameters

An analysis of the microstructure of TiO 2 -doped mullites prepared from monophasic gels thermally treated in the temperature range 900°-1600°C is reported. Two series of gels with nominal compositions 3(Al 2-x Ti x O 3 ) ·2(SiO 2 ) and 2(Al 2-x Ti x O 3 )·(SiO 2 ), in the range 0≤x≤0.15, were prepared. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to follow the structural and textural evolution from gels to the final doped mullites. The crystallite sizes and microstrains were determined by linewidth refinements of XRD patterns using the integral breadth method of Langford and the Warren-Averbach analysis. XRD patterns showed the formation of Al 2 TiO 5 and…

Solubility and microstructural development of TiO2-containing 3Al2O3·2SiO2 and 2Al2O3·SiO2 mullites obtained from single-phase gels

Abstract The interdependence of the titanium oxide amount and the anisotropic growth of mullites prepared from single-phase gels were investigated. Gels with stoichiometries 3(Al2−xTixO3)·2(SiO2) and 2(Al2−xTixO3)·(SiO2), with 0 ≤ x ≤ 0.15 were prepared by the semialkoxide method. Gels and specimens heated at temperatures between 1200 and 1600 °C were characterized by using infrared spectroscopy (IR), X-ray diffraction (XRD) and transmission and field emission scanning electron microscopies (TEM and FESEM). Al2TiO5 as minor impurity was detected in both series of mullites for gel precursor compositions x = 0.10 and x = 0.15, obtained at temperatures between 1200 and 1600 °C. Variations of l…

Structure Determination from Powder X-Ray Diffraction Data of a Hydrogen-Bonded Molecular Solid with Competing Ferromagnetic and Antiferromagnetic Interactions: The 2-(3,4-Dihydroxyphenyl)-α-Nitronyl Nitroxide Radical

Von den Pulver-Röntgenbeugungsdaten zur Struktur eines Molekülkristalls mit Wasserstoffbrückenbindungen und konkurrierenden ferromagnetischen und antiferromagnetischen Wechselwirkungen – das 2-(3,4-Dihydroxy-phenyl)-α-nitronylnitroxid-Radikal

A tangent formula derived from Patterson-function arguments. VII. Solution of inorganic structures from powder data with accidental overlap

Accidental overlap constitutes one of the principal limitations for the solution of crystal structures from powder diffraction data, since it reduces the number of available intensities for direct-methods application. In this work, the field of application of the direct-methods sum function is extended to cope with powder patterns with relatively large amounts of accidental overlap. This is achieved by refining not only the phases of the structure factors but also the estimated intensities of the severely overlapped peaks during the structure solution process. This procedure has been specifically devised for inorganic compounds with uncertain cell contents and with probable severe atomic di…

Determination of Molecular Crystal Structures from X-Ray Powder Diffraction Data

Synthesis and structural properties of hexaaza[5]helicene containing two [1,2,3]triazolo[1,5-a]pyridine moieties

Abstract We have synthesized a novel hexaaza[5]helicene in a straightforward way from neocuproine. The crystal structure has been elucidated with direct-space strategy TALP which demonstrates the power of the powder X-ray diffraction technique. In this crystal structure it is possible to see an interplanar angle of 33(1)° between the two triazolopyridine rings. The centrosymmetric crystal structure is a racemic mixture, but the resolution was not possible due to a ring-chain isomerization in a solution that produces a dynamic racemization.