scholarly journals New Ca2.90(Me2+)0.10(PO4)2 β-tricalcium Phosphates with Me2+ = Mn, Ni, Cu: Synthesis, Crystal-Chemistry, and Luminescence Properties

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 288 ◽  
Author(s):  
Angela Altomare ◽  
Rosanna Rizzi ◽  
Manuela Rossi ◽  
Asmaa El Khouri ◽  
Mohammed Elaatmani ◽  
...  
Keyword(s):  
Tricalcium Phosphate ◽  
Rietveld Method ◽  
Unit Cell ◽  
Luminescence Properties ◽  
Luminescence Spectroscopy ◽  
Luminescence Spectra ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tricalcium Phosphates

C a 2.90 M e 0.10 2 + ( P O 4 ) 2 (with Me = Mn, Ni, Cu) β-tricalcium phosphate (TCP) powders were synthesized by solid-state reaction at T = 1200 °C and investigated by means of a combination of scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, and luminescence spectroscopy. SEM morphological analysis showed the run products to consist of sub spherical microcrystalline aggregates, while EDS semi-quantitative analysis confirmed the nominal Ca/Me composition. The unit cell and the space group were determined by X-ray powder diffraction data showing that all the compounds crystallize in the rhombohedral R3c whitlockite-type structure, with the following unit cell constants: a = b = 10.41014(19) Å, c = 37.2984(13) Å, and cell volume V = 3500.53(15) Å3 (Mn); a = b = 10.39447(10) Å, c = 37.2901(8) Å; V = 3489.22(9) Å3 (Ni); a = b = 10.40764(8) Å, c = 37.3158(6) Å, V = 3500.48(7) Å3 (Cu). The investigation was completed with the structural refinement by the Rietveld method. The FTIR spectra are similar to those of the end-member Ca β-tricalcium phosphate (TCP), in agreement with the structure determination, and show minor band shifts of the (PO4) modes with the increasing size of the replacing Me2+ cation. Luminescence spectra and decay curves revealed significant luminescence properties for Mn and Cu phases.

scholarly journals Characterization and Luminescence of Eu3+- and Gd3+-Doped Hydroxyapatite Ca10(PO4)6(OH)2

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 806 ◽  
Author(s):  
Veronica Paterlini ◽  
Marco Bettinelli ◽  
Rosanna Rizzi ◽  
Asmaa El Khouri ◽  
Manuela Rossi ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rietveld Method ◽  
Structure Characterization ◽  
Luminescence Spectroscopy ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Strong Luminescence ◽  
Bio Imaging

Luminescence properties of europium-doped Ca10-xEux(PO4)6(OH)2 (xEu = 0, 0.01, 0.02, 0.10 and 0.20) and gadolinium-doped hydroxyapatite Ca9.80Gd0.20(PO4)6(OH)2 (HA), synthesized via solid-state reaction at T = 1300 °C, were investigated using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), and luminescence spectroscopy. Crystal structure characterization (from unit cell parameters determination to refined atomic positions) was achieved in the P63/m space group. FTIR analyses show only slight band shifts of (PO4) modes as a function of the rare earth concentration. Structural refinement, achieved via the Rietveld method, and luminescence spectroscopy highlighted the presence of dopant at the Ca2 site. Strong luminescence was observed for all Eu- and Gd-doped samples. Our multi-methodological study confirms that rare-earth (RE)-doped synthetic hydroxyapatites are promising materials for bio-imaging applications.

X-ray diffraction studies on the effect of ball-milling speed on the structure of Cu(In,Ga)Se2 nanoparticles

2013 ◽  
Vol 28 (S1) ◽  
pp. S28-S31 ◽  
Author(s):  
L. Fu ◽  
Y.Q. Guo ◽  
S. Zheng
Keyword(s):  
Ball Milling ◽  
Least Squares Method ◽  
Unit Cell ◽  
Chalcopyrite Structure ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Cigs Nanoparticles

Cu(In,Ga)Se2 (CIGS) semiconductors were prepared by arc melting and the vacuum solid reaction. CIGS nanoparticles were synthesized by the mechanical alloy method. The influences of various ball-milling speeds on phase structures for CIGS nanoparticles were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystal structures and unit-cell parameters of CIGS nanoparticles were determined using TREOR program and the least squares method. A Rietveld structural refinement was used to determine the atomic occupations and atomic numbers of CIGS prepared under various ball-milling speeds. The least size of agglomerated CIGS nanoparticles should be around 200 nm. CIGS nanoparticles milled at various milling speeds with a tetragonal chalcopyrite structure were obtained according to XRD analyses. However, Ga content in CIGS depends on milling speeds. Based on the structural refinements, the unit-cell parameters are a = 5.693(8)–5.744(9) Å and c = 11.334(9)–11.524(4) Å with gallium content ranging from 0.3 to 0.5. The atomic occupations are corresponding to the 4a crystal site for Cu atoms, the 4b site for In and the 8d site for Se. Ga prefers to occupy the 4b crystal site.

Crystal structure and powder X-ray diffraction data for new Tb3CuAl3Ge2 compound

2015 ◽  
Vol 30 (1) ◽  
pp. 63-66 ◽  
Author(s):  
Chao Zeng ◽  
Guoqiang Lin ◽  
Weijing Zeng ◽  
Wei He
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Unit Cell ◽  
Type Structure ◽  
X Ray Diffraction ◽  
Quaternary Compound ◽  
Space Group ◽  
X Ray

The crystal structure of new Tb3CuAl3Ge2 quaternary compound was studied by the Rietveld method from powder X-ray diffraction (XRD) data. The Tb3CuAl3Ge2 compound crystallized in the hexagonal Y3NiAl3Ge2-type structure with space group P-62m (no. 189) and lattice parameters a = 7.0041(2) Å, c = 4.1775(1) Å, V = 177.48 Å3. There is only one formula in each unit cell, Z = 1, and the density of Tb3CuAl3Ge2 is ρx = 7.1696 g cm−3. The reliability factors characterizing the Rietveld refinement results are Rp = 6.43%, Rwp = 8.65%, RB = 4.81%, and RF = 4.09%, respectively. The powder XRD data of Tb3CuAl3Ge2 were presented and the reliability of indexation is F30 = 120.9(0.0073, 34).

scholarly journals On the crystal structure of the ordered vacancy compound Cu3In5Te9

2019 ◽  
Vol 65 (4 Jul-Aug) ◽  
pp. 360 ◽  
Author(s):  
G. E. Delgado ◽  
C. Rincón ◽  
G. Marroquin
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structural Models ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

The crystal structure of the ordered vacancy compound (OVC) Cu3In5Te9 was analyzed using powder X-ray diffraction data. Several structural models were derived from the structure of the Cu-poor Cu-In-Se compound b-Cu0.39In1.2Se2 by permuting the cations in the available site positions. The refinement of the best model by the Rietveld method in the tetragonal space group P2c (Nº 112), with unit cell parameters a = 6.1852(2) Å, c = 12.3633(9) Å, V = 472.98(4) Å3, led to Rp = 7.1 %, Rwp = 8.5 %, Rexp = 6.4 %, S = 1.3 for 162 independent reflections. This model has the following Wyckoff site atomic distribution: Cu1 in 2e (0,0,0); In1 in 2f (½,½,0), In2 in 2d (0,½,¼); Cu2-In3 in 2b (½,0,¼); in 2a (0,0,¼); Te in 8n (x,y,z).

Structural Refinement by the Rietveld Method on Clinkers Obtained from Waste from Pulp and Paper Mills

2018 ◽  
Vol 912 ◽  
pp. 175-179 ◽  
Author(s):  
Lisandro Simão ◽  
J. Jiusti ◽  
N.J. Lóh ◽  
D. Hotza ◽  
F. Raupp-Pereira ◽  
...  
Keyword(s):  
Rietveld Method ◽  
Pulp And Paper ◽  
Cement Industry ◽  
Processing Conditions ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
X Ray ◽  
Biomass Ashes

Pulp and paper mills have a process that generates waste with high levels of CaO and SiO2, which can be valued as an alternative mineral source in the cement industry. In this work the lime mud, biomass ashes and WWTP sludge are used in the production of clinker. Analysis of X-ray diffraction (XRD) confirmed the crystalline phases calcite and quartz. Chemical analysis by X-ray fluorescence (XRF) identified Al2O3, CaO and SiO2, providing support for the calculation of theoretical stages by applying the Bogue equations. Five formulations and three processing temperatures (1350, 1400, 1455 °C) were studied. The products obtained and an ordinary Portland cement (OPC) were characterized by XRD with quantification by the Rietveld method. The results showed that the processing conditions used produced belíticos (higher content of C2S) and Portland (C3S content greater) ecoclinker.

(Ba, Sr)3MgSi2O8 structure change caused by Ba/Sr replacement

2014 ◽  
Vol 30 (1) ◽  
pp. 40-51 ◽  
Author(s):  
Yoshinori Yonezaki
Keyword(s):  
Raman Spectroscopy ◽  
Interlayer Space ◽  
Rietveld Method ◽  
Structure Change ◽  
Solid Solution Series ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Size Mismatch ◽  
Structural Symmetry ◽  
X Ray

Crystal structure of BaxSr3–xMgSi2O8 has been determined by Raman spectroscopy and X-ray diffraction. The solid solution series have glaserite-type layered structures made of corner-sharing SiO4 tetrahedra and MgO6 octahedra. Ba2+ and Sr2+ ions are sandwiched in between the layers. Raman spectroscopy has found that structural symmetry changes at x = 0.5 and 2.5. Structural refinement by the Rietveld method has clarified that the symmetry changes occur among C2 (Z = 4), P${\bar 3}$m1 (Z = 1), and P${\bar 3}$ (Z = 3). They originate in SiO4 tilting caused by size mismatch between alkali–earth cations and their site spaces. For x ≤ 0.5, SiO4 tilting occur every other interlayer space, whereas for x ≥ 2.5, all the SiO4 tilt.

scholarly journals The structure of kaliophilite KAlSiO4, a long-lasting crystallographic problem

IUCrJ ◽  
2020 ◽  
Vol 7 (6) ◽  
pp. 1070-1083 ◽  
Author(s):  
Enrico Mugnaioli ◽  
Elena Bonaccorsi ◽  
Arianna E. Lanza ◽  
Erik Elkaim ◽  
Virginia Diez-Gómez ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Structural Features ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Channel System ◽  
X Ray ◽  
Cell Parameters ◽  
Peak Broadening ◽  
Structure Solution

Kaliophilite is a feldspathoid mineral found in two Italian magmatic provinces and represents one of the 12 known phases with composition close to KAlSiO4. Despite its apparently simple formula, the structure of this mineral revealed extremely complex and resisted structure solution for more than a century. Samples from the Vesuvius–Monte Somma and Alban Hills volcanic areas were analyzed through a multi-technique approach, and finally the crystal structure of kaliophilite was solved using 3D electron diffraction and refined against X-ray diffraction data of a twinned crystal. Results were also ascertained by the Rietveld method using synchrotron powder intensities. It was found that kaliophilite crystallizes in space group P3 with unit-cell parameters a = 27.0597 (16), c = 8.5587 (6) Å, V = 5427.3 (7) Å3 and Z = 54. The kaliophilite framework is a variant of the tridymite topology, with alternating SiO4 and AlO4 tetrahedra forming sheets of six-membered rings (63 nets), which are connected along [001] by sharing the apical oxygen atoms. Considering the up (U) and down (D) orientations of the linking vertex, kaliophilite is the first framework that contains three different ring topologies: nine (1-3-5) (UDUDUD) rings, six (1-2-3) (UUUDDD) rings and twelve (1-2-4) (UUDUDD) rings. This results in a relatively open (19.9 tetrahedra nm−3) channel system with multiple connections between the double six-ring cavities. Such a framework requires a surprisingly large unit cell, 27 times larger than the cell of kalsilite, the simplest phase with the same composition. The occurrence of some Na for K substitution (3–10%) may be related to the characteristic structural features of kaliophilite. Micro-twinning, pseudo-symmetries and anisotropic hkl-dependent peak broadening were also detected, and they may account for the elusive character of the kaliophilite crystal structure.

A crystal structure of ultra-dispersed form of polytetrafluoroethylene based on X-ray powder diffraction data

2004 ◽  
Vol 19 (3) ◽  
pp. 219-224 ◽  
Author(s):  
V. M. Bouznik ◽  
S. D. Kirik ◽  
L. A. Solovyov ◽  
A. K. Tsvetnikov
Keyword(s):  
Powder Diffraction ◽  
Rietveld Method ◽  
Unit Cell ◽  
Two Dimensional ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Rotational Displacement ◽  
X Ray ◽  
Dimensional Unit ◽  
Disordered Atoms

An X-Ray powder diffraction study of ultra-dispersed polytetrafluoroethylene was carried out. As well as a regular polytetrafluoroethylene the ultra-dispersed form contents a high proportion of the crystalline phase. The X-ray diffraction pattern could be described with two-dimensional hexagonal unit cell [a=5.685(1) Å, symmetry group p6mm]. Structural modeling with a continuous electron density approach as well as with a discrete disordered atoms distribution was accomplished. The model was refined using the Rietveld method. The structure is characterized by a spiral arrangement of polymers (CF2-)n along the z-axis with complete mutual disordering by rotational displacement around z, as well as a partial molecular translation along the z-axis. Molecular disordering results in a systematic absence of reflections with 1≠0 and as a sequence in two-dimensional unit cell effect. The presence of complete rotational disordering distinguishes the ultra-dispersed form of polytetrafluoroethylene from the standard one (fluoroplast-4), where only partial disordering is observed.

Crystal structure of Cr2[Ni(CN)4]3·10H2O

1996 ◽  
Vol 11 (4) ◽  
pp. 318-320 ◽  
Author(s):  
A. Ratuszna ◽  
S. Juszczyk ◽  
G. Malłecki
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Rietveld Method ◽  
Unit Cell ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon And Nitrogen ◽  
Disordered Structure ◽  
Starting Model

The crystal structure of Cr2[Ni(CN)4]3·10H2O has been determined on X-ray diffraction powder data by means of the Rietveld method. The starting model was based on the isomorphic, disordered structure of Mn3[Co(CN)6]2·12H2O. At room temperature the crystal is cubic, F4¯3m, a=10.097(6) Å, V=1029.4(5) Å3. The structure is disordered and contains 1.33 formula weights per unit cell. The Ni and Cr ions are coordinated by N and C atoms, respectively, forming octahedra linked by CN groups. The water molecules replace partly the chromium, carbon, and nitrogen positions in the crystal. The final R values are: Rwp=0.032 (Rexp=0.023), RB=0.088, and DW-Stat.=1.31 (DWexp=1.8).

Structural analysis of lead magnesium niobate using synchrotron powder X-ray diffraction and the Rietveld method

2016 ◽  
Vol 72 (3) ◽  
pp. 404-409 ◽  
Author(s):  
Ashok Bhakar ◽  
Adityanarayan H. Pandey ◽  
M. N. Singh ◽  
Anuj Upadhyay ◽  
A. K. Sinha ◽  
...  
Keyword(s):  
Cell Volume ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Rietveld Method ◽  
Unit Cell ◽  
Lead Magnesium Niobate ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lead Magnesium

The room-temperature synchrotron powder X-ray diffraction pattern of the single phase perovskite lead magnesium niobate (PMN) has shown significant broadening in theqrange ∼ 5–7 Å−1compared with standard LaB6synchrotron powder X-ray diffraction data, taken under similar conditions. This broadening/asymmetry lies mainly towards the lower 2θ side of the Bragg peaks. Attempts to fit this data with the paraelectric cubic phase (Pm\bar 3m) and the local rhombohedral phase (R3m) corresponding to polar nanoregions (PNRs) are made using the Rietveld method. Rietveld refinements show that neither cubic (Pm\bar 3m) nor rhombohedral (R3m) symmetry can fit this XRD pattern satisfactorily. The two-phase refinement fits the experimental data satisfactorily and suggests that the weight percentage of the PNRs is approximately 12–16% at room temperature. The unit-cell volume of these rhombohedral PNRs is approximately 0.15% larger than that of the unit cell volume of the paraelectric cubic phase.

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