scholarly journals Structure of the quaternary alloy Zn0.6Mn0.4In2S4from synchrotron powder diffraction and electron transmission microscopy

2006 ◽  
Vol 39 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Rosario Ávila-Godoy ◽  
Asiloé J. Mora ◽  
Dwight R. Acosta-Najarro ◽  
Gerzon E. Delgado ◽  
Santos A. López-Rivera ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Parent Compound ◽  
Quaternary Alloy ◽  
X Ray Diffraction ◽  
Transmission Microscopy ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Synchrotron Powder Diffraction

The aim of the present work was to determine the structure of the quaternary alloy Zn0.6Mn0.4In2S4and to locate the Mn2+. This was accomplished by means of powder synchrotron X-ray diffraction, high-resolution microscopy and convergent-beam electron diffraction (CBED). The powder X-ray diffraction pattern was indexed in a rhombohedral cell, with cell constantsa= 3.875 (2),c= 37.208 (4) Å, and possible space groupsR\bar{3}morR3m. Rietveld refinements using different cationic arrangements in these space groups were performed. A model in space groupR3m, in which the tetrahedral and octahedral sites were occupied by different proportions of Zn, Mn and In atoms, gave the best result. The Rietveld refinement of this model led to figures of meritRwp= 9.8%,Rp= 9.1% and χ2= 11.1. Selected-area electron diffraction patterns and high-resolution transmission electron micrographs along [001] reveal the rhombohedral configuration. CBED patterns perpendicular to [001], showing the distinctive 3msymmetry, confirmed space groupR3mand the breaking of the centrosymmetry of the parent compound, ZnIn2S4.

scholarly journals Disorder in a natural ixiolite: high resolution studies at 293 K and 120 K.

2014 ◽  
Vol 70 (a1) ◽  
pp. C1092-C1092
Author(s):  
Leandro Almeida ◽  
Douglas Miquita ◽  
Bernardo Rodrigues
Keyword(s):  
High Resolution ◽  
General Formula ◽  
Diffraction Data ◽  
High Mobility ◽  
Structure Type ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Independent Observations

Grice, Ferguson and Hawthorne [1] describes the ixiolite of Bernic Lake, Manitoba, Canada. According to these authors, the ixiolite is part of the Ixiolite-Tantalite-Wodgnite system and crystallizes in space group Pbcn, with general formula MO2, in a α-PbO2structure type. The structure of the mineral ixiolite from Volta Grande pegmatite, in Brazil, is herein described from high resolution (0.5 Å) X-ray diffraction data using MoKα radiation. This mineral has formula MO2, with M = Fe, Mn, Nb or Ta. Data were collected at 293 K and at 120 K from a well formed crystal (0.6 x 0.4 x 0.3 mm). 49868 and 32294 reflections were collected at 293 K and at 120 K, respectively. The structure of the ixiolite was well solved in both temperatures: at 293 K the mineral crystalizes in the space group Cmcm, and the structure was refined to R(F2)=0.0476, from 728 independent reflections. At 120 K, the mineral crystalizes in space group Pbcn, and the structure was refined to R(F2)= 0.0537 from 1357 independent observations. It is interesting to notice that the different space groups of the herein described ixiolite at 120 K (Pbcn) and at 293 K (Cmcm) is related to the different occupations of oxygen sites, as expected from the high mobility of oxygen atoms.

Electron diffraction study of the space group of Bi5Ti3FeO15 multiferroic ceramic

2020 ◽  
Vol 76 (5) ◽  
pp. 454-457
Author(s):  
Ying Zheng ◽  
Xinyan Wu ◽  
Yongcheng Zhang ◽  
Weiquan Shao ◽  
Wanneng Ye
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Electron Diffraction Study ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Phase Compound ◽  
First Time

Bi5Ti3FeO15 (pentabismuth trititanium iron pentadecaoxide), which is a multiferroic four-layer Aurivillius phase compound, has received much attention in recent years. However, three mutually inconsistent orthorhombic space groups, i.e. A21 am, Fmm2 and Pnn2, have been reported for the room-temperature phase of Bi5Ti3FeO15 by X-ray and neutron diffraction investigations. Here, electron diffraction results are presented and discussed for the first time to unambiguously clarify the room-temperature space group of ceramic Bi5Ti3FeO15. It has been found that all the observed reflections from the ceramic agree with those expected in A21 am, while the observed reflections 011, 013 and 015 should be forbidden in the case of Fmm2, and no 107 and 109 reflections were observed although allowed for Pnn2. The present study has demonstrated that the space group of Bi5Ti3FeO15 ceramic is A21 am rather than Fmm2 or Pnn2, an identification that proved to be a challenge for X-ray diffraction. On the basis of the space group A21 am, the lattice parameters of the Bi5Ti3FeO15 ceramic were calculated from its X-ray diffraction data.

Determination of crystal symmetry for Bi4Ti3O12-based ferroelectrics by using electron diffraction

2013 ◽  
Vol 46 (3) ◽  
pp. 798-800 ◽  
Author(s):  
Wanneng Ye ◽  
Chaojing Lu ◽  
Peng You ◽  
Kun Liang ◽  
Yichun Zhou
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Electron Diffraction Technique ◽  
Convergent Beam

In recent years, inconsistent space groups of monoclinicB1a1 and orthorhombicB2cbhave been reported for the room-temperature ferroelectric phases of both Bi4Ti3O12and lanthanide-substituted Bi4Ti3O12. In this article, the electron diffraction technique is employed to unambiguously clarify the crystal symmetries of ferroelectric Bi4Ti3O12and Bi3.15Nd0.85Ti3O12single crystals at room temperature. All the reflections observed from the two crystals match well with those derived fromB1a1, but the observed reflections 010, 030, {\overline 2}10 and {\overline 2}30 should be forbidden in the case ofB2cb. This fact indicates that both the ferroelectrics are of the space groupB1a1 rather thanB2cb, which is confirmed by convergent-beam electron diffraction observations. On the basis of the monoclinic space groupB1a1, the lattice parameters of both the ferroelectrics were calculated by the Rietveld refinement of powder X-ray diffraction data.

Microstructure and crystal symmetry of Pb2Sr2(Y/Ca)Cu3O9−δ

1990 ◽  
Vol 48 (4) ◽  
pp. 64-65
Author(s):  
Y. P. Lin ◽  
J. S. Xue ◽  
J. E. Greedan
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Carbon Film ◽  
Basic Structure ◽  
Crystal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
New Family ◽  
Convergent Beam

A new family of high temperature superconductors based on Pb2Sr2YCu3O9−δ has recently been reported. One method of improving Tc has been to replace Y partially with Ca. Although the basic structure of this type of superconductors is known, the detailed structure is still unclear, and various space groups has been proposed. In our work, crystals of Pb2Sr2YCu3O9−δ with dimensions up to 1 × 1 × 0.25.mm and with Tc of 84 K have been grown and their superconducting properties described. The defects and crystal symmetry have been investigated using electron microscopy performed on crushed crystals supported on a holey carbon film.Electron diffraction confirmed x-ray diffraction results which showed that the crystals are primitive orthorhombic with a=0.5383, b=0.5423 and c=1.5765 nm. Convergent Beam Electron Diffraction (CBED) patterns for the and axes are shown in Figs. 1 and 2 respectively.

scholarly journals Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

2000 ◽  
Vol 5 (S1) ◽  
pp. 97-103
Author(s):  
Kathleen A. Dunn ◽  
Susan E. Babcock ◽  
Donald S. Stone ◽  
Richard J. Matyi ◽  
Ling Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
The Third ◽  
Dislocation Arrangement ◽  
Image Position ◽  
Gan Film

Diffraction-contrast TEM, focused probe electron diffraction, and high-resolution X-ray diffraction were used to characterize the dislocation arrangements in a 16µm thick coalesced GaN film grown by MOVPE LEO. As is commonly observed, the threading dislocations that are duplicated from the template above the window bend toward (0001). At the coalescence plane they bend back to lie along [0001] and thread to the surface. In addition, three other sets of dislocations were observed. The first set consists of a wall of parallel dislocations lying in the coalescence plane and nearly parallel to the substrate, with Burgers vector (b) in the (0001) plane. The second set is comprised of rectangular loops with b = 1/3 [110] (perpendicular to the coalescence boundary) which originate in the coalescence boundary and extend laterally into the film on the (100). The third set of dislocations threads laterally through the film along the [100] bar axis with 1/3<110>-type Burgers vectors These sets result in a dislocation density of ∼109 cm−2. High resolution X-ray reciprocal space maps indicate wing tilt of ∼0.5º.

The structures of marialite (Me6) and meionite (Me93) in space groups P42/n and I4/m, and the absence of phase transitions in the scapolite series

2011 ◽  
Vol 26 (2) ◽  
pp. 119-125 ◽  
Author(s):  
Sytle M. Antao ◽  
Ishmael Hassan
Keyword(s):  
Phase Transitions ◽  
High Resolution ◽  
Crystal Structures ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Space Groups ◽  
Cell Parameters ◽  
The Mean

The crystal structures of marialite (Me6) from Badakhshan, Afghanistan and meionite (Me93) from Mt. Vesuvius, Italy were obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Their structures were refined in space groups I4/m and P42/n, and similar results were obtained. The Me6 sample has a formula Ca0.24Na3.37K0.24[Al3.16Si8.84O24]Cl0.84(CO3)0.15, and its unit-cell parameters are a=12.047555(7), c=7.563210(6) Å, and V=1097.751(1) Å3. The average ⟨T1-O⟩ distances are 1.599(1) Å in I4/m and 1.600(2) Å in P42/n, indicating that the T1 site contains only Si atoms. In P42/n, the average distances of ⟨T2-O⟩=1.655(2) and ⟨T3-O⟩=1.664(2) Å are distinct and are not equal to each other. However, the mean ⟨T2,3-O⟩=1.659(2) Å in P42/n and is identical to the ⟨T2′-O⟩=1.659(1) Å in I4/m. The ⟨M-O⟩ [7]=2.754(1) Å (M site is coordinated to seven framework O atoms) and M-A=2.914(1) Å; these distances are identical in both space groups. The Me93 sample has a formula of Na0.29Ca3.76[Al5.54Si6.46O24]Cl0.05(SO4)0.02(CO3)0.93, and its unit-cell parameters are a=12.19882(1), c=7.576954(8) Å, and V=1127.535(2) Å3. A similar examination of the Me93 sample also shows that both space groups give similar results; however, the C–O distance is more reasonable in P42/n than in I4/m. Refining the scapolite structure near Me0 or Me100 in I4/m forces the T2 and T3 sites (both with multiplicity 8 in P42/n) to be equivalent and form the T2′ site (with multiplicity 16 in I4/m), but ⟨T2-O⟩ is not equal to ⟨T3-O⟩ in P42/n. Using different space groups for different regions across the series implies phase transitions, which do not occur in the scapolite series.

Effects of Phosphorus Exposure on Arsenic-Stabilized GaAs 2×4 Surface

1993 ◽  
Vol 312 ◽  
Author(s):  
A. H. Bensaoula ◽  
A. Freundlich ◽  
A. Bensaoula ◽  
V. Rossignol
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Growth Process ◽  
High Energy ◽  
Ex Situ ◽  
Chemical Beam Epitaxy ◽  
High Energy Electron ◽  
X Ray Diffraction ◽  
X Ray

AbstractPhosphorus exposed GaAs (100) surfaces during a Chemical Beam Epitaxy growth process are studied using in-situ Reflection High Energy Electron Diffraction and ex-situ High Resolution X-ray Diffraction. It is shown that the phosphorus exposure of a GaAs (100) surface in the 500 – 580 °C temperature range results in the formation of one GaP monolayer.

Metal-selenolate chemistry: stereochemistry of adamantane-type clusters of formula [(μ-SePh)6(MSePh)4]2− (M = Zn and Cd)

1992 ◽  
Vol 70 (3) ◽  
pp. 792-801 ◽  
Author(s):  
Jagadese J. Vittal ◽  
Philip A. W. Dean ◽  
Nicholas C. Payne
Keyword(s):  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Bridging Ligands ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
X Ray Crystallography ◽  
Cell Dimensions ◽  
Minimum Number

The structures of three tetramethylammonium salts containing anions of formula [(μ-SePh)6(MSePh)4]2− (M = Zn and Cd) were determined by single crystal X-ray diffraction techniques. The Zn salt crystallizes in different space groups depending upon the solvent combination used in the synthesis. Thus crystals of (Me4N)2[Zn4(SePh)10], 1, grown from a mixture of methanol, acetonitrile, and acetone are triclinic, space group [Formula: see text] with cell dimensions a = 13.214(2), b = 23.859(2), c = 13.072(1) Å, α = 91.134(8), β = 113.350(8), γ = 79.865(9)°, and Z = 2. In the absence of acetone, a solvated crystal (Me4N)2[Zn4(SePh)10]•CH3CN, 2, is formed, which belongs to the monoclinic space group P21/n with a = 14.248(1), b = 39.722(2), c = 13.408(1) Å, β = 97.132(5)°, and Z = 4. The Cd salt (Me4N)2[Cd4(SePh)10], 3, crystallizes in the monoclinic space group P21/c, with a = 20.830(2), b = 14.282(1), c = 25.872(1) Å, β = 99.626(6)°, and Z = 4. These three salts are the first examples of homoleptic, tetranuclear selenolatometal(II) anions with (μ-Se)6M4 cages of adamantane-type stereochemistry. In each case the phenyl substituents of the bridging ligands adopt the configuration [aae, aae, aee, aee], which has the minimum number of two 1,3-axial–axial non-bonding substituent interactions. Keywords: selenolate complexes, synthesis, X-ray crystallography, isomerism, adamantane stereochemistry.

Structure of fluorite-like compound based on Nd5Mo3O16with lead partly substituting for neodymium

2015 ◽  
Vol 71 (2) ◽  
pp. 186-193 ◽  
Author(s):  
Alexander M. Antipin ◽  
Natalia I. Sorokina ◽  
Olga A. Alekseeva ◽  
Alexandra N. Kuskova ◽  
Elena P. Kharitonova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Single Crystal ◽  
Experimental Verification ◽  
X Ray Diffraction ◽  
Transmission Microscopy ◽  
X Ray ◽  
Oxygen Ion ◽  
First Time ◽  
Edx Microanalysis

A single crystal of Nd5Mo3O16with lead partly substituting for neodymium, which has a fluorite-like structure, was studied by precision X-ray diffraction, high-resolution transmission microscopy and EDX microanalysis. The crystal structure is determined in the space group Pn\bar 3n. It was found that the Pb atoms substitute in part for Nd atoms in the structure and are located in the vicinity of Nd2 positions. Partial substitutions of Mo cations for Nd positions and of Nd for Mo positions in crystals of theLn5Mo3O16oxide family are corroborated by X-ray diffraction for the first time. The first experimental verification of the location of an additional oxygen ion in the voids abutting MoO4tetrahedra was obtained.

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