scholarly journals Synthesis, Characterization, and Crystal Structure Refinement of Lanthanum and Yttrium Substituted Polycrystalline 2M Type Zirconolite Phases: Ca1-xMxZrTi2O7 (M = Y, La and x = 0.2)

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ashish Bohre ◽  
Kalpana Avasthi ◽  
O. P. Shrivastava
Keyword(s):  
Structure Refinement ◽  
Rietveld Analysis ◽  
Strength Analysis ◽  
Cation Site ◽  
Interatomic Distances ◽  
X Ray ◽  
Cell Parameters ◽  
Standard Values ◽  
Analysis System ◽  
Good Agreement

Solid phases of zirconolite-2M with composition Ca0.8M0.2ZrTi2O7 (M = La, Y) have been synthesized through ceramic route and their structures refined to a satisfactory convergence using Rietveld analysis. Zirconolites crystallize in space group C2/c with Z = 8. The powder diffraction data of Ca0.8Y0.2ZrTi2O7 (CZTY) and Ca0.8La0.2ZrTi2O7 (CZTLa) have been subjected to General Structural Analysis System software to arrive at a satisfactory structure fit with Rp = 0.1128 and Rwp = 0.1805 for CZTY and Rp = 0.1178 and Rwp = 0.1874 for CZTLa, respectively. The unit cell parameters are a = 10.1708 (6) Ǻ, b = 6.2711 (4), and c = 11.2779 (6) Ǻ for CZTY and a = 11.2548 (6) Ǻ, b = 6.2601 (4), and c=11.2606 (7) Ǻ for CZTLa. Calculated interatomic distances and bond angles are in good agreement with their standard values. Particle size along prominent reflecting planes calculated by Scherrer’s formula ranges between 67 and 107 nm. The polyhedral (CaO8, ZrO7, and TiO6/TiO5) distortions and valence calculation based on bond strength analysis have been reported. The compositions of the zirconolites were determined using energy dispersive X-ray (EDAX) analysis. Cation site occupancies were determined by applied compositional constraints which were found consistent with the expected zirconolite-2M cation site occupancies.

Site occupancy in richterite-winchite from Libby, Montana, USA, by FTIR spectroscopy

2007 ◽  
Vol 71 (1) ◽  
pp. 93-104 ◽  
Author(s):  
G. Iezzi ◽  
G. Della Ventura ◽  
F. Bellatreccia ◽  
S. Lo Mastro ◽  
B. R. Bandli ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Rietveld Analysis ◽  
Published Data ◽  
X Ray Diffraction ◽  
Cation Site ◽  
X Ray ◽  
Powder Samples ◽  
Frequency Components

AbstractThree natural amphibole samples collected from the former vermiculite mine near Libby, Montana. USA, have been analysed by Rietveld X-ray powder diffraction (XRPD) refinement and Fourier transform infrared spectroscopy (FTIR) in the OH-stretching region. The same materials have been analysed previously by electron microprobe analysis (EMPA), Mössbauer spectroscopy and structure refinement (SREF) single crystal X-ray diffraction (SC-XRD), which revealed that these amphiboles have a crystal chemical formula very close to an intermediate composition between winchite and richterite, i.e. AA0.5BNaCaCMg4.5M3+T0.5Si8O22(OH)2 (A = Na and/or K; M3+ = Fe3+ and/or Al). The Rietveld analysis showed the powder samples used for the experiments here to be composed only of amphibole. This in turn allowed us to use FTIR OH-stretching data to derive cation ordering on these powder samples. The three FTIR spectra are quite similar and up to four components can be fitted to the patterns. The two lower-frequency components (labelled A and B) can be attributed to a local O(3)-H dipole surrounded by M(1)M(3)Mg3 and M(1)M(3)Mg2Fe2+; (respectively), an empty A site and rSi8 environments; on the contrary, the higher-frequency C and D bands indicate the presence of an occupied A site. The FTIR OH-stretching data alone allow us to calculate the site occupancy of the A, M(1)–M(3) and T sites with confidence, as compared with previously published data. By contrast M(4)- and M(2)-site occupancies are more difficult to evaluate. This study takes advantage of the large database of well characterized synthetic amphiboles, built over the last two decades. The comparison of vibrational spectroscopy data with micro-chemical and crystallographic data reported in this study demonstrate that the FTIR OH-stretching method alone is a valuable and rapid method to derive or at least sensibly constrain site occupancy for natural amphiboles. A much more detailed cation site occupancy can be obtained by combining micro-chemical and FTIR OH-stretching data.

scholarly journals Synthesis, Structural Study and Thermal Expansion of Cesium Dititanium Tris(Phosphate)

2010 ◽  
Vol 12 (3,4) ◽  
pp. 189 ◽  
Author(s):  
E.A. Asabina ◽  
V.I. Pet'kov
Keyword(s):  
Thermal Expansion ◽  
Structure Refinement ◽  
Rietveld Analysis ◽  
Framework Structure ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Trigonal System ◽  
Cubic System

<p>The new phosphate CsTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> was synthesized by precipitating method and characterized by scanning electron microscopy with energy-dispersive X-ray microanalyzer, X-ray powder diffraction and IR-spectroscopy. The structure refinement of the phosphate was carried out by a Rietveld analysis. CsTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> crystallizes with the cubic system (space group <em>Ia</em><em>3</em><em>d</em>), its unit-cell parameters: <em>a</em> = 19.909(5) Å, <em>V</em> = 7892(1) Å<sup>3</sup>. It has the framework structure formed by TiO<sub>6</sub> octahedra and PO<sub>4</sub> tetrahedra, the two type positions of Cs<sup>+</sup> cations are in the cavities of the structure. CsTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> structure features are discussed. The results of the undertaken study showed that cesium dititanium tris(phosphate) crystal structure differs from its isoformulic analogues CsZr<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> and AM<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> (A = Na, K, Rb; M = Ti, Zr), crystallizing in the trigonal system (space group <em>R</em> <em>c</em>) with the kosnarite type. Thermal expansion of the CsTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> was studied: α<em><sub>a</sub></em> = 7.85∙10<sup>-6</sup> °C<sup>-1</sup>, α<em><sub>V</sub></em> = 23.5∙10<sup>-6</sup> °C<sup>-1 </sup>in the range 25–800 °C.</p>

Towards a revisitation of vesuvianite-group nomenclature: the crystal structure of Ti-rich vesuvianite from Alchuri, Shigar Valley

2016 ◽  
Vol 72 (5) ◽  
pp. 744-752 ◽  
Author(s):  
Sergey M. Aksenov ◽  
Nikita V. Chukanov ◽  
Vyacheslav S. Rusakov ◽  
Taras L. Panikorovskii ◽  
Ramiza K. Rastsvetaeva ◽  
...  
Keyword(s):  
Octahedral Site ◽  
Structure Refinement ◽  
Optical Measurements ◽  
Transition Elements ◽  
X Ray ◽  
Cell Parameters ◽  
Tetragonal Unit Cell ◽  
Northern Areas ◽  
Shigar Valley

Vesuvianite containing 5.85 wt% TiO2from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement,27Al NMR,57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are:a= 15.5326 (2),c= 11.8040 (2) Å, space groupP4/nnc. The structure was refined to finalR1= 0.031,wR2= 0.057 for 11247I> 2σ(I). A general crystal-chemical formula of studied sample can be written as follows (Z= 2):[8–9](Ca17.1Na0.9)[8]Ca1.0[5](Fe2+0.44Fe3+0.34Mg0.22)[6](Al3.59Mg0.41)[6](Al4.03Ti2.20Fe3+1.37Fe2+0.40) (Si18O68) [(OH)5.84O2.83F1.33]. The octahedral siteY2 is Al-dominant and does not contain transition elements. Another octahedral siteY3 is also Al-dominant and contains Fe2+, Fe3+and Ti. The siteY1 is split intoY1aandY1bpredominantly occupied by Fe2+and Fe3+, respectively. The role of theY1 site in the diversity of vesuvianite-group minerals is discussed.

Arrheniusite-(Ce), CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11, a New Member of the Vicanite Group, from the Östanmossa Mine, Norberg, Sweden

2021 ◽  
Author(s):  
Dan Holtstam ◽  
Luca Bindi ◽  
Paola Bonazzi ◽  
Hans-Jürgen Förster ◽  
Ulf B. Andersson
Keyword(s):  
Structure Refinement ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
Epma Data ◽  
X Ray ◽  
Cell Parameters ◽  
Greenish Yellow ◽  
The Ideal

ABSTRACT Arrheniusite-(Ce) is a new mineral (IMA 2019-086) from the Östanmossa mine, one of the Bastnäs-type deposits in the Bergslagen ore region, Sweden. It occurs in a metasomatic F-rich skarn, associated with dolomite, tremolite, talc, magnetite, calcite, pyrite, dollaseite-(Ce), parisite-(Ce), bastnäsite-(Ce), fluorbritholite-(Ce), and gadolinite-(Nd). Arrheniusite-(Ce) forms anhedral, greenish-yellow translucent grains, exceptionally up to 0.8 mm in diameter. It is optically uniaxial (–), with ω = 1.750(5), ε = 1.725(5), and non-pleochroic in thin section. The calculated density is 4.78(1) g/cm3. Arrheniusite-(Ce) is trigonal, space group R3m, with unit-cell parameters a = 10.8082(3) Å, c = 27.5196(9) Å, and V = 2784.07(14) Å3 for Z = 3. The crystal structure was refined from X-ray diffraction data to R1 = 3.85% for 2286 observed reflections [Fo &gt; 4σ(Fo)]. The empirical formula for the fragment used for the structural study, based on EPMA data and results from the structure refinement, is: (Ca0.65As3+0.35)Σ1(Mg0.57Fe2+0.30As5+0.10Al0.03)Σ1[(Ce2.24Nd2.13La0.86Gd0.74Sm0.71Pr0.37)Σ7.05(Y2.76Dy0.26Er0.11Tb0.08Tm0.01Ho0.04Yb0.01)Σ3.27Ca4.14]Σ14.46(SiO4)3[(Si3.26B2.74)Σ6O17.31F0.69][(As5+0.65Si0.22P0.13)Σ1O4](B0.77O3)F11; the ideal formula obtained is CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11. Arrheniusite-(Ce) belongs to the vicanite group of minerals and is distinct from other isostructural members mainly by having a Mg-dominant, octahedrally coordinated site (M6); it can be considered a Mg-As analog to hundholmenite-(Y). The threefold coordinated T5 site is partly occupied by B, like in laptevite-(Ce) and vicanite-(Ce). The mineral name honors C.A. Arrhenius (1757–1824), a Swedish officer and chemist, who first discovered gadolinite-(Y) from the famous Ytterby pegmatite quarry.

Rietveld refinement of the solid-solution series: (Cu,Mg)SO4·H2O

1995 ◽  
Vol 10 (3) ◽  
pp. 189-194 ◽  
Author(s):  
C. L. Lengauer ◽  
G. Giester
Keyword(s):  
Solid Solution ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Solid Solution Series ◽  
Cation Site ◽  
Tg Analysis ◽  
X Ray ◽  
Solution Series

The kieserite-type solid-solution series of synthetic (Cu,Mg)SO4·H2O was investigated by TG-analysis and X-ray powder diffraction using the Rietveld method. Representatives with Cu≥20 mol% are triclinic distorted () analogous to the poitevinite (Cu,Fe)SO4·H2O compounds. Cation site ordering with preference of Cu for the more distorted M1 site was additionally proven by the structure refinement.

Crystal structure of potassium tetraperoxomolybdate (VI) K2[Mo(O2)4]

2005 ◽  
Vol 20 (3) ◽  
pp. 203-206 ◽  
Author(s):  
M. Grzywa ◽  
M. Różycka ◽  
W. Łasocha
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

Potassium tetraperoxomolybdate (VI) K2[Mo(O2)4] was prepared, and its X-ray powder diffraction pattern was recorded at low temperature (258 K). The unit cell parameters were refined to a=10.7891(2) Å, α=64.925(3)°, space group R−3c (167), Z=6. The compound is isostructural with potassium tetraperoxotungstate (VI) K2[W(O2)4] (Stomberg, 1988). The sample of K2[Mo(O2)4] was characterized by analytical investigations, and the results of crystal structure refinement by Rietveld method are presented; final RP and RWP are 9.79% and 12.37%, respectively.

Potassic-jeanlouisite from Leucite Hill, Wyoming, USA, ideally K(NaCa)(Mg4Ti)Si8O22O2: the first species of oxo amphibole in the sodium–calcium subgroup

2019 ◽  
Vol 83 (4) ◽  
pp. 587-593
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Giancarlo Della Ventura ◽  
Gunnar Färber
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Mineralogical Association ◽  
Sodium Calcium

AbstractPotassic-jeanlouisite, ideally K(NaCa)(Mg4Ti)Si8O22O2, is the first characterised species of oxo amphibole related to the sodium–calcium group, and derives from potassic richterite via the coupled exchange CMg–1W${\rm OH}_{{\rm \ndash 2}}^{\ndash}{} ^{\rm C}{\rm Ti}_1^{{\rm 4 +}} {} ^{\rm W}\!{\rm O}_2^{2\ndash} $. The mineral and the mineral name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification, IMA2018-050. Potassic-jeanlouisite was found in a specimen of leucite which is found in the lava layers, collected in the active gravel quarry on Zirkle Mesa, Leucite Hills, Wyoming, USA. It occurs as pale yellow to colourless acicular crystals in small vugs. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(K0.84Na0.16)Σ1.00B(Ca0.93Na1.02Mg0.04${\rm Mn}_{{\rm 0}{\rm. 01}}^{2 +} $)Σ2.00C(Mg3.85${\rm Fe}_{{\rm 0}{\rm. 16}}^{2 +} $Ni0.01${\rm Fe}_{{\rm 0}{\rm. 33}}^{3 +} {\rm V}_{{\rm 0}{\rm. 01}}^{3 +} $Ti0.65)Σ5.01T(Si7.76Al0.09Ti0.15)Σ8.00O22W[O1.53F0.47]Σ2.00. The holotype crystal is biaxial (–), with α = 1.674(2), β = 1.688(2), γ = 1.698(2), 2Vmeas. = 79(1)° and 2Vcalc. = 79.8°. The unit-cell parameters are a = 9.9372(10), b = 18.010(2), c = 5.2808(5) Å, β = 104.955(2)°, V = 913.1(2) Å3, Z = 2 and space group C2/m. The strongest eight reflections in the powder X-ray pattern [d values (in Å) (I) (hkl)] are: 2.703 (100) (151); 3.380 (87) (131); 2.541 (80) ($\bar 2$02); 3.151 (70) (310); 3.284 (68) (240); 8.472 (59) (110); 2.587 (52) (061); 2.945 (50) (221,$\bar 1$51).

scholarly journals Redetermination of Sr2PdO3 from single-crystal X-ray data

2019 ◽  
Vol 75 (1) ◽  
pp. 30-32
Author(s):  
Gohil S. Thakur ◽  
Hans Reuter ◽  
Claudia Felser ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Structure Type ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Cell Parameters ◽  
Anisotropic Displacement Parameters

The crystal structure redetermination of Sr2PdO3 (distrontium palladium trioxide) was carried out using high-quality single-crystal X-ray data. The Sr2PdO3 structure has been described previously in at least three reports [Wasel-Nielen & Hoppe (1970). Z. Anorg. Allg. Chem. 375, 209–213; Muller & Roy (1971). Adv. Chem. Ser. 98, 28–38; Nagata et al. (2002). J. Alloys Compd. 346, 50–56], all based on powder X-ray diffraction data. The current structure refinement of Sr2PdO3, as compared to previous powder data refinements, leads to more precise cell parameters and fractional coordinates, together with anisotropic displacement parameters for all sites. The compound is confirmed to have the orthorhombic Sr2CuO3 structure type (space group Immm) as reported previously. The structure consists of infinite chains of corner-sharing PdO4 plaquettes interspersed by SrII atoms. A brief comparison of Sr2PdO3 with the related K2NiF4 structure type is given.

scholarly journals Effects of pH and Ca exchange on the structure and redox state of synthetic Na-birnessite

2021 ◽  
Vol 106 (1) ◽  
pp. 15-27
Author(s):  
Chiara Elmi ◽  
Jeffrey E. Post ◽  
Peter J. Heaney ◽  
Eugene S. Ilton
Keyword(s):  
Photoelectron Spectroscopy ◽  
Water Oxidation ◽  
Structure Refinement ◽  
Oxidation Catalysis ◽  
X Ray ◽  
Cell Parameters ◽  
Ph Values ◽  
Water Oxidation Catalysis ◽  
Effects Of Ph ◽  
End Members

Abstract Birnessite-like minerals are among the most common Mn oxides in surficial soils and sediments, and they mediate important environmental processes (e.g., biogeochemical cycles, heavy metal confinement) and have novel technological applications (e.g., water oxidation catalysis). Ca is the dominant interlayer cation in both biotic and abiotic birnessites, especially when they form in association with carbonates. The current study investigated the structures of a series of synthetic Ca-birnessite analogs prepared by cation-exchange with synthetic Na-birnessite at pH values from 2 to 7.5. The resulting Ca-exchanged birnessite phases were characterized using powder X-ray diffraction and Rietveld refinement, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning and transmission electron microscopy. All samples synthesized at pH values greater than 3 exhibited a similar triclinic structure with nearly identical unit-cell parameters. The samples exchanged at pH 2 and 3 yielded hexagonal structures, or mixtures of hexagonal and triclinic phases. Rietveld structure refinement and X-ray photoelectron spectroscopy showed that exchange of Na by Ca triggered reduction of some Mn3+, generating interlayer Mn2+ and vacancies in the octahedral layers. The triclinic and hexagonal Ca-birnessite structures described in this study were distinct from Na- and H-birnessite, respectively. Therefore, modeling X-ray absorption spectra of natural Ca-rich birnessites through mixing of Na- and H-birnessite end-members will not yield an accurate representation of the true structure.

Crystallochemistry and structural studies of two newly CaSb0.50Fe1.50(PO4)3 and Ca0.50SbFe(PO4)3 Nasicon phases

2006 ◽  
Vol 21 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Abderrahim Aatiq ◽  
My Rachid Tigha ◽  
Rabia Hassine ◽  
Ismael Saadoune
Keyword(s):  
Solid State ◽  
Room Temperature ◽  
Rietveld Analysis ◽  
Structural Studies ◽  
Hexagonal Cell ◽  
Conventional Solid State Reaction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Crystallographic Structures

Crystallographic structures of two new orthophosphates Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 obtained by conventional solid state reaction techniques at 900 °C, were determined at room temperature from X-ray powder diffraction using Rietveld analysis. The two compounds belong to the Nasicon structural family. The space group is R3 for Ca0.50SbFe(PO4)3 and R3c for CaSb0.50Fe1.50(PO4)3. Hexagonal cell parameters for Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 are: a=8.257(1) Å, c=22.276(2) Å, and a=8.514(1) Å, c=21.871(2) Å, respectively. Ca2+ and vacancies in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3 are ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a quasi-ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Thus, in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3, each Ca(3a)O6 octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (◻(3b)O6) site is located between two Sb5+O6 octahedra. In [Ca]M1Sb0.50Fe1.50(PO4)3 compound (R3c space group), all M1 sites are occupied by Ca2+ and the Sb5+ and Fe3+ ions are randomly distributed within the Nasicon framework.

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