scholarly journals Synthesis of Samarium OxysulfateSm2O2SO4 in the High-Temperature Oxidation Reaction and Its Structural, Thermal and Luminescent Properties

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1330 ◽  
Author(s):  
Yu. G. Denisenko ◽  
E. I. Sal’nikova ◽  
S. A. Basova ◽  
M. S. Molokeev ◽  
A. S. Krylov ◽  
...  
Keyword(s):  
Structural Model ◽  
Oxidation Process ◽  
Luminescent Properties ◽  
Kinetic Characteristics ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
Temperature Oxidation ◽  
Coordination Environment ◽  
Cell Parameters ◽  
Cation Coordination

The oxidation process of samariumoxysulfide was studied in the temperature range of 500–1000 °C. Our DTA investigation allowed for establishing the main thermodynamic (∆Hºexp = −654.6 kJ/mol) and kinetic characteristics of the process (Ea = 244 kJ/mol, A = 2 × 1010). The enthalpy value of samarium oxysulfate (ΔHºf (Sm2O2SO4(monocl)) = −2294.0 kJ/mol) formation was calculated. The calculated process enthalpy value coincides with the value determined in the experiment. It was established that samarium oxysulfate crystallizes in the monoclinic symmetry class and its crystal structure belongs to space group C2/c with unit cell parameters a = 13.7442 (2), b = 4.20178 (4) and c = 8.16711 (8)Å, β = 107.224 (1)°, V = 450.498 (9)Å3, Z = 4. The main elements of the crystalline structure are obtained and the cation coordination environment is analyzed in detail. Vibrational spectroscopy methods confirmed the structural model adequacy. The Sm2O2SO4luminescence spectra exhibit three main bands easily assignable to the transitions from 4G5/2 state to 6H5/2, 6H7/2, and 6H9/2 multiplets.

scholarly journals Preferred ion diffusion pathways and activation energies for Ag in the crystal structure of stephanite, Ag5SbS4

2009 ◽  
Vol 73 (1) ◽  
pp. 17-26 ◽  
Author(s):  
M. Leitl ◽  
A. Pfitzner ◽  
L. Bindi
Keyword(s):  
Crystal Structure ◽  
Electron Density ◽  
Structural Model ◽  
Careful Analysis ◽  
Type Locality ◽  
Two Dimensional ◽  
Ionic Conductors ◽  
Ion Diffusion ◽  
Unit Cell Parameters ◽  
Cell Parameters

The crystal structure of stephanite fromthe type locality, Freiberg District, Saxony, Germany, was refined in the space group Cmc21, up to a final R index of 0.0427. Unit-cell parameters are: a 7.8329(6) Å, b 12.458(1) Å, c 8.5272(7) Å, V 832.1(1) Å3; Z = 4. The previously reported structural model is confirmed, but a higher-precision refinement was achieved herein by the introduction of thirdorder non-harmonic Gram-Charlier tensors for one Ag atom. In the structure of stephanite, Sb forms isolated SbS3 pyramids, which typically occur in sulphosalts, and Ag occupies sites with coordination ranging fromtriangular to almost tetrahedral. Both the Sb–S and Ag–S bond distances closely match the values commonly observed in the structures of other Ag sulphosalts and sulphides.The use of non-harmonic parameters for Ag allowed a better description of the electron density related to Ag, which is usually difficult to refine in good ionic conductors. A careful analysis of the energy barriers between the Ag sites defines preferred ion-diffusion pathways within the crystal structure of stephanite. The diffusion of Ag ions occurs preferentially along the sites Ag1 and Ag2, giving rise to two-dimensional nets of Ag atoms in which the ion conduction probably takes place.

Triclinic titanite from the Heftetjern granitic pegmatite, Tørdal, southern Norway

2009 ◽  
Vol 73 (5) ◽  
pp. 709-722 ◽  
Author(s):  
A. J. Lussier ◽  
M. A. Cooper ◽  
F. C. Hawthorne ◽  
R. Kristiansen
Keyword(s):  
Short Range ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Granitic Pegmatite ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Cell Parameters ◽  
X Ray Scattering ◽  
Southern Norway

AbstractTwo crystals from a sample of titanite from the Heftetjern granitic pegmatite, Tørdal, southern Norway, were extracted for structure analysis and shown to have triclinic symmetry. Unit-cell parameters are as follows: a = 7.0696(4) Å, b = 8.7167(5) Å, c = 6.5695(3) Å, α = 89.7372(11)°, β = 113.7607(10)°, γ = 90.2929(13)°, V = 370.52(6) Å3 for one crystal and a = 7.0612(5) Å, b = 8.7102(6) Å, c = 6.5628(4) Å, α = 89.7804(16)°, β = 113.7713(13)°, γ = 90.2502(16)°, V = 369.39(7) Å3 for the other. The interaxial angles α and γ deviate from the value of 90° required for monoclinic symmetry by ~200–250 standard deviations. The single-crystal X-ray intensities were averaged in both monoclinic and triclinic Laue symmetries, giving R(merge) values of ~14% and ~1.3% respectively. For both crystals, more than 50 reflections with I > 3σI violated the criterion for the presence of the a-glide required for monoclinic A2/a symmetry. Both crystals were refined in the space group A with Z = 4, and final R1 indices are 4.4% and 4.7% (wR2 = 8.4 and 8.9%) respectively. The composition of one crystal was determined by electron microprobe analysis: Ca[Ti0.623Ta0.105Nb0.018Al0.137Fe0.0463+Sn0.0834+]Σ=1.012(SiO4)O. The characteristic corner-sharing [MO5] chains of identical octahedra observed in monoclinic titanite become chains of alternating M(1) and M(2) octahedra of different size, with the stronger X-ray scattering constituents concentrated at the M(2) site. Short-range bond-valence considerations suggest that the M cations will order as Al—O—Ta in adjacent octahedra, and when present in sufficient amounts, will couple along the chain to break long-range monoclinic symmetry.

Crystal structure of Ca2Zn2(V4O14) and Pb2Cd2(V3O10)(VO4) double vanadates

2018 ◽  
Vol 33 (3) ◽  
pp. 216-224 ◽  
Author(s):  
V. D. Zhuravlev ◽  
A. P. Tyutyunnik ◽  
A. Y. Chufarov ◽  
N. I. Lobachevskaya ◽  
A. A. Velikodnyi
Keyword(s):  
Crystal Structure ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Structural Refinement ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
Conventional Solid State Reaction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

Polycrystalline samples of Ca2Zn2(V4O14) (I) and Pb2Cd2(V3O10)(VO4) (II) were synthesized using the nitrate–citrate method (I) and conventional solid state reaction (II). The structural refinement based on X-ray powder diffraction data showed that the crystal structure of (I) is characterized by monoclinic symmetry with unit-cell parameters a = 6.8044(1) Å, b = 14.4876(3) Å, c = 11.2367(2) Å, β = 99.647(1)° [space group P21/c (No. 14), Z = 4], and the crystal structure of (II) is triclinic with unit-cell parameters a = 7.03813(6) Å, b = 12.9085(1) Å, c = 6.99961(5) Å, α = 90.7265(5)°, β = 96.3789(5)°, γ = 94.9530(6)°, V = 629.470(8) Å3 [space group P$\bar 1$ (No. 2), Z = 2].

An improved structural model for cellulose II

2013 ◽  
Vol 28 (3) ◽  
pp. 194-199 ◽  
Author(s):  
James A. Kaduk ◽  
Thomas N. Blanton
Keyword(s):  
Density Functional ◽  
Structural Model ◽  
Rietveld Method ◽  
Geometry Optimization ◽  
Precise Determination ◽  
Unit Cell ◽  
Cellulose Ii ◽  
Unit Cell Parameters ◽  
Cell Parameters

A sample of cellulose II, prepared by deacetylation of cellulose acetate, has permitted more precise determination of the unit-cell parameters by the Rietveld method. Cellulose II is monoclinic, with space group P21c-axis unique (or P1121) (No. 4) and refined unit-cell parameters a = 8.076(13), b = 9.144(10), c = 10.386(20) Å, γ = 117.00(8)°, and V = 683.5(18) Å3. A density functional geometry optimization using these fixed unit-cell parameters has resulted in an improved structural model for cellulose II. A powder pattern calculated from this new model has been submitted to the ICDD for inclusion in future releases of the Powder Diffraction File.

scholarly journals X-ray powder diffraction analysis of a silver(I) cyclamate complex

2007 ◽  
Vol 22 (1) ◽  
pp. 68-70
Author(s):  
R. Putvinskis ◽  
C. O. Paiva Santos ◽  
M. Cavicchioli ◽  
A. C. Massabni
Keyword(s):  
Powder Diffraction ◽  
Powder Diffraction Data ◽  
Stoichiometric Mixture ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Cell Parameters ◽  
Sodium Cyclamate ◽  
Symmetry Space ◽  
Symmetry Space Group

X-ray powder diffraction data collected for the complex silver(I) cyclamate [Ag(C6H12NO3S)] are reported. This material was obtained from a stoichiometric mixture of sodium cyclamate and AgNO3. The analysis of the data using the Le Bail method showed that the complex has monoclinic symmetry (space group C2/c). The unit cell parameters are a=31.85852(16) Å, b=6.25257(6) Å, c=8.46165(7) Å, and β=95.7651(5)°.

scholarly journals Kegelite: infrared spectroscopy and a structural hypothesis

1991 ◽  
Vol 55 (378) ◽  
pp. 127-134
Author(s):  
R. S. W. Braithwaite
Keyword(s):  
Thermal Analysis ◽  
Infrared Spectroscopy ◽  
Infrared Spectrum ◽  
Structural Model ◽  
Unit Cell ◽  
Chemical Formula ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
A Cell ◽  
Structural Hypothesis

AbstractThe infrared spectrum of kegelite has been measured and is discussed. The infrared spectra of 1 : 1 molar mixtures of leadhillite with pyrophyllite or with muscovite resemble the spectrum of kegelite, the chemical formula of which is a 1 : 1 stoichiometric sum of those of pyrophyllite and of the leadhillite polymorphs. Kegelite is not a physical mixture of these species, but its structure may be an interlayering of phyllosilicate and leadhillite-like structures within the unit cell. The unit cell parameters of pyrophyllite-1Tc and the leadhillite polymorphs are compatible with each other and can be combined to give a cell with parameters close to those of the kegelite cell. A structural model for kegelite on these bases is suggested, which is also consistent with its thermal analysis. The formula of kegelite can be written as Pb8(SO4)2(CO3)4(OH)4(AlOH)4(Si4O10)2.

Synthesis and Crystal Structures of ATi[Nb6Cl18] Compounds (A = K, Rb, Cs, In, Tl)

2000 ◽  
Vol 55 (2) ◽  
pp. 139-144 ◽  
Author(s):  
A. Nägele ◽  
E. Anokhina ◽  
J. Sitar ◽  
H.-J. Meyer ◽  
A. Lachgar
Keyword(s):  
Structure Refinement ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Coordination Environment ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Crystal System ◽  
Rhombohedral Crystal

Abstract New quaternary niobium cluster chlorides corresponding to the general formula ATi[Nb6Cl18] (A = K, Rb, Cs, In, Tl) have been synthesized in sealed quartz tubes at 720 °C, starting from stoichiometric amounts of NbCl5, niobium metal, TiCl3, and ACl (A = K, Rb, Cs), or In or Tl metals. The structures of RbTi[Nb6Cl18] and CsTi[Nb6Cl18] were determined using single­ crystal X-ray diffraction. RbTi[Nb6Cl18] crystallizes in the rhombohedral crystal system, space group R3̄ (no. 148), Z = 3, with lattice parameters: a = 9.163(4), c = 25.014(14) Å (hexagonal setting). The structure refinement converged to R1 = 0.044 and wR2 = 0.058 for all data. In this structure, discrete [Nb6Cl18]4-cluster units are linked by Rb+ and Ti3+ cations, located in a 12-coordinated anticubeoctahedral and octahedral chloride coordination environment, respectively. In contrast, CsTi[Nb6Cl18] crystallizes in the trigonal crystal system, space group P3̄1c (no. 163), Z = 2. The lattice parameters were determined to be a = 9.1075(6), c = 17.0017(8) Å. The structure refinement gives the reliability factors R1 = 0.029 and wR2 = 0.063 for all data. The structure is built up of discrete octahedral [Nb6Cl18]4- cluster units, linked by Cs+ and Ti3+ cations which are located in a distorted hexagonal antiprismatic and octahedral chloride coordination environment, respectively. The structures of the compounds ATi[Nb6Cl18] (A = K, In, Tl) were found to be isotypic with RbTi[Nb6Cl18], and their unit cell parameters were refined using X-ray powder diffraction analysis.

Megawite, CaSnO3: a new perovskite-group mineral from skarns of the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia

2011 ◽  
Vol 75 (5) ◽  
pp. 2563-2572 ◽  
Author(s):  
E. V. Galuskin ◽  
I. O. Galuskina ◽  
V. M. Gazeev ◽  
P. Dzierżanowski ◽  
K. Prusik ◽  
...  
Keyword(s):  
Structural Model ◽  
Contact Metamorphism ◽  
Northern Caucasus ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
Group Mineral ◽  
Cell Parameters ◽  
Ettringite Group ◽  
Electron Back Scattered Diffraction ◽  
Silicate Carbonate

AbstractMegawite is a perovskite-group mineral with an ideal formula CaSnO3 that was discovered in altered silicate-carbonate xenoliths in the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus. Russia. Megawite occurs in ignimbrite, where it forms by contact metamorphism at a temperature >800°C and low pressure. The name megawite honours the British crystallographer Helen Dick Megaw (1907—2002) who did pioneering research on perovskite-group minerals. Megawite is associated with spurrite, reinhardbraunsite, rondorfite, wadalite, srebrodolskite, lakargiite, perovskite, kerimasite. elbrusite-(Zr), periclase, hydroxylellestadite, hydrogrossular, ettringite-group minerals, afwillite. hydrocalumite and brucite. Megawite forms pale yellow or colourless crystals up to 15 urn on edge with pseudo-cubic and pseudo-cuboctahedral habits. The calculated density and average refractive index are 5.06 g cm–3 and 1.89, respectively. Megawite is Zr-rich and usually crystallizes on lakargiite. CaZrO3. The main bands in the Raman spectrum of megawite are at: 159, 183, 262, 283, 355, 443. 474, 557 and 705 cm–1. The unit-cell parameters and space group of megawite, derived from electron back scattered diffraction, are: a = 5.555(3), b = 5.708(2), c = 7.939(5) Å, V = 251.8(1) Å3, Pbnm, Z = 4; they are based on an orthorhombic structural model for the synthetic perovskite CaSn0.6Zr0.4O3.

Obtaining of luminescent material based on NaBaY(BO3)2 doped with terbium and europium ions

2020 ◽  
pp. 10-15
Author(s):  
Zhandos Orazov ◽  
Asset Bolatov ◽  
Nadezhda Kononova ◽  
Vyacheslav Shevchenko ◽  
Konstantin Kokh ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Luminescent Properties ◽  
Luminescent Material ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Trigonal System ◽  
Complex Borate

A new luminescent material based on complex borate NaBaY(BO3)2 doped with Tb3+ and Eu3+ ions was obtained by high-temperature solid-state synthesis. Using X-ray diffraction analysis it was shown that NaBaY(BO3)2:0.07Tb3+:0.1Eu3+ crystallizes in trigonal system with the space group R-3m and isotypic with the mineral buetschliit K2Ca(CO3)2. The crystal structure of the phosphor is layered, formed from [BO3] triangles, [YO6] octahedra, [BaO9] and [NaO9] polyhedra. The calculated unit cell parameters for NaBaY(BO3)2:0.07Tb3+:0.1Eu3+ are: a=5.3510(6) Å, c=17.9338(3) Å, V=444.71(2) Å3. The luminescent properties of NaBaY(BO3)2:0.07Tb3+:0.1Eu3+ were studied.

Oxo-magnesio-hastingsite, NaCa2(Mg2Fe3+3 )(Al2Si6)O22O2, a new anhydrous amphibole from the Deeti volcanic cone, Gregory rift, northern Tanzania

2013 ◽  
Vol 77 (6) ◽  
pp. 2773-2792 ◽  
Author(s):  
A. N. Zaitsev ◽  
E. Yu. Avdontseva ◽  
S. N. Britvin ◽  
A. Demény ◽  
Z. Homonnay ◽  
...  
Keyword(s):  
Chemical Formula ◽  
Unit Cell Parameters ◽  
Monoclinic Symmetry ◽  
Water Determination ◽  
Volcanic Cone ◽  
Cell Parameters ◽  
Northern Tanzania ◽  
Symmetry Space ◽  
Symmetry Space Group ◽  
Measured Density

AbstractOxo-magnesio-hastingsite, ideally NaCa2(Mg2Fe3+3)(Al2Si6)O22O2, is a new anhydrous amphibole from the Deeti volcanic cone in the Gregory rift (northern Tanzania). The mineral occurs as megacrysts up to 12 cm in size in crystal-rich tuff. Oxo-magnesio-hastingsite is brown with a vitreous lustre and has a perfect {110} cleavage. The measured density is 3.19(1) g/cm3. Ferri-kaersutite is biaxial (–), α = 1.706 (2), β = 1.715(2), γ = 1.720(2) (Na light, 589 nm). 2V (calc.) = 73°. Dispersion: r > v, weak; orientation: Y = b; Z ^ c = 8°; pleochroism: strong, Z: dark brown, Y: brown, X: light brown. The average chemical formula of the mineral derived from electron microprobe analyses, Mössbauer spectroscopy and direct water determination is (Na0.67K0.33)Σ1.00(Ca1.87Na0.14Mn0.01)Σ2.02(Mg3.27Fe3+1.25Ti0.44Al0.08)Σ5.04(Al1.80Si6.20O22)(O1.40OH0.60)Σ2.00. It has monoclinic symmetry, space group C2/m and unit-cell parameters a = 9.8837(3), b = 18.0662(6), c = 5.3107(2) Å, b = 105.278(1)o, V = 914.77(5) Å3, Z = 2. The five strongest powder-diffraction lines [d in Å, (I/Io), hkl] are: 3.383 (62) (131), 2.708 (97) (151), 2.555 (100) (), 2.349 (29) () and 2.162 (36) (261). The isotopic composition of H and O, as well as the concentration of trace elements in oxo-magnesio-hastingsite suggest its formation from a melt originated from a mantle source metasomatized by slab-derived fluids.

Sign in / Sign up

Export Citation Format

Share Document