Improved structural model of Pb-doped γ-Bi2O3: (Bi23.68Pb0.32)(Bi1.28Pb0.72)O38.48

2012 ◽  
Vol 27 (1) ◽  
pp. 2-7 ◽  
Author(s):  
Aleksandra Dapčević ◽  
Dejan Poleti ◽  
Ljiljana Karanović
Keyword(s):  
Single Phase ◽  
Structural Model ◽  
Nominal Composition ◽  
Structural Constraints ◽  
Powder Diffraction Data ◽  
Cell Content ◽  
Single Phase Sample ◽  
X Ray ◽  
Cation Sites ◽  
Oxide Ions

A polycrystalline single-phase sample with nominal composition Bi24PbO37 was synthesized from Bi2O3 and PbO by a high-temperature solid state reaction at 690 °C for 1.5 h. The compound adopts Bi12SiO20-type structure [cubic, space group I23 (No. 197); a = 10.24957(3) Å] and was refined to Rp = 7.96%, Rwp = 10.4%, Rexp = 8.43%, RB = 3.06%, and S = 1.23. The distributions of Pb2+ and Bi3+ over cationic sites based on the X-ray powder diffraction data were determined using a combination of the Rietveld refinement and bond valence calculations. The results showed that the asymmetric unit contains two mixed cation sites: the fully occupied 24f site and the partly occupied 8c site, with the unit-cell content (Bi23.68Pb0.32)(Bi1.28Pb0.72)O38.48. The structural constraints favor a preference of Pb2+ ion for the 8c site, i.e. only 1.3% of Bi3+ is substituted by Pb2+ at the 24f site and 36% at the 8c site. At the 24f site, the cations are surrounded by 5 + 2 or in a very small amount by 5 + 1 + 2 oxide ions, forming a base bicapped square pyramid or a bicapped highly deformed octahedron, respectively. At the 8c site, the cations with three oxide ions form a trigonal pyramid with the cations at the apex.

scholarly journals Mn-Induced Thermal Stability of L10 Phase in Fept Magnetic Nanoscale Ribbons

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1278
Author(s):  
Alina Daniela Crisan ◽  
Aurel Leca ◽  
Dan Pantelica ◽  
Ioan Dan ◽  
Ovidiu Crisan
Keyword(s):  
Rare Earth ◽  
Single Phase ◽  
Permanent Magnets ◽  
Magnetic Hysteresis ◽  
Ternary Alloys ◽  
Large Temperature ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Operation Conditions

Magnetic nanoscale materials exhibiting the L10 tetragonal phase such as FePt or ternary alloys derived from FePt show most promising magnetic properties as a novel class of rare earth free permanent magnets with high operating temperature. A granular alloy derived from binary FePt with low Pt content and the addition of Mn with the nominal composition Fe57Mn8Pt35 has been synthesized in the shape of melt-spun ribbons and subsequently annealed at 600 °C and 700 °C for promoting the formation of single phase, L10 tetragonal, hard magnetic phase. Proton-induced X-ray emission spectroscopy PIXE has been utilized for checking the compositional effect of Mn addition. Structural properties were analyzed using X-ray diffraction and diffractograms were analyzed using full profile Rietveld-type analysis with MAUD (Materials Analysis Using Diffraction) software. By using temperature-dependent synchrotron X-ray diffraction, the disorder–order phase transformation and the stability of the hard magnetic L10 phase were monitored over a large temperature range (50–800 °C). A large interval of structural stability of the L10 phase was observed and this stability was interpreted in terms of higher ordering of the L10 phase promoted by the Mn addition. It was moreover found that both crystal growth and unit cell expansion are inhibited, up to the highest temperature investigated (800 °C), proving thus that the Mn addition stabilizes the formed L10 structure further. Magnetic hysteresis loops confirmed structural data, revealing a strong coercive field for a sample wherein single phase, hard, magnetic tetragonal L10 exists. These findings open good perspectives for use as nanocomposite, rare earth free magnets, working in extreme operation conditions.

Synthesis and Magnetic Properties of La-Doped Ni Ferrites

2010 ◽  
Vol 148-149 ◽  
pp. 736-739
Author(s):  
Ju Hua Luo
Keyword(s):  
Single Phase ◽  
Raw Materials ◽  
Nominal Composition ◽  
Vibrating Sample Magnetometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnetic Parameters ◽  
Ft Ir ◽  
Mechanochemical Treatments ◽  
La Doped

Ni ferrites doped with lanthanum with a nominal composition of NiFe2-xLaxO4(x=0.05) were obtained by mechanochemical treatments using NiCO3•2Ni (OH)2•4H2O , La2O3 and Fe2O3 as raw materials. Both series of materials were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM). The results indicated that the mixture became amorphous stage after ball-milled for 30 h, and single phase NiFe1.95La0.05O4 could be obtained after calcined at 700 for 2 h. The addition of lanthanum resulted in a reduction of all the magnetic parameters evaluated.

scholarly journals Structural Chemistry of Some Phases in The YC-Ni-B System

1994 ◽  
Vol 376 ◽  
Author(s):  
B. C. Chakoumakos
Keyword(s):  
Powder Diffraction ◽  
Single Phase ◽  
Rietveld Analysis ◽  
Neutron Powder Diffraction ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Arc Melting ◽  
Phase Pure

ABSTRACTNiB, monoclinic Ni4B3, Ni2B and Ni3B were prepared by arc-melting and their roomtemperature crystal structures were refined by Rietveld analysis of neutron powder diffraction data. The NiB refinement is altogether new data. Although the B atoms in NiB form characteristic zigzag chains, the primary coordination of each atom by atoms of the other kind is similar and distinctively sevenfold, with one short (2.117 Å), two intermediate (2.152 Å), and four long (2.163 Å) bonds. Other samples with stoichiometries (YC)nNi2B2, n = 3, 4, did not yield single-phase material, but both x-ray and neutron powder diffraction suggest that the n = 4 structure is present in both of these samples. Phase-pure samples of these homologues may require non-stoichiometry and a more controlled thermal history than is attainable by arc melting.

Powder Diffraction Data for ZnGa2S4

1990 ◽  
Vol 5 (4) ◽  
pp. 223-224 ◽  
Author(s):  
Charlotte K. Lowe-Ma
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Tetragonal Unit Cell ◽  
Group I ◽  
Cation Sites

AbstractObserved and calculated X-ray powder diffraction data are reported for ZnGa2S4. After corrections to the observed data, refined tetragonal unit cell parameters ao= 5.2779(2), co= 10.4179(8) Å (λ = 1.54051 Å) were obtained. The powder pattern for ZnGa2S4was calculated in space group Iwith a stoichiometric amount of Zn and Ga randomly distributed amongst the two cation sites.

AgScO2 Revisited: Synthesis, Crystal Structure Refinement and Properties of the Single-phase 3R Polymorph

2011 ◽  
Vol 66 (3) ◽  
pp. 227-229 ◽  
Author(s):  
Volker Dietrich ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Activation Energy ◽  
Stainless Steel ◽  
Single Phase ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Ordered Structure ◽  
Powder Diffraction Data ◽  
X Ray ◽  
High Oxygen Pressure

Silver scandium oxide AgScO2 has been obtained from Ag2O and Sc2O3 by solid-state reaction at elevated temperature and under high oxygen pressure in stainless-steel autoclaves. AgScO2 was obtained in the 3R Delafossite-type structure, R¯3m, with a = 3.21092(2), c = 18.5398(1) Å and Z = 3, containing virtually no admixtures of the 2H polytype. The fully ordered structure was solved by high-resolution X-ray powder diffraction data, R(F2) = 0.0436, 30 parameters. AgScO2 decomposes at around 740 ºC into Ag and Sc2O3 with the release of oxygen. The conductivity of AgScO2 increases gradually with temperature from 5.79 × 10−18 to 7.94 × 10−10 S cm−1, and is ionic in nature, the activation energy for ion conduction being 75 kJ mol−1 in the temperature range from 250 to 425 ºC.

Tungusite: new data, relationship with gyrolite and structural model

1995 ◽  
Vol 59 (396) ◽  
pp. 535-543 ◽  
Author(s):  
Giovanni Ferraris ◽  
Alessandro Pavese ◽  
Svetlana V. Soboleva
Keyword(s):  
Solid Solution ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structural Model ◽  
Substitutional Solid Solution ◽  
Chemical Analyses ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Tetrahedral Layer ◽  
The Ideal

AbstractNew chemical analyses, electron and X-ray powder diffraction data, and comparison with gyrolite and reyerite show that tungusite has the ideal formula , symmetry P and a = 9.714(9), b = 9.721(9), c = 22.09(3), α = 90.13(1)°, β = 98.3(2)°, γ = 120.0(1)°, Z = 1. A structural model for tungusite is derived by splitting the double tetrahedral layer of reyerite and inserting a trioctahedral X sheet which is ideally occupied by Fe2+. Polytypism phenomena due to different relative positions between tetrahedral and X sheets are discussed. A substitutional solid solution represented by the formula [Ca14(OH)8]Si24−yAlyO60[NaxM9−(x+z)□z(OH)14−(x+y+2z)·(x+y+2z)H2O] includes tungusite (x = y = z = 0, M = Fe2+ and gyrolite (x = 1, y = 1, z = 6, M = Ca).

scholarly journals Structural position and oxidation state of nickel in SrTiO3

2013 ◽  
Vol 03 (04) ◽  
pp. 1350031 ◽  
Author(s):  
Irina A. Sluchinskaya ◽  
Alexander I. Lebedev ◽  
Alexei Erko
Keyword(s):  
Solid Solution ◽  
Oxidation State ◽  
Single Phase ◽  
Photovoltaic Effect ◽  
X Ray Diffraction ◽  
Spectra Analysis ◽  
Single Phase Sample ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Preparation Conditions

The properties of Ni -doped strontium titanate are studied using X-ray diffraction and XAFS spectroscopy. It is shown that regardless of the preparation conditions, the SrTi 1-x Ni x O 3 solid solution and the NiTiO 3 phase are the most stable phases which can coexist. According to the EXAFS data, in the single-phase sample of SrTi 0.97 Ni 0.03 O 3, the Ni atoms substitute for the Ti ones and are on-center. The distortion of the oxygen octahedra is not observed. The XANES spectra analysis shows that the oxidation state of nickel in NiTiO 3 is 2+, and in the SrTi 1-x Ni x O 3 solid solution it is close to 4+. It is shown that the strongest light absorption in doped samples is associated with the presence of tetravalent nickel in the SrTi 1-x Ni x O 3 solid solution. This doping seems the most promising one for solar energy converters that exploit the bulk photovoltaic effect.

Simultaneous determination of several crystal structures from powder mixtures: the combination of powder X-ray diffraction, band-target entropy minimization and Rietveld methods

2014 ◽  
Vol 47 (2) ◽  
pp. 659-667 ◽  
Author(s):  
Martin Schreyer ◽  
Liangfeng Guo ◽  
Satyanarayana Thirunahari ◽  
Feng Gao ◽  
Marc Garland
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Single Phase ◽  
Materials Science ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Present Contribution ◽  
X Ray ◽  
Indexing Structure

Crystal structure determination is the key to a detailed understanding of crystalline materials and their properties. This requires either single crystals or high-quality single-phase powder X-ray diffraction data. The present contribution demonstrates a novel method to reconstruct single-phase powder diffraction data from diffraction patterns of mixtures of several components and subsequently to determine the individual crystal structures. The new method does not require recourse to any database of known materials but relies purely on numerical separation of the mixture data into individual component diffractograms. The resulting diffractograms can subsequently be treated like single-phase powder diffraction data,i.e.indexing, structure solution and Rietveld refinement. This development opens up a host of new opportunities in materials science and related areas. For example, crystal structures can now be determined at much earlier stages when only impure samples or polymorphic mixtures are available.

SUPERCONDUCTIVITY IN THE U-Y-Ba-Cu-O SYSTEM

1987 ◽  
Vol 01 (07n08) ◽  
pp. 323-326 ◽  
Author(s):  
Q.Z. QIN ◽  
A.D. HE ◽  
W.J. JIA ◽  
L.D. MA ◽  
Z.Y. HUA
Keyword(s):  
Single Phase ◽  
Ambient Pressure ◽  
Raw Material ◽  
Material Structure ◽  
Nominal Composition ◽  
Uranium Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zero Resistance ◽  
Superconducting Oxides

High Tc superconductivity has been observed in a new U-Y-Ba-Cu-O system at ambient pressure. The zero-resistance temperature in the sample with nominal composition of U0.1Y1.1Ba0.8CuO4−δ is 87K with a width of 2K. X-ray diffraction analysis shows that none of the peaks could be fitted to the uranium oxides and the other raw material structure, and its pattern might be attributed to new multiple phases with structure different from the known single-phase superconducting oxides.

X-Ray Powder Diffraction Data for Tetragonal Zirconia Solid Solutions in System ZrO2-YTaO4

1992 ◽  
Vol 7 (3) ◽  
pp. 174-175 ◽  
Author(s):  
Dae-Joon Kim ◽  
Camden R. Hubbard
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Single Phase ◽  
Tetragonal Zirconia ◽  
Phase Region ◽  
Solid Solution Series ◽  
Powder Diffraction Data ◽  
Monoclinic Structure ◽  
X Ray ◽  
End Members

AbstractTetragonal zirconia (t- ZrCO2) can be stabilized with 15 to 22 mol% YTaO4. X-ray powder diffraction data for the end members of the solid solution series Zr0.76Y0.12Ta0.12O2 and Zr0.66Y0.17Ta0.17O2 are reported along with lattice parameters across the single phase region. These tetragonal zirconias are characterized by large tetragonalities (c/ √ 2a > 1.0203) and nontransformability to the monoclinic structure.

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