scholarly journals Influence of Dopants on Structure of Polycrystalline Bismuth Niobate

2018 ◽  
Vol 18 (4) ◽  
pp. 35-41
Author(s):  
D. Czekaj ◽  
A. Lisińska-Czekaj
Keyword(s):  
Diffraction Method ◽  
Elementary Cell ◽  
Orthorhombic Symmetry ◽  
Sintering Aids ◽  
X Ray Diffraction ◽  
Bismuth Niobate ◽  
X Ray ◽  
Cell Parameters ◽  
Refinement Method ◽  
Application Potential

Abstract Bismuth niobate (BiNbO4) has attracted attention as a low-fired ceramics with promising microwave application potential. BiNbO4 ceramics was fabricated by mixed oxide method and sintered at temperature T<1000°C. As the sintering aids a small amount of CuO oxide was used. The crystalline structure of the ceramic samples was examined by X-ray diffraction method at room temperature. The Rietveld refinement method was used for analysis of diffraction data. As a result an influence of dopants on crystal structure of bismuth niobate (BiNbO4) ceramics was revealed. It was found that fabricated BiNbO4 ceramics adopted the orthorhombic symmetry (α-BiNbO4 phase, Pnna (52) space group). Small differences in elementary cell parameters were found.

Fabrication of Bi6Fe2Ti3O18 Ceramics by Mixed Oxide Method

2012 ◽  
Vol 730-732 ◽  
pp. 100-104
Author(s):  
Agata Lisińska-Czekaj
Keyword(s):  
Room Temperature ◽  
Ceramic Powder ◽  
Diffraction Method ◽  
Elementary Cell ◽  
X Ray Diffraction ◽  
Stoichiometric Mixture ◽  
Pressing Method ◽  
X Ray ◽  
Cell Parameters ◽  
Ceramic Samples

In the present study Bi6Fe2Ti3O18 (BFTO) ceramics has been fabricated by solid state reaction from the mixture of simple oxides viz. Bi2O3, TiO2 and Fe2O3. Stoichiometric mixture of the powders was thermally analyzed so parameters of the thermal treatment were determined. The EDS measurements have shown conservation of the chemical composition of the ceramic powder after calcination. Hot-pressing method was used for final densification of ceramic samples. The crystalline structure of the sintered samples was examined by X-ray diffraction method at room temperature. It was found that BFTO ceramics sintered at T=980 °C adopted the orthorhombic structure of Aba2 (41) space group with the following elementary cell parameters: a=5.4567(2)Å, b=49.418(2) and c=5.4826(2). Details concerning the atom’s positions are presented.

scholarly journals Bulachite, [Al6(AsO4)3(OH)9(H2O)4]⋅2H2O from Cap Garonne, France: Crystal structure and formation from a higher hydrate

2020 ◽  
Vol 84 (4) ◽  
pp. 608-615
Author(s):  
Ian E. Grey ◽  
Emre Yoruk ◽  
Stéphanie Kodjikian ◽  
Holger Klein ◽  
Catherine Bougerol ◽  
...  
Keyword(s):  
Unit Cell ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Different Temperatures ◽  
Using Data ◽  
Hydrated Aluminium

AbstractBulachite specimens from Cap Garonne, France, comprise two intimately mixed hydrated aluminium arsenate minerals with the same Al:As ratio of 2:1 and with different water contents. The crystal structures of both minerals have been solved using data from low-dose electron diffraction tomography combined with synchrotron powder X-ray diffraction. One of the minerals has the same powder X-ray diffraction pattern (PXRD) as for published bulachite. It has orthorhombic symmetry, space group Pnma with unit-cell parameters a = 15.3994(3), b = 17.6598(3), c = 7.8083(1) Å and Z = 4, with the formula [Al6(AsO4)3(OH)9(H2O)4]⋅2H2O. The second mineral is a higher hydrate with composition [Al6(AsO4)3(OH)9(H2O)4]⋅8H2O. It has the same Pnma space group and unit-cell parameters a = 19.855(4), b = 17.6933(11) and c = 7.7799(5) Å i.e. almost the same b and c parameters but a much larger a parameter. The structures are based on polyhedral layers, parallel to (100), of composition [Al6(AsO4)3(OH)9(H2O)4] and with H-bonded H2O between the layers. The layers contain [001] spiral chains of edge-shared octahedra, decorated with corner connected AsO4 tetrahedra that are the same as in the mineral liskeardite. The spiral chains are joined together by octahedral edge-sharing to form layers parallel to (100). Synchrotron PXRD patterns collected at different temperatures during heating of the specimen show that the higher-hydrate mineral starts transforming to bulachite when heated to 50°C, and the transformation is complete between 75 and 100°C.

X-ray diffraction studies of rapid cooled Al-V and Al-Fe-V alloys

2019 ◽  
Vol 1 (96 extended issue) ◽  
pp. 5-11
Author(s):  
O. Shved ◽  
S. Mudry ◽  
V. Girzhon ◽  
O. Smolyakov
Keyword(s):  
Mechanical Properties ◽  
Physical Properties ◽  
Amorphous Matrix ◽  
Diffraction Method ◽  
Ternary Alloys ◽  
X Ray Diffraction ◽  
Rapid Cooling ◽  
X Ray ◽  
Cell Parameters ◽  
Nonequilibrium Conditions

Purpose: of this paper is to deep and more complete knowledge about the features of phase and structure formation in Al-based alloys with transition metals (TM) Fe and V at rapid cooling from melt. It is known, that nonequilibrium synthesis conditions of such alloys lead to quasicrystalline, amorphous or metastable phases formation, which can significantly improve the physical-chemical properties and first of all the mechanical ones. But understanding of compositional dependences of structure features at formation under nonequilibrium conditions and the correlation of these dependences with physical properties of alloys is far to be clear. Design/methodology/approach: Structure of Al-enriched Al-V, Al-V-Fe rapid cooled alloys was studied by X-ray diffraction method. In order to estimate the influence of structural state of alloy on the mechanical properties the integral microhardness was studied by Vickers method. Findings: Two quasicrystalline icosaedral phases with different cell parameters are revealed in ternary alloys Al100-3xV2xFex (x=2-4). Increasing of transition metal content promotes the formation of phase with higher quasicell parameter embedded in amorphous matrix. With increasing of the transition elements total content from 6 up to 12 at. % the microhardness of alloys increased gradually from 867 to 3050 MPa. Research limitations/implications: Research of nonequilibrium alloys revealed crystalline structure of Al-V alloys and quasicrystalline embedded in amorphous matrix of Al-Fe-V ternary alloys. Obtained results suppose that further structure and physical properties studies of Al-Fe-V alloys will allows to find the conditions to control the producing of materials with desired properties. Practical implications: Using of rapid cooling method for synthesis of Al-enriched Al-Fe-V alloys give an opportunity to produce alloys with significantly improved mechanical properties. Originality/value: Nonequilibrium conditions of cooling allow significantly changes the structure and properties.

scholarly journals Growth and Characterization of Pure and Doped L-Alanine Tartrate Single Crystals

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
K. Rajesh ◽  
B. Milton Boaz ◽  
P. Praveen Kumar
Keyword(s):  
Single Crystals ◽  
Vickers Microhardness ◽  
Diffraction Method ◽  
Dielectric Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Ft Ir ◽  
Ft Ir Spectroscopy

Single crystals of pure and Lanthanum doped L-Alanine Tartrate were grown by slow evaporation method. The cell parameters were determined using single crystal X-ray diffraction method. To improve the physical properties of the LAT crystal, Lanthanum dopant was added by 2 mol%. ICP studies confirm the presence of Lanthanum in the grown LAT crystal. Transparency range of the crystal was determined using UV-VIS-NIR spectrophotometer. The functional groups of pure and doped LAT crystals were analyzed by FT-IR spectroscopy. Using Vickers microhardness tester, mechanical strength of the material was found. Dielectric studies of pure and doped LAT single crystals were carried out. The doped LAT crystal is found to have efficiency higher than that of pure LAT crystal.

Characterization of the adducts of bis(O-isoamyldithiocarbonato) nickel(II) with heterocyclic amines and X-ray structure of bis(O-isoamyldithiocarbonato)-bis(3-bromopyridine)nickel(II)

2016 ◽  
Vol 57 (8) ◽  
pp. 1688
Keyword(s):  
Magnetic Susceptibility ◽  
Spectral Data ◽  
Metal Ion ◽  
Diffraction Method ◽  
Bidentate Ligand ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Infrared Spectral ◽  
Substituted Pyridines

A series of six-coordinated Ni(II) complexes, with the general formula Ni(Xan)L2 (where Xan = isoamyldithiocarbonato and L = 2-bromopyridine, 3-bromopyridine, 4-acetylpyridine, 3-hydroxypyridine and 2-methoxypyridine) are synthesized and characterized by the elemental analysis and various physicochemical techniques such as magnetic susceptibility and conductivity measurements, UV-visible and infrared spectral data. Based on the electronic spectra and magnetic susceptibility measurements, an octahedral geometry is proposed for all the complexes. IR spectral data show that in all these complexes substituted pyridines coordinate to the metal ion through nitrogen atoms occupying the fifth and sixth axial positions, whereas O-alkyldithiocarbonate acts as a monoanion bidentate ligand and occupies the planar positions of octahedral structures. The structure of the adduct with 3-bromopyridine is elucidated by the single crystal X-ray diffraction method. The complex crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.5855(4) Å, b = 9.4984(6) Å, c = 12.4518(8) Å, α = 87.944(5)°, β = 78.843(5)°, γ = 77.794(5)°. The crystal structure of the molecule is stabilized by intermolecular C—H…S and C—H…π interactions.

Schmidite and wildenauerite, two new schoonerite-group minerals from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria

2018 ◽  
Vol 83 (02) ◽  
pp. 181-190
Author(s):  
Ian E. Grey ◽  
Erich Keck ◽  
Anthony R. Kampf ◽  
John D. Cashion ◽  
Colin M. MacRae ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Tetrahedral Site ◽  
Orthorhombic Symmetry ◽  
Charge Balance ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Symmetry Space ◽  
Symmetry Space Group

AbstractSchmidite, Zn(Fe3+0.5Mn2+0.5)2ZnFe3+(PO4)3(OH)3(H2O)8 and wildenauerite, Zn(Fe3+0.5Mn2+0.5)2Mn2+Fe3+(PO4)3(OH)3(H2O)8 are two new oxidised schoonerite-group minerals from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Schmidite occurs as radiating sprays of orange–brown to copper-red laths on and near to altered phosphophyllite in a corroded triphylite nodule, whereas wildenauerite forms dense compacts of red laths, terminating Zn-bearing rockbridgeite. The minerals are biaxial (+) with α = 1.642(2), β = 1.680(1), γ = 1.735(2) and 2Vmeas = 81.4(8)° for schmidite, and with α = 1.659(3), β = 1.687(3), γ = 1.742(3) and 2Vmeas = 73(1)° for wildenauerite. Electron microprobe analyses, with H2O from thermal analysis and FeO/Fe2O3 from Mössbauer spectroscopy, gave FeO 0.4, MgO 0.3, Fe2O3 23.5, MnO 9.0, ZnO 15.5, P2O5 27.6, H2O 23.3, total 99.6 wt.% for schmidite, and FeO 0.7, MgO 0.3, Fe2O3 25.2, MnO 10.7, ZnO 11.5, P2O5 27.2, H2O 24.5, total 100.1 wt.% for wildenauerite. The empirical formulae, scaled to 3 P and with OH– adjusted for charge balance are Zn1.47Mn2+0.98Mg0.05Fe2+0.04Fe3+2.27(PO4)3(OH)2.89(H2O)8.54 for schmidite and Zn1.11Mn2+1.18Mg0.05Fe2+0.08Fe3+2.47(PO4)3(OH)3.25(H2O)9.03 for wildenauerite. The two minerals have orthorhombic symmetry, space group Pmab and Z = 4. The unit-cell parameters from refinement of powder X-ray diffraction data are a = 11.059(1), b = 25.452(1) and c = 6.427(1) Å for schmidite, and a = 11.082(1), b = 25.498(2) and c = 6.436(1) Å for wildenauerite. The crystal structures of schmidite and wildenauerite differ from that of schoonerite in having minor partitioning of Zn from the [5]Zn site to an adjacent vacant tetrahedral site [4]Zn, separated by ~1.0 Å from [5]Zn. The two minerals are distinguished by the cation occupancies in the octahedral M1 to M3 sites. Schmidite has M1 = M2 = (Fe3+0.5Mn2+0.5) and M3 = Zn and wildenauerite has M1 = M2 = (Fe3+0.5Mn2+0.5) and M3 = Mn2+.

scholarly journals Rb-=SUB=-1-x-=/SUB=-Cs-=SUB=-x-=/SUB=-NO-=SUB=-3-=/SUB=- (x=0.025, 0.05, 0.1) монокристаллы и их исследование методом высокотемпературной рентгенографии

2018 ◽  
Vol 52 (6) ◽  
pp. 565
Author(s):  
А.Ф. Хазиева ◽  
В.И. Насиров ◽  
Ю.Г. Асадов ◽  
Ю.И. Алыев ◽  
С.Г. Джабаров ◽  
...  
Keyword(s):  
Melting Point ◽  
Room Temperature ◽  
Diffraction Method ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Transformation Temperatures ◽  
X Ray ◽  
Cell Parameters

AbstractPolymorphic transformations in Rb_0.975Cs_0.025NO_3, Rb_0.950Cs_0.05NO_3, and Rb_0.90Cs_0.1NO_3 crystals grown by us have been studied by the X-ray diffraction method. Four different modifications are found for crystals in the range from room temperature to the melting point. The transformation temperatures and the unit-cell parameters are determined for the crystals of these modifications.

Dehydration of microporous vanadosilicates: the case of VSH-13Na

2018 ◽  
Vol 74 (6) ◽  
pp. 483-491 ◽  
Author(s):  
Rosa Micaela Danisi ◽  
Thomas Armbruster
Keyword(s):  
Structural Similarity ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Extraframework Cations

Microporous VSH-13Na of composition Na2(VO)(Si4O10)·3H2O was synthesized under mild hydrothermal conditions and studied by single-crystal X-ray diffraction at room temperature and 398 K. Its vanadosilicate framework, consisting of sheets of silicate tetrahedra connected by vanadyl-type square-based pyramids, closely resembles that of the mineral cavansite, Ca(VO)(Si4O10)·4H2O. Due to the disorder in the orientation of the short apical vanadyl groups, the topological symmetry of VSH-13Na was originally described in space group Imma. However, when analysing the systematic absences in our dataset, only the 21 screw axis along b was strictly fulfilled suggesting monoclinic space group P1211. The resulting structure in P21 with a = 14.364 (4), b = 9.134 (2), c = 10.373 (3) Å, β = 90.056 (7)°, V = 1360.9 (7) Å3 was interpreted as a case of allotwinning of two polytypes with topologically idealized orthorhombic symmetry: A (∼62%) with antiparallel orientation of the vanadyl groups in adjacent (100) layers and B (∼38%) with all vanadyl groups in adjacent layers oriented in the same way. At 398 K, the structure of VSH-13Na became fully dehydrated and adopted the unit-cell parameters a = 12.584 (16), b = 9.525 (13), c = 9.696 (14) Å, β = 90.10 (4)°, V = 1162 (3) Å3 (space group P21). Release of H2O caused severe contraction of T—O—T angles and the unit-cell volume decreased by ∼15%. Despite their structural similarity, the VSH-13Na framework seems to be more flexible upon dehydration compared with cavansite, whose structure collapsed before removal of the last H2O molecule. Thus, the presence of monovalent or divalent extraframework cations plays a key role in the dehydration process of natural and synthetic vanadosilicates.

scholarly journals Crystallization and preliminary X-ray crystallographic studies of dipeptidyl aminopeptidase BII fromPseudoxanthomonas mexicanaWO24

2014 ◽  
Vol 70 (2) ◽  
pp. 221-224 ◽  
Author(s):  
Yasumitsu Sakamoto ◽  
Yoshiyuki Suzuki ◽  
Ippei Iizuka ◽  
Chika Tateoka ◽  
Saori Roppongi ◽  
...  
Keyword(s):  
Diffraction Method ◽  
Crystal Form ◽  
Diffusion Method ◽  
X Ray Diffraction ◽  
Hanging Drop ◽  
Orthorhombic Crystal ◽  
X Ray ◽  
Cell Parameters ◽  
Multi Wavelength ◽  
Dipeptidyl Aminopeptidase

Dipeptidyl aminopeptidase BII fromPseudoxanthomonas mexicanaWO24 (DAP BII) is able to cleave a variety of dipeptides from the amino-terminus of substrate peptides. For crystallographic studies, DAP BII was overproduced inEscherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data to 2.3 Å resolution were collected using an orthorhombic crystal form belonging to space groupP212121, with unit-cell parametersa= 76.55,b= 130.86,c= 170.87 Å. Structural analysis by the multi-wavelength anomalous diffraction method is in progress.

scholarly journals A new pathway of preparation and refined structure of (NH4)2[FeCl5(H2O)]

2013 ◽  
Vol 6 (1) ◽  
pp. 129-132 ◽  
Author(s):  
Darina Lacková ◽  
Iveta Ondrejkovičová ◽  
Marián Koman
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Structural Parameters ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Hydrolysis Of ◽  
Cl Atoms

Abstract The title compound, (NH4)2[FeCl5H2O] has been prepared by reaction between iron(III) chloride and ammonium chloride which was formed by hydrolysis of isonicotinamide or thionicotinamide in ethanol. The characterization was based on elemental analysis and infrared spectra. The crystal structure of the title compound has been refined by single crystal X-ray diffraction method at 293 K. Crystals are orthorhombic, Pnma, with unit cell parameters: a = 13.760(1) A, b = 9.960(1) A, c = 7.060(1) A, Z = 4 and R = 3.5 %. The iron(III) atom in [FeCl5(H2O)]2- ion is approximately octahedrally coordinated by five Cl atoms and one O atom of H2O molecule. This distortion is caused by the extensively hydrogen-bonded lattice. Structural parameters and IR spectra of similar compounds are compared and discussed.

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