scholarly journals The Formation of Cr-Al Spinel under a Reductive Atmosphere

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3218
Author(s):  
Oleksandr Shtyka ◽  
Waldemar Maniukiewicz ◽  
Radoslaw Ciesielski ◽  
Adam Kedziora ◽  
Viktar Shatsila ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transformations ◽  
Unit Cell Parameter ◽  
Spinel Structure ◽  
Cell Parameter ◽  
Ambient Conditions ◽  
Cubic Crystal ◽  
Reductive Atmosphere ◽  
Α Al2o3 ◽  
First Time

In the present work, for the first time, the possibility of formation of CrAl2O4 was shown from the equimolar mixture of co-precipitated Al2O3 and Cr2O3 oxides under a reductive environment. The crystallographic properties of the formed compound were calculated using the DICVOL procedure. It was determined that it has a cubic crystal structure with space group Fd-3m and a unit cell parameter equal to 8.22(3) Å. The formed CrAl2O4 is not stable under ambient conditions and easily undergoes oxidation to α-Al2O3 and α-Cr2O3. The overall sequence of the phase transformations of co-precipitated oxides leading to the formation of spinel structure is proposed.

scholarly journals Кристаллическая структура и ширина запрещенной зоны твердых растворов (MnIn-=SUB=-2-=/SUB=-S-=SUB=-4-=/SUB=-)-=SUB=-1-x-=/SUB=-·(AgIn-=SUB=-5-=/SUB=-S-=SUB=-8-=/SUB=-)-=SUB=-x-=/SUB=-

2018 ◽  
Vol 52 (8) ◽  
pp. 958
Author(s):  
И.В. Боднарь ◽  
Чан Бинь Тхан
Keyword(s):  
Crystal Structure ◽  
Band Gap ◽  
Single Crystals ◽  
Absorption Edge ◽  
Entire Range ◽  
Spinel Structure ◽  
Cell Parameter ◽  
Fundamental Absorption Edge ◽  
Composition Parameter ◽  
First Time

AbstractThe (MnIn_2S_4)_1– x • (AgIn_5S_8)_ x alloy single crystals are grown for the first time by the Bridgman method in the entire range of component concentrations. The composition of the single crystals and their crystal structure are determined. It is shown that the alloy crystallizes in the cubic spinel structure. The unit-cell parameter of the single crystals ( a ) is calculated, and its dependence on the composition parameter ( x ) is determined. It is established that the parameter a linearly varies with x . From the transmittance spectra in the region of the fundamental absorption edge, the band gap ( E _ g ) of the MnIn_2S_4 and AgIn_5S_8 compounds and (MnIn_2S_4)_1– x • (AgIn_5S_8)_ x alloys is determined, and the dependence of Eg on the parameter x is constructed. It is found that the band gap E _ g nonlinearly varies with x and has a maximum at x = 0.6.

Natrophosphate from the Ilímaussaq alkaline complex, South Greenland

2001 ◽  
pp. 139-141
Author(s):  
Ole V. Petersen ◽  
Alexander P. Khomyakov ◽  
Henning Sørensen
Keyword(s):  
Refractive Index ◽  
Kola Peninsula ◽  
Unit Cell Parameter ◽  
Cell Parameter ◽  
Water Soluble ◽  
Type Locality ◽  
Drill Core ◽  
Alkaline Complex ◽  
First Time ◽  
Alkaline Complexes

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Petersen, O. V., Khomyakov, A. P., & Henning. (2001). Natrophosphate from the Ilímaussaq alkaline complex, South Greenland. Geology of Greenland Survey Bulletin, 190, 139-141. https://doi.org/10.34194/ggub.v190.5184 _______________ The rare mineral natrophosphate has been identified for the first time in the Ilímaussaq alkaline complex in a drill core from the Kvanefjeld area. It occurs sparsely in zoned veinlets with cores of natrophosphate and borders of fibrous trona. The natrophosphate is more or less smoky, transparent and unaltered. The refractive index n = 1.448 ± 0.005 is low compared to that given for the material from the type locality, Khibina alkaline complex, Kola Peninsula; the unit cell parameter a = 27.76 ± 0.05 Å is in excellent agreement with that given for the material from the type locality. The veins occur in hyper-agpaitic naujakasite lujavrite; villiaumite is an associated mineral. Only a few water-soluble minerals have so far been found in the Ilímaussaq alkaline complex compared to the wealth of such minerals in the Khibina and Lovozero alkaline complexes. This is possibly at least partly due to lack of necessary precautions during sampling.

Preparation and crystal structure of garnet-type calcium zirconium germanate Ca4ZrGe3O12

2016 ◽  
Vol 31 (4) ◽  
pp. 292-294 ◽  
Author(s):  
V. D. Zhuravlev ◽  
A. P. Tyutyunnik ◽  
N. I. Lobachevskaya
Keyword(s):  
Crystal Structure ◽  
Unit Cell Parameter ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Cell Parameter ◽  
Polycrystalline Sample ◽  
Structural Formula ◽  
Powder Diffraction Data ◽  
Structural Refinement ◽  
X Ray

A polycrystalline sample of Ca4ZrGe3O12 was synthesized using the nitrate–citrate method and heated at 850–1100 °C. Structural refinement based on X-ray powder diffraction data showed that the crystal structure is of the garnet type with a cubic unit-cell parameter [a = 12.71299(3) Å] and the space group Ia$\bar 3$d. The structural formula is presented as Ca3[CaZr]octa[Ge]tetraO12.

Synthesis, single-crystal structure determination and Raman spectrum of Cu[C(CN)3]2·2 NH3

2015 ◽  
Vol 70 (3) ◽  
pp. 177-181
Author(s):  
Olaf Reckeweg ◽  
Armin Schulz ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Single Crystals ◽  
Structure Determination ◽  
Aqueous Ammonia ◽  
Ambient Conditions ◽  
Light Blue ◽  
Cell Parameters ◽  
First Time

AbstractTransparent, light blue crystals of Cu[C(CN)3]2·2 NH3 were obtained by dissolving Cu[C(CN)3]2 in aqueous ammonia and subsequent evaporation of the solvent under ambient conditions. Cu[C(CN)3]2·2 NH3 crystallizes in the space group C2/c (no. 15, Z = 4) with the cell parameters a = 1291.9(3), b = 753.18(15) and c = 1200.8(2) pm, and β = 92.68(3)°. The nature of the tricyanomethanide anion and the ammonia molecules were verified by Raman spectroscopy. Single crystals of Ag[C(CN)3] and Cu[C(CN)3]2 were synthesized, the known structures were confirmed and their Raman spectra were recorded for the first time for comparison.

About the crystal structure of La1−xSrxCoO3−δ (0≤x≤0.6)

1996 ◽  
Vol 11 (1) ◽  
pp. 31-34 ◽  
Author(s):  
Nicole M. L. N. P. Closset ◽  
René H. E. van Doorn ◽  
Henk Kruidhof ◽  
Jaap Boeijsma
Keyword(s):  
Crystal Structure ◽  
Unit Cell Parameter ◽  
Cell Parameter ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

The crystal structure of La1−xSrxCoO3−δ (0≤x≤0.6) has been studied, using powder X-Ray diffraction. The crystal structure shows a transition from rhombohedral distorted perovskite for LaCoO3−δ into cubic perovskite for La0.4Sr0.6CoO3−δ. The cubic unit cell parameter is ac=3.8342(1) Å for La0.4Sr0.6CoO3−δ, the space group probably being Pm3m. Using a hexagonal setting, the cell parameters for La0.5Sr0.5CoO3−δ, are a=5.4300(3) Å, c=13.2516(10) Å; a=5.4375(1) Å, c=13.2313(4) Å for La0.6Sr0.4CoO3−δ; a=5.4437(1) Å, c=13.2085(5) Å for La0.7Sr0.3CoO3−δ; a=5.4497(2) Å, c=13.1781(6) Å for La0.8Sr0.2CoO3−δ and a=5.4445(2) Å, c=13.0936(6) Å for LaCoO3−δ with the space group probably being R3c.

Dynamics of the crystal structure of tin-based type-I clathrates with different degrees of disorder in their cationic frameworks

2017 ◽  
Vol 19 (40) ◽  
pp. 27725-27730 ◽  
Author(s):  
V. V. Novikov ◽  
K. S. Pilipenko ◽  
A. V. Matovnikov ◽  
N. V. Mitroshenkov ◽  
B. I. Kornev ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Heat Capacity ◽  
Unit Cell Parameter ◽  
Lattice Dynamics ◽  
Cell Parameter ◽  
Unit Cell ◽  
Type I

The temperature dependencies of heat capacity and cubic unit cell parameter for type-I clathrates were obtained to determine the influence of the concentration of vacancies and substituting atoms on the lattice dynamics.

scholarly journals Crystal Structure of an Anisotropic Pyrope Garnet That Contains Two Cubic Phases

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1320
Author(s):  
Sytle M. Antao
Keyword(s):  
Crystal Structure ◽  
Unit Cell Parameter ◽  
Cell Parameter ◽  
Rietveld Method ◽  
Unit Cell ◽  
Cubic Phase ◽  
Average Composition ◽  
Weight Percentage ◽  
Cubic Phases ◽  
De Beers

The crystal structure of two different samples of pyrope garnet, ideally Mg3Al2Si3O12, from South Africa was refined using the Rietveld method, space group Ia3¯d, and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Sample 1 from Wesselton Mine is a single cubic phase and is optically isotropic. Electron-probe microanalysis (EPMA) provided an average composition {Mg2.30Fe2+0.26Ca0.42Mn2+0.02}∑3[Al1.53Fe3+0.06Cr3+0.40Ti4+0.01Fe2+0.01]∑2Si3O12, which contains a significant amount of Cr cations. The unit-cell parameter (Å) and bond distances (Å) are a = 11.56197(1) Å, average <Mg-O> = 2.2985, Al-O = 1.9101(4), and Si-O = 1.6343(3) Å. Sample 2 from De Beers Diamond Mine has an average composition {Mg2.33Fe2+0.33Ca0.33Mn2+0.01}∑3[Al1.73Fe3+0.12Cr3+0.06Ti4+0.05Fe2+0.05]∑2Si3O12 and is a fine-scale intergrowth of two cubic phases. The weight percentage, unit-cell parameter (Å), and bond distances (Å) for phase 2a are 62.2(1)%, a = 11.56185(1) Å, average <Mg-O> = 2.3006, Al-O = 1.9080(4), Si-O = 1.6334(4) Å. The corresponding values for phase 2b are 37.8(1)%, a = 11.53896(1) Å, average <Mg-O> = 2.2954, Al-O = 1.9020(6), Si-O = 1.6334(6) Å. The two cubic phases in sample 2 cause the crystal to be optically anisotropic because of strain induce birefringence. The unit-cell parameter and bond distances for sample 1 are similar to those in phase 2a.

scholarly journals Packing polymorphism in the structure oftrans-aqua[N,N′-bis(salicylidene)ethane-1,2-diamine-κ4O,N,N′,O′]chloridomanganese(III) monohydrate

2018 ◽  
Vol 74 (12) ◽  
pp. 1778-1782
Author(s):  
Juan Alberto Reyes Perea ◽  
Sylvain Bernès ◽  
Ma Guadalupe Quintero Téllez
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Unit Cell Parameter ◽  
Molecular Conformation ◽  
Cell Parameter ◽  
Title Complex ◽  
Unit Cell ◽  
Alternative Synthesis ◽  
Space Group ◽  
Structural Database

The crystal structure of the title complex (systematic name:trans-aquachlorido{2,2′[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato-κ4O,N,N′,O′}manganese(III) monohydrate), [Mn(C16H14N2O2)Cl(H2O)]·H2O has been reported previously in the space groupP21/n[Panjaet al.(2003).Polyhedron,22, 1191–1198]. We obtained the same hydrated complex through an alternative synthesis, and crystallized a new polymorph, in the space groupP21. The molecular conformation of the complex is virtually unmodified, but the absence of the glide plane in the new polymorph halves the unit-cell parameterc, affording a non-centrosymmetric crystal structure withZ= 2, while the previously reported crystal is centrosymmetric withZ= 4. Both phases represent a case of packing polymorphism, similar to other dimorphic crystal structures retrieved from the Cambridge Structural Database.

Crystal-chemistry of sulfates from the Apuan Alps (Tuscany, Italy). VI. Tl-bearing alum-(K) and voltaite from the Fornovolasco mining complex

2020 ◽  
Vol 105 (7) ◽  
pp. 1088-1098 ◽  
Author(s):  
Cristian Biagioni ◽  
Daniela Mauro ◽  
Marco Pasero ◽  
Elena Bonaccorsi ◽  
Giovanni Orazio Lepore ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Unit Cell Parameter ◽  
Cell Parameter ◽  
Unit Cell ◽  
Partial Substitution ◽  
Chemical Formula ◽  
Space Group ◽  
X Ray ◽  
Mining Complex ◽  
Apuan Alps

Abstract Thallium-bearing samples of alum-(K) and voltaite from the Fornovolasco mining complex (Apuan Alps, Tuscany, Italy) have been characterized through X-ray diffraction, chemical analyses, micro-Raman, infrared (FTIR), Mössbauer, and X-ray absorption spectroscopy (XAS). Alum-(K) occurs as anhedral colorless grains or rarely as octahedral crystals, up to 5 mm. Electron-microprobe analysis points to the chemical formula (K0.74Tl0.10)Σ0.84(Al0.84Fe0.14)Σ0.98S2.03O8·12H2O. The occurrence of minor NH4+ was detected through FTIR spectroscopy. Its unit-cell parameter is a = 12.2030(2) Å, V = 1817.19(9) Å3, space group Pa3. Its crystal structure has been refined down to R1 = 0.0351 for 648 reflections with Fo &gt; 4σ(Fo) and 61 refined parameters. The crystal structure refinement agrees with the partial substitution of K by 12 mol% Tl. This substitution is confirmed by XAS data, showing the presence of Tl+ having a first coordination shell mainly formed by 6 O atoms at 2.84(2) Å. Voltaite occurs as dark green cubic crystals, up to 1 mm in size. Voltaite is chemically zoned, with distinct domains having chemical formula (K1.94Tl0.28)Σ2.22(Fe3.572+Mg0.94Mn0.55)Σ5.06Fe3.063+Al0.98S11.92O48·18H2O and (K2.04Tl0.32)Σ2.36(Fe3.832+Mg0.91Mn0.29)Σ5.03Fe3.053+Al0.97S11.92O48·18H2O, respectively. Infrared spectroscopy confirmed the occurrence of minor NH4+ also in voltaite. Its unit-cell parameter is a = 27.2635 Å, V = 20265(4) Å3, space group Fd3c. The crystal structure was refined down to R1 = 0.0434 for 817 reflections with Fo &gt; 4σ(Fo) and 87 refined parameters. The partial replacement of K by Tl is confirmed by the structural refinement. XAS spectroscopy showed that Tl+ is bonded to six O atoms, at 2.89(2) Å. The multi-technique characterization of thallium-bearing alum-(K) and voltaite improves our understanding of the role of K-bearing sulfates in immobilizing Tl in acid mine drainage systems, temporarily avoiding its dispersion in the environment.

Effect of solution acidity on the crystallization of polychromates in uranyl-bearing systems: synthesis and crystal structures of Rb2[(UO2)(Cr2O7)(NO3)2] and two new polymorphs of Rb2Cr3O10

2021 ◽  
Vol 236 (1-2) ◽  
pp. 11-21
Author(s):  
Evgeny V. Nazarchuk ◽  
Oleg I. Siidra ◽  
Dmitry O. Charkin ◽  
Stepan N. Kalmykov ◽  
Elena L. Kotova
Keyword(s):  
Crystal Structure ◽  
Aqueous Solutions ◽  
Crystal Structures ◽  
Hydrothermal Treatment ◽  
Ambient Conditions ◽  
Screw Axis ◽  
3D Framework ◽  
Solution Acidity

Abstract Three new rubidium polychromates, Rb2[(UO2)(Cr2O7)(NO3)2] (1), γ-Rb2Cr3O10 (2) and δ-Rb2Cr3O10 (3) were prepared by combination of hydrothermal treatment at 220 °C and evaporation of aqueous solutions under ambient conditions. Compound 1 is monoclinic, P 2 1 / c $P{2}_{1}/c$ , a = 13.6542(19), b = 19.698(3), c = 11.6984(17) Å, β = 114.326(2)°, V = 2867.0(7) Å3, R 1 = 0.040; 2 is hexagonal, P 6 3 / m $P{6}_{3}/m$ , a = 11.991(2), c = 12.828(3) Å, γ = 120°, V = 1597.3(5) Å3, R 1 = 0.031; 3 is monoclinic, P 2 1 / n $P{2}_{1}/n$ , a = 7.446(3), b = 18.194(6), c = 7.848(3) Å, β = 99.953(9)°, V = 1047.3(7) Å3, R 1 = 0.037. In the crystal structure of 1, UO8 bipyramids and NO3 groups share edges to form [(UO2)(NO3)2] species which share common corners with dichromate Cr2O7 groups producing novel type of uranyl dichromate chains [(UO2)(Cr2O7)(NO3)2]2−. In the structures of new Rb2Cr3O10 polymorphs, CrO4 tetrahedra share vertices to form Cr3O10 2− species. The trichromate groups are aligned along the 63 screw axis forming channels running in the ab plane in the structure of 2. The Rb cations reside between the channels and in their centers completing the structure. The trichromate anions are linked by the Rb+ cations into a 3D framework in the structure of 3. Effect of solution acidity on the crystallization of polychromates in uranyl-bearing systems is discussed.

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