Ternary transition metal gallides with TiNiSi, ZrBeSi and MgZn2-type structure

2019 ◽  
Vol 74 (3) ◽  
pp. 297-306 ◽  
Author(s):  
Lukas Heletta ◽  
Theresa Block ◽  
Steffen Klenner ◽  
Rainer Pöttgen
Keyword(s):  
Transition Metal ◽  
Powder Diffraction ◽  
Metallic Iron ◽  
Site Occupancy ◽  
Laves Phase ◽  
Structural Motif ◽  
Equiatomic Composition ◽  
Laves Phases ◽  
X Ray ◽  
Arc Melting

AbstractA series of ternary transition metal gallides around the equiatomic composition have been synthesized from the elements by arc-melting and subsequent annealing. The compounds crystallize with site occupancy variants of the hexagonal Laves phase MgZn2, with the hexagonal ZrBeSi or the orthorhombic TiNiSi type. All samples have been characterized on the basis of their lattice parameters, determined by X-ray powder diffraction (Guinier technique). The structures of NbCr1.58Ga0.42 and NbFe1.51Ga0.49 (MgZn2 type, P63/mmc), NbRhGa (ZrBeSi type, P63/mmc), and ScNiGa, ScPtGa and ScAuGa (TiNiSi type, Pnma) were refined from single crystal X-ray diffractometer data. The ScPtGa and ScAuGa crystals showed trilling formation. Mixed site occupancies were only observed in the Laves phases while all other crystals were well ordered. A striking structural motif of NbRhGa is the formation of niobium chains (264 pm Nb–Nb) along the c axis. Several gallides were magnetically characterized. They are Pauli paramagnets. The two crystallographically independent iron sites in the Laves phase TaFeGa could be distinguished in the 57Fe Mössbauer spectrum. The isomer shifts of 0.06(3) (Fe1) and –0.02(3) (Fe2) mm s−1 indicate metallic iron.

Rare Earth-Transition Metal Indides with Lu5Ni2In4-type Structure

2008 ◽  
Vol 63 (12) ◽  
pp. 1447-1449 ◽  
Author(s):  
Roman Zaremba ◽  
Wilfried Hermes ◽  
Matthias Eul ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Transition Metal ◽  
Powder Diffraction ◽  
Magnetic Moment ◽  
Magnetic Moments ◽  
Type Structure ◽  
Induction Melting ◽  
X Ray ◽  
Arc Melting ◽  
Experimental Magnetic Moment

New intermetallic compounds RE5T2In4 (RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu; T = Rh, Ir) were synthesized by arc-melting of the elements or by induction melting of the elements in tantalum crucibles under flowing argon. The samples were characterized by X-ray powder diffraction. They crystallize with the orthorhombic Lu5Ni2In4-type structure, space group Pbam, Z = 2, a 2 : 1 intergrowth variant of CsCl and AlB2 related slabs of compositions InRE8 (distorted cubes) and RhRE6 (distorted trigonal prisms). Susceptibility measurements of Ce5Ir2In4 have revealed modified Curie- Weiss behavior above 70 K with an experimental magnetic moment of 2.45(1) μB / Ce atom. The cerium magnetic moments order ferri- or ferromagnetically at TC = 7.1(2) K.

ALCHEMI of NbCr2/V C15-structured laves phase

1996 ◽  
Vol 54 ◽  
pp. 554-555
Author(s):  
P.G. Kotula ◽  
I.M. Anderson ◽  
F. Chu ◽  
T.E. Mitchell ◽  
J. Bentley
Keyword(s):  
First Principles ◽  
Laves Phase ◽  
Physical Metallurgy ◽  
Ion Milling ◽  
Laves Phases ◽  
X Ray ◽  
Arc Melting ◽  
Quantum Detector ◽  
Defect Mechanism ◽  
Structure Calculations

Laves-phase intermetallics are of potential interest for use as high temperature structural materials, of which NbCr2-based C15-structured Laves phases are particularly attractive. Vanadium-alloyed NbCr2 Laves phases have been studied. The defect mechanism of a ternary Laves phase is crucial to understanding its physical metallurgy and deformation behavior. It is suggested based on the Nb-Cr-V phase diagram and first-principles total energy and electronic structure calculations for NbCr2 that V should occupy the B sites in C15-structured AB2. In this paper, ALCHEMI is employed to examine this assumption for one composition of a V-alloyed NbCr2 Cl5 Laves phase.A Nb-Cr-V alloy of composition Nb33Cr42V25 was prepared by arc-melting followed by annealing at 1400°C for 120 h. Specimens were prepared for microanalysis by cutting 3 mm discs followed by dimpling and ion milling. Energy-dispersive X-ray (EDX) spectra were acquired with a Philips CM30 operating at 300 kV and equipped with a Kevex Quantum detector. Fourteen spectra were collected near <014> over a range of {400} excitations between symmetry and beyond {12 0 0}.

Synthesis and characterisation of transition metal substituted barium hollandite ceramics

2006 ◽  
Vol 932 ◽  
Author(s):  
Neil C. Hyatt ◽  
Martin C. Stennett ◽  
Steven G. Fiddy ◽  
Jayne S. Wellings ◽  
Sian S. Dutton ◽  
...  
Keyword(s):  
Transition Metal ◽  
Oxidation State ◽  
Powder Diffraction ◽  
Single Phase ◽  
Maximum Density ◽  
Processing Conditions ◽  
Metal Oxidation ◽  
Exafs Data ◽  
X Ray ◽  
Oxygen Atoms

ABSTRACTA range of transition metal bearing hollandite phases, formulated Ba1.2B1.2Ti6.8O16 (B2+ = Mg, Co, Ni, Zn, Mn) and Ba1.2B2.4Ti5.6O16 (B3+ = Al, Cr, Fe) were prepared using an alkoxide - nitrate route. X-ray powder diffraction demonstrated the synthesis of single phase materials for all compositions except B = Mn. The processing conditions required to produce > 95 % dense ceramics were determined for all compositions, except B = Mg for which the maximum density obtained was > 93 %. Analysis of transition metal K-edge XANES data confirmed the presence of the targeted transition metal oxidation state for all compositions except B = Mn, where the overall oxidation state was found to be Mn3+. The K-edge EXAFS data of Ba1.2B1.2Ti6.8O16 (B = Ni and Co) were successfully analysed using a crystallographic model of the hollandite structure, with six oxygen atoms present in the first co-ordination shell at a distance of ca. 2.02Å. Analysis of Fe K-edge EXAFS data of Ba1.2B2.4Ti5.4O16 revealed a reduced co-ordination shell of five oxygens at ca. 1.99Å.

scholarly journals Effect of Nd, Pr substitutional atoms on the magnetic and magnetostrictive properties in (Tb-Dy)(Fe-Co)2 Laves phases

2021 ◽  
Vol 2103 (1) ◽  
pp. 012196
Author(s):  
G A Politova ◽  
M A Ganin ◽  
A B Mikhailova ◽  
D A Morozov ◽  
K E Pankov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Magnetic Properties ◽  
Laves Phase ◽  
Type Structure ◽  
Partial Substitution ◽  
Laves Phases ◽  
Temperature Range ◽  
Homogenizing Annealing ◽  
Arc Melting ◽  
Magnetostrictive Materials

Abstract Polycrystalline TbxDy1-xR0.1Fe2-zCoz (R = Nd, Pr, x = 0.2, 0.3; z = 0, 1.3) cubic Laves phase alloys with MgCu2-type structure were prepared by arc melting followed by homogenizing annealing. The crystal structure, magnetic properties, and magnetostriction have been investigated. Compounds with high values of magnetostrictive susceptibility were found in the temperature range 150-300 K. Compounds with partial substitution of cobalt for iron demonstrate a change in the sign of anisotropic magnetostriction. This work continues the search for magnetostrictive materials with inexpensive neodymium and praseodymium.

Synthesis, Structure, and Characterization of La1−xBax (0 ≤ x ≤ 1)

1992 ◽  
Vol 271 ◽  
Author(s):  
Joseph E. Sunstrom ◽  
Susan M. Kauzlarich
Keyword(s):  
Magnetic Susceptibility ◽  
Powder Diffraction ◽  
Single Phase ◽  
Gravimetric Analysis ◽  
Thermal Gravimetric ◽  
Temperature Dependent ◽  
X Ray ◽  
Early Transition Metal ◽  
Arc Melting

ABSTRACTThe compounds La1−xBaxTiO3 (0 ≤ × ≤ 1) have been prepared by arc melting stoichiometric amounts of LaTiO3 and BaTiO3. Single phase samples can be made for the entire stoichiometry range. The polycrystalline samples have been characterized by thermal gravimetric analysis, X-ray powder diffraction, and temperature dependent magnetic susceptibility. This series of compounds has been studied as a possible candidate for an early transition metal superconductor.

X-ray powder diffraction data of CoSi

1997 ◽  
Vol 12 (4) ◽  
pp. 252-254 ◽  
Author(s):  
G. Ghosh ◽  
G. V. Narasimha Rao ◽  
V. S. Sastry ◽  
A. Bharathi ◽  
Y. Hariharan ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Melting Process ◽  
Lattice Parameter ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray ◽  
Structure Space ◽  
Arc Melting ◽  
Cubic Structure

X-ray powder diffraction data of CoSi are reported. The sample was prepared by an arc melting process and has a cubic structure (space group P213, space group No. 198) with lattice parameter a=4.4427 Å, Dx=6.591 gcm−3, Z=4, and I/Ic=1.03.

The X-Ray Powder Diffraction Patterns and Crystal Structure for Al2M3Y(M=Cu, Ni)

2014 ◽  
Vol 950 ◽  
pp. 48-52
Author(s):  
De Gui Li ◽  
Ming Qin ◽  
Liu Qing Liang ◽  
Zhao Lu ◽  
Shu Hui Liu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Hexagonal Structure ◽  
Argon Atmosphere ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Arc Melting ◽  
Diffraction Patterns

The Al2M3Y(M=Cu, Ni) compound was synthesized by arc melting under argon atmosphere. The high-quality powder X-ray diffraction data of Al2M3Y have been presented. The refinement of the X-ray diffraction patterns for the Al2M3Y compound show that the Al2M3Y has hexagonal structure, space groupP6/mmm(No.191), with a = b = 5.1618(2) Å, c = 4.1434(1) Å,V= 95.6 Å3,Z= 1,ڑx= 5.7922 g/cm3,F30= 155.5(0.0057, 34), RIR = 2.31 for Al2Cu3Y, and with a = b = 5.0399(1) Å, c = 4.0726(1) Å,V= 89.59 Å3,Z= 1,ڑx= 5.9118 g/cm3,F30= 135.7(0.0072, 30), RIR = 2.54 for Al2Ni3Y.

X-ray powder diffraction study of K2MSiO4, M=Mg, Zn, Co, Cd

1996 ◽  
Vol 11 (1) ◽  
pp. 51-55 ◽  
Author(s):  
W. A. Dollase
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Site Occupancy ◽  
Cubic Phase ◽  
Variable Degree ◽  
Cubic Symmetry ◽  
X Ray ◽  
Constrained Model ◽  
Diffraction Patterns

The title materials are stuffed cristobalites possessing moderate to extreme pseudosymmetry. On the bases of their X-ray powder diffraction patterns, the Mg, Zn, and Cd compounds had been previously reported as cubic and, more recently, the Zn phase as orthorhombic. Newly measured X-ray powder diffraction data demonstrate that all (including the hitherto unknown Co analog) have the Pca21 structure of Na2BeSiO4 at room temperature, but with a widely variable degree of cubic pseudosymmetry. Observed X-ray diffraction data are in good agreement with those calculated by the Rietveld method using a constrained model with Pca21 M2+/Si site occupancy and pseudocentrosymmetric Pcab atom locations. For the most nearly cubic phase, the Cd compound, there is too little deviation in the pattern from cubic symmetry to support atom coordinate refinement even with the constrained model. In these derivatives of the stuffed cristobalite structure family, M2+ and Si atoms form an ordered tetrahedral array which avoids M2+–O–M2+ connections. Potassium atoms fill all of the intervening large cavity sites.

scholarly journals Pressing the Limits of Rietveld Refinement

1988 ◽  
Vol 41 (2) ◽  
pp. 297 ◽  
Author(s):  
RA Young
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Site Occupancy ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Refinement Method

Two examples are given, one with X-ray data and one with netltron data, of the determination of structural detail which appear to be at the edge of current possibility for the Rietveld structure-refinement method. In the first example, 2�2 wt% Sb substituted in CalO(P04)6F2 was located. X-ray powder diffraction data collected with special attention to intensity precision and scale constancy were used. The problem was solved through comparison of intra-sample site-occupancy ratios between Sb-doped and undoped samples. In the second example, high quality, high resolution neutron powder diffraction data were required. The problem was to distinguish between two subtly different models of kaolinite for which the R-weighted-pattern values differed only by 2 or 3 units in the third digit and, particularly, to understand the basis for the consistent programmatic choice of one of the models (PI) over the other. The answer was found in the calculated and 'observed' intensities for (h+ k)-odd reflections; although they were very small, less than 1% of the intensities of the main reflections, many of them were distinctly nonzero. Even though these reflections were not separately observable, because of overlap and small size, they nonetheless correlated with one model sufficiently better than the other to produce the consistent choice.

Orientation Relationships in the System Nb-NbCr2

1997 ◽  
Vol 3 (S2) ◽  
pp. 707-708
Author(s):  
P. G. Kotula ◽  
K. C. Chen ◽  
D. J. Thoma ◽  
F. Chu ◽  
T. E. Mitchell
Keyword(s):  
Microstructural Characterization ◽  
Laves Phase ◽  
Orientation Relationships ◽  
Ion Milling ◽  
Two Phase ◽  
Laves Phases ◽  
Arc Melting ◽  
Transmission Electron ◽  
Structural Applications ◽  
Two Phases

Laves-phase intermetallics are of potential use as high-temperature structural materials. NbCr2-based C15-structured alloys are of particular interest for such applications. by themselves, Laves phases generally have poor ductility and fracture toughness at low temperatures. Two phase alloys (i.e., Laves phase and the ductile bcc phase) are considered more promising for structural applications. The orientation relationships between the two phases can contribute to the mechanical behavior of the material. In this study, observations of two different orientation relationships in a Nb-NbCr2 eutectic are discussed and compared with previous studies of the NbCr2 system, as well as the TiCr2 system.A Nb-NbCr2 eutectic alloy was prepared by arc-melting high-purity alloys followed by annealing at 1400°C for 100 h and then cooling at l°C/min. The complete details of the materials preparation have been given elsewhere. Specimens were prepared for observation in the transmission electron microscope (TEM) by cutting 3 mm discs with a coring saw, followed by dimpling and ion milling. Microstructural characterization was performed with a Philips CM30 TEM operating at 300 kV.

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