Atom order and thermodynamic properties of the ternary Laves phase Ti(TiyNixAl1–x–y)2
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Andriy Grytsiv
Abstract
Combined refinement of neutron powder, X-ray single crystal and powder diffraction data allows precise evaluation of symmetry and atom site occupation for the MgZn2-type Laves phase. For compositions Ti(Ni1–x,Alx)2 titanium atoms were found to fully occupy the 4f site, whilst Ni- and Al-atoms randomly share the 2a and 6h sub-lattice sites of space group P63/mmc. At higher Ti-concentrations, Ti-atoms tend to enter the 2a and 6h site. Compositional dependences of the site occupations were used to explain the curved shape of the homogeneity region of the Laves phase. Investigation of the phase relations around the Ti-rich side of the ternary Laves phase was based on LOM, EPMA and X-ray diffraction experiments on argon arc-melted bulk alloys, which were annealed at 1000 °C in vacuum-sealed silica capsules for 100 h. The Ti-rich end of the homogeneity region of the ternary Laves phase at 1000 °C was derived from EMPA to be at Ti0.463Ni0.273Al0.264. Heat of formation data, derived from adiabatic drop calorimetry, were Δ298H0 = –57.9 ± 3.5 kJ/mol for Ti0.34Ni0.18Al0.48and –61.6 ± 3.3 kJ/mol for Ti0.36Ni0.24Al0.40. For the ab initio density functional theory applications a large number of structural models were investigated in order to calculate the concentration dependent heats of formation, structural stabilities, lattice parameters, bulk moduli and site occupancies, which are in good agreement with experiment. The theoretical analysis revealed that there are no Ni—Ni nearest neighbours when the concentration of Ni is smaller than that of Al. With increasing Al concentration, Al starts to fill 2a sites, and then continues occupying 6h sites. In compounds with Ti concentration larger than 33.3 at% the 4f sites are fully occupied by Ti, and the excessive Ti prefers 6h sites. The Al concentration of the Al-rich end of the homogeneity region of the ternary Laves phase was predicted to be 57 at%.
© by Oldenbourg Wissenschaftsverlag, München
Artikel in diesem Heft
- Editorial: Crystal Chemistry of Intermetallic Compounds
- Fritz H. Laves – 100 years young
- Fritz H. Laves – an ideal for generations
- Gustav E. R. Schulze's pioneering work on Laves phases
- Preparation, phase stability and structure of the C36 Laves phase Nb1–xCo2+x
- Atom order and thermodynamic properties of the ternary Laves phase Ti(TiyNixAl1–x–y)2
- Atomic ordering in the Laves phases L1 V(Co1–xSix)2 (x = 0.43 and 0.56)
- Microscopic structures of Laves phases and structurally related compounds: a transmission electron microscopy study
- Binary rare earth Laves phases — an overview
- Binary intermetallic phases formed by Ca, Sr, Ba, Eu and Yb: similarities and differences
- Complexity of hexagonal approximants in the RE13Zn~58 system (RE = Ce, Pr, Nd, Sm, Gd, Tb and Dy)
- Reflections on symmetry and formation of axial quasicrystals
- Mosaic-like tilings derivated from o-Co4Al13 and m-Co4Al13 crystal structures
- High-pressure crystal chemistry of binary intermetallic compounds
- Re3B type intermetallics — crystal chemistry, bonding and properties
- Ti2Rh6B – a new boride with a double perovskite-like structure containing octahedral Rh6 clusters
- On the formation and crystal structure of the Pd6B phase
- Crystal growth and magnetic properties of rare earth borosilicides
- The effect of transition metal doping on thermal conductivity of YB66
- Structure refinements of iron borides Fe2B and FeB
- Cubic structure types of rare-earth intermetallics and related compounds
- Structural variations in Gd5Si4-xSnx: size vs. electronic effects
- Tin flux synthesis of rare-earth metal silicide compounds RESi1.7 (RE = Dy, Ho): a novel ordered structure derived from the AlB2 type
- Filling the CoSn host-cell: the HfFe6Ge6-type and the related structures
- Synthesis and characterization of Na2Ba4Ga2Sb6 and Li13Ba8GaSb12
- Ge40.0Te5.3I8: synthesis, crystal structure, and properties of a new clathrate-I compound
- Ag6GeS4X2 (X: Cl, Br): surprisingly no filled Laves phases but the first representatives of a new structure type
- Low- and high-temperature structures of YbCuBi
- (La3Zx)Al and (Ce3Zx)Al with Z = C, N, O: preparation, physical properties and chemical bonding of metal-rich perovskites
- Geometric variations and electron localizations in intermetallics: PbFCl type compounds
- A novel series of sphere packings with arbitrarily low density
- Books Received
Artikel in diesem Heft
- Editorial: Crystal Chemistry of Intermetallic Compounds
- Fritz H. Laves – 100 years young
- Fritz H. Laves – an ideal for generations
- Gustav E. R. Schulze's pioneering work on Laves phases
- Preparation, phase stability and structure of the C36 Laves phase Nb1–xCo2+x
- Atom order and thermodynamic properties of the ternary Laves phase Ti(TiyNixAl1–x–y)2
- Atomic ordering in the Laves phases L1 V(Co1–xSix)2 (x = 0.43 and 0.56)
- Microscopic structures of Laves phases and structurally related compounds: a transmission electron microscopy study
- Binary rare earth Laves phases — an overview
- Binary intermetallic phases formed by Ca, Sr, Ba, Eu and Yb: similarities and differences
- Complexity of hexagonal approximants in the RE13Zn~58 system (RE = Ce, Pr, Nd, Sm, Gd, Tb and Dy)
- Reflections on symmetry and formation of axial quasicrystals
- Mosaic-like tilings derivated from o-Co4Al13 and m-Co4Al13 crystal structures
- High-pressure crystal chemistry of binary intermetallic compounds
- Re3B type intermetallics — crystal chemistry, bonding and properties
- Ti2Rh6B – a new boride with a double perovskite-like structure containing octahedral Rh6 clusters
- On the formation and crystal structure of the Pd6B phase
- Crystal growth and magnetic properties of rare earth borosilicides
- The effect of transition metal doping on thermal conductivity of YB66
- Structure refinements of iron borides Fe2B and FeB
- Cubic structure types of rare-earth intermetallics and related compounds
- Structural variations in Gd5Si4-xSnx: size vs. electronic effects
- Tin flux synthesis of rare-earth metal silicide compounds RESi1.7 (RE = Dy, Ho): a novel ordered structure derived from the AlB2 type
- Filling the CoSn host-cell: the HfFe6Ge6-type and the related structures
- Synthesis and characterization of Na2Ba4Ga2Sb6 and Li13Ba8GaSb12
- Ge40.0Te5.3I8: synthesis, crystal structure, and properties of a new clathrate-I compound
- Ag6GeS4X2 (X: Cl, Br): surprisingly no filled Laves phases but the first representatives of a new structure type
- Low- and high-temperature structures of YbCuBi
- (La3Zx)Al and (Ce3Zx)Al with Z = C, N, O: preparation, physical properties and chemical bonding of metal-rich perovskites
- Geometric variations and electron localizations in intermetallics: PbFCl type compounds
- A novel series of sphere packings with arbitrarily low density
- Books Received
