Crystal Structure of K6Nb44O113 from HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 42-43
Author(s):  
F.H. Li ◽  
C.M. Teng ◽  
J.J. Hu ◽  
F. Nagata ◽  
C. Tsuruta
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Crystal Size ◽  
Fold Axis ◽  
Structure Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tetragonal System ◽  
Small Crystal Size ◽  
Different Shapes

Different results about the crystal structure of K6Nb44O113 (KNO) were obtained by X-ray diffraction analysis[1,2]. This might be due to the small crystal size and the impurity of crystalline powders. Such sample are suitable for HREM investigation. Teng et al. studied the crystal by electron diffraction and HREM[3]. They compared the image of KNO with the structure model of Rb3Nb54O146(RNO) proposed by Gatehouse et al.[4]. The latter’s structure which is formed by Nb-O octahedra belongs to the tetragonal system and contains tunnels of different shapes along the four-fold axis(Fig.1). An image of KNO given by Teng et al. shows four-leaf and three-leaf shaped bright dots whose arrangement is in agreement with that of heptagonal and hexagonal tunnels in the structure of RNO respectively. Although Teng et al. proposed that the crystal structure of KNO might also be formed by Nb-O octahedra and contains various tunnels as RNO, they concluded that the symmetry of KNO should be lower than that of RNO. In this abstract it is reported that the crystal structure of KNO is isomorphic to that of RNO as well as that of CsxNb54(O,F)146[5].

scholarly journals Study on the Electrical, Structural, Chemical and Optical Properties of PVD Ta(N) Films Deposited with Different N2 Flow Rates

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 937
Author(s):  
Yingying Hu ◽  
Md Rasadujjaman ◽  
Yanrong Wang ◽  
Jing Zhang ◽  
Jiang Yan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Photoelectron Spectroscopy ◽  
Crystal Size ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
Flow Rates ◽  
X Ray ◽  
N2 Flow Rate

By reactive DC magnetron sputtering from a pure Ta target onto silicon substrates, Ta(N) films were prepared with different N2 flow rates of 0, 12, 17, 25, 38, and 58 sccm. The effects of N2 flow rate on the electrical properties, crystal structure, elemental composition, and optical properties of Ta(N) were studied. These properties were characterized by the four-probe method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Results show that the deposition rate decreases with an increase of N2 flows. Furthermore, as resistivity increases, the crystal size decreases, the crystal structure transitions from β-Ta to TaN(111), and finally becomes the N-rich phase Ta3N5(130, 040). Studying the optical properties, it is found that there are differences in the refractive index (n) and extinction coefficient (k) of Ta(N) with different thicknesses and different N2 flow rates, depending on the crystal size and crystal phase structure.

A Stand-Alone Mesoporous Crystal Structure Model from in situ X-ray Diffraction: Nitrogen Adsorption on 3 D Cagelike Mesoporous Silica SBA-16

2012 ◽  
Vol 18 (33) ◽  
pp. 10300-10311 ◽  
Author(s):  
Keiichi Miyasaka ◽  
Hiroko Hano ◽  
Yoshiki Kubota ◽  
Yangzheng Lin ◽  
Ryong Ryoo ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Mesoporous Silica ◽  
Nitrogen Adsorption ◽  
Structure Model ◽  
X Ray Diffraction ◽  
X Ray

SU-79: a novel germanate with 3D 10- and 11-ring channels templated by a square-planar nickel complex

2014 ◽  
Vol 1 (3) ◽  
pp. 278-283 ◽  
Author(s):  
Shiliang Huang ◽  
Jie Su ◽  
Kirsten Christensen ◽  
A. Ken Inge ◽  
Jie Liang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Nickel Complex ◽  
X Ray Diffraction ◽  
X Ray ◽  
Open Framework ◽  
Square Planar

An open-framework germanate SU-79 was synthesized using nickel complex and amine as the templates. The crystal structure was solved by the combination of rotation electron diffraction (RED) and synchrotron single crystal X-ray diffraction.

scholarly journals Crystal structure determination of karibibite, an Fe3+ arsenite, using electron diffraction tomography

2017 ◽  
Vol 81 (5) ◽  
pp. 1191-1202 ◽  
Author(s):  
Fernando Colombo ◽  
Enrico Mugnaioli ◽  
Oriol Vallcorba ◽  
Alberto García ◽  
Alejandro R. Goñi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Dft Calculations ◽  
Density Functional ◽  
Weak Interactions ◽  
Diffraction Tomography ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters

AbstractThe crystal structure of karibibite, Fe33+(As3+O2)4(As23+O5)(OH), from the Urucum mine (Minas Gerais, Brazil), was solved and refined from electron diffraction tomography data [R1 = 18.8% for F > 4σ(F)] and further confirmed by synchrotron X-ray diffraction and density functional theory (DFT) calculations. The mineral is orthorhombic, space group Pnma and unit-cell parameters (synchrotron X-ray diffraction) are a = 7.2558(3), b = 27.992(1), c = 6.5243 (3) Å, V = 1325.10(8) Å3, Z = 4. The crystal structure of karibibbite consists of bands of Fe3+O6 octahedra running along a framed by two chains of AsO3 trigonal pyramids at each side, and along c by As2O5 dimers above and below. Each band is composed of ribbons of three edge-sharing Fe3+O6 octahedra, apex-connected with other ribbons in order to form a kinked band running along a. The atoms As(2) and As(3), each showing trigonal pyramidal coordination by O, share the O(4) atom to form a dimer. In turn, dimers are connected by the O(3) atoms, defining a zig-zag chain of overall (As3+O2)n-n stoichiometry. Each ribbon of (Fe3+O6) octahedra is flanked on both edges by the (As3+O2)n-n chains. The simultaneous presence of arsenite chains and dimers is previously unknown in compounds with As3+. The lone-electron pairs (4s2) of the As(2) and As(3) atoms project into the interlayer located at y = 0 and y = ½, yielding probable weak interactions with the O atoms of the facing (AsO2) chain.The DFT calculations show that the Fe atoms have maximum spin polarization, consistent with the Fe3+ state.

scholarly journals The crystal structure of parkinsonite, nominally Pb7MoO9Cl2: a naturally occurring Aurivillius phase

2010 ◽  
Vol 74 (2) ◽  
pp. 269-275 ◽  
Author(s):  
G. O. Lepore ◽  
M. D. Welch
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
X Ray Diffraction ◽  
Aurivillius Phase ◽  
X Ray ◽  
Cell Parameters ◽  
Naturally Occurring ◽  
Final Agreement ◽  
Fourfold Axis ◽  
Synthetic Crystal

AbstractThe crystal structure of the sheet oxychloride mineral parkinsonite, nominally Pb7MoO9Cl2, has been determined for synthetic and natural crystals of analysed compositions, (Pb7.28Mo0.72) O8.96Cl1.96 and (Pb7.23Mo0.40V0.37)O8.90Cl1.82, respectively. Parkinsonite is tetragonal, space group I4/mmm. Unit-cell parameters for synthetic and natural crystals are: asynthetic = 3.9773(4) Å, csynthetic = 22.718(4) Å, Vsynthetic = 359.38(5) Å3, and anatural = 3.9570(3) Å, cnatural = 22.634(5) Å, Vnatural = 354.40(5) Å3. Final agreement indices (R1, wR2) for refinements of the two crystals are 0.024, 0.067 (synthetic) and 0.036, 0.078 (natural). Although a superlattice has been identified by electron diffraction for crystals of both samples (Welch et al., 1996), only the substructure could be determined by X-ray diffraction. This X-ray invisibility of the superstructure has also been observed for the closely related sheet oxychlorides asisite and schwartzembergite, for both of which superstructure motifs have been identified by electron diffraction. The Pb(1) site of both parkinsonite crystals is fully occupied by Pb. Refinement of the Pb content of the Pb(2) site for the synthetic and natural crystals gives occupancies of 0.85(1) and 0.70(1) respectively, corresponding to 3.40 and 2.80 Pb(2) a.p.f.u. respectively. The substituent cation Mo (synthetic crystal) and [Mo+V] (natural crystal) was located at a distance of 0.5 Å from Pb(2), being displaced along the fourfold axis. The reduced occupancy of Pb(2) is due to substitution by Mo or [Mo+V]. No evidence for separate Mo and V sites in the substructure of natural parkinsonite was found. Refined occupancies of the Cl site are 0.84(4) and 0.91(5) for the synthetic and natural crystals, respectively, and are consistent with the 9:1 superstructure component identified by electron diffraction.

scholarly journals Pengaruh Metode Sintesis Silika Mesopori SBA-15 terhadap Analisis Differential Scanning Calorimetry dan Pengukuran Low Angles X-Ray Diffraction

2018 ◽  
Vol 5 (1) ◽  
pp. 39
Author(s):  
Ridhawati Ridhawati ◽  
Abdul Wahid Wahab ◽  
Nursiah La Nafie ◽  
Indah Raya
Keyword(s):  
Crystal Structure ◽  
Differential Scanning Calorimetry ◽  
Mesoporous Silica ◽  
Crystal Size ◽  
Sol Gel ◽  
Thermal Characteristics ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Hydrothermal Methods

Mesoporous silica SBA-15 is an interesting material having highly ordered nanopores and large surface area, which is synthesized by sol gel and hydrothermal methods. In this study, mesoporous silica SBA-15 was synthesised with two different methods and the characteris was using X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). SBA-15 was prepared TEOS as precursor and Pluronic 123 as surfactant. Thermoporous mesoporous DSC thermogram results of the SBA-15A mesoporous silica is (Tg 79oC and Tc 158oC). This is relatively lower than SBA-15B (Tg 86oC and Tc 158oC). The measurement of low angle X-Ray Diffraction SBA-15A has a crystal size 9.46 nm and SBA-15B has a crystal size 9.96 nm. The synthesis of SBA-15 using the hydrothermal method needs to be studied further to obtain thermal characteristics and a more stable crystal structure

A Morophological and Crystal Structure Analysis of Particulate Rare Earth III Fluorides

1972 ◽  
Vol 30 ◽  
pp. 542-543
Author(s):  
Coy R. Morris
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Structural Analysis ◽  
Electron Diffraction ◽  
Crystal Structure Analysis ◽  
X Ray Diffraction ◽  
Structural Units ◽  
X Ray ◽  
Lower Chamber ◽  
Rare Earth Trifluorides

Previous work in this area (oftedal-1929, Zalkin and Templeton-1952 ) using X-ray diffraction techniques assigned primitive structural units to the rare earth trifluorides of Lanthanum, Cerium, Praseodymium, Neodymium, Ytterbium and Samarium.The work of greatest interest in this investigation is that of Zalkin and Templeton. In their investigation they found that the 4f trifluorides from La to Nd are hexagonal while those from Sm to Lu are orthorhombic with SmF3 exhibiting a dual structure of both units, depending on the temperature of formation.Continuing the recent work of Barr, the structures of LaF3, NdF3, PrF3, SmF3 and YbF3 were investigated using lower chamber diffraction (LCD) which produced results appearing to conflict with the X-ray work of Zalkin and Templeton. To these authors knowledge there are no known publications dealing with the structural analysis of these five rare earth trifluorides other than the two papers cited. In addition, these works deal with X-ray determinations which, although complementary to electron diffraction, lack the microanalysis and limited innerplanar spacing analysis characteristic to ED.

scholarly journals Crystal Structure of the Disordered Non-Centrosymmetric Compound Fe0.43Mo2.56SbO9.5

Crystals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 40
Author(s):  
Sk Ali ◽  
Sven Lidin ◽  
Mats Johnsson
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Building Blocks ◽  
Fold Axis ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

Single crystals of Fe0.43Mo2.56SbO9.5 were obtained by hydrothermal techniques at 230 °C. The crystal structure was determined from single crystal X-ray diffraction data. The compound crystallizes in the non-centrosymmetric space group Pc with unit cell parameters a = 4.0003(2) Å, b = 7.3355(3) Å, c = 12.6985(6) Å, β = 90°. The crystal structure comprises five crystallographically independent M atoms and one Sb3+ atom, M atoms are of two kinds of partially occupied sites Mo6+ and Fe3+. The building blocks consist of [SbO3O0.5O0.5E] octahedra (E = lone electron pair) and [(Mo/Fe)O6] octahedra. The M = (Mo, Fe) and O atoms are arranged in a distorted hexagonal 2D-net, not the Sb atoms. The distortion of the net and consequently the symmetry reduction results mainly from the location of the Sb atoms. Disorder manifests itself as a splitting of the metal sites and as a consequent shortening of the Mo–Fe distances. Six (Mo/Fe)O6 octahedra are connected to form a pseudohexagonal channel. The Sb3+ atom is displaced from the pseudo-six-fold axis.

Sign in / Sign up

Export Citation Format

Share Document