Intermetallic compounds, binary

As in ionic compounds, the atoms in a binary intermetallic compound show a tendency, albeit less pronounced, to be surrounded by atoms of the other kind as far as possible. However, it is not possible to fulfill this condition simultaneously for both kinds of atoms if they form a closest-packed arrangement. For compositions MXn with n < 3 it cannot be fulfilled for either the M or the X atoms in every case every atom has to have some adjacent atoms of the same kind. Only with a higher content of X atoms, beginning with MX3 (n > 3), are atomic arrangements possible in which every M atom is surrounded solely by X atoms the X atoms, however, must continue to have other X atoms as neighbors. 

E. R. Petty, Hot Hardness and Other Properties of Some Binary Intermetallic Compounds of Aluminum, Jour. Inst. Metals, 89,343 (1960-61). 

These relationships have been used to predict the existence and/or the structure type (and the unit cell characteristics) of binary intermetallic compounds. 

A selection of frequent stoichiometries and common structural types found within the binary intermetallic compounds of the alkali metals is given in Table 5.6. 

Kim S-J (2007) Substitution effects in binary intermetallic compounds investigations in the system alkali and alkaline-earth metal - tin and alkaline-earth metal - bismuth. PhD Thesis, Technische Universitat Miinchen, Miinchen... 

Around 1928, Zintl had begun to investigate binary intermetallic compounds, in which one component is a rather electropositive element, e.g., an alkali- or an alkaline earth metal [1,2]. Zintl discovered that in cases for which the Hume-Rothery rules for metals do not hold, significant volume contractions are observed on compound formation, which can be traced back to contractions of the electropositive atoms [2]. He explained this by an electron transfer from the electropositive to the electronegative atoms. For example, the structure of NaTl [3] can easily be understood using the ionic formulation Na Tl" where the poly- or Zintl anion [TF] forms a diamond-like partial structure - one of the preferred structures, for a four electron species [1,2], Zintl has defined a class of compounds, which, in the beginning, was a somewhat curious link between well-known valence compounds and somehow odd intermetallic phases. 

Information on binary intermetallic compounds of Sn and Li is summarized in refs. 1 and 2. The existence of Li Sn, LijSnj and Li2Sn5 is indicated by thermal, X-ray" and microscopic analysis. Thermal and thermoresistometric analyses yield phase diagrams showing LiSn ( S326°C), LiSn (mp 485°C), Li Sn ( 502°C), LijSnj (<720°C), Li Sna (mp 783°C), and Li4Sn (mp 765°C). The alloys are melted in iron crucibles in an Ar atmosphere. A phase corresponding to Li22Sn5 also exists . 

Binary intermetallic compounds of the light actinides display a wide variety of magnetic and electronic properties that are not well understood. Physical phenomena associated with... 

This section on intermetallic compounds is organized in two parts. First we will discuss the results obtained for binary intermetallic compounds. Subsequently, the large group of ternary intermetallics will be dealt with. This last section comprises the results obtained on the large family of the well-known Heusler alloys. 

Kerr rotation crystal structure, the lattice constants (nm), the room-temperature magnetization o300 (Am2/kg). Data are taken from the review by Buschow et al. (1983a). 

It is also interesting to note that the decomposition of pseudobinary intermetallic compounds (LaNi4Fe and CeNis-jCo ) leads to the formation of bimetallic transition metal particles which display different selectivities than the catalysts derived from the related binary intermetallic compound (Paul-Boncour et al. 1991, France and Wallace 1988). The characterization of the bimetallic particles by XRD, Mossbauer spectroscopy and magnetism indicated that their composition was close to that of the starting alloy. 

A great number of the ternary and binary intermetallic compounds can be considered as members of linear homogeneous and inhomogeneous structure series. The classification of the linear series eind their members using numeric symbols and onedimensional symmetry groups will be made in this section. 

Given any two transition metals, use their Miedema parameters to derive the existence of binary intermetallic compounds. 

Nitrogen is a gas in its precursors, N2, NH3, N2H4, but nitrogen atoms can behave as metal atoms when they are bonded in binary intermetallic compounds. Metal nitrides behave like intermetallic compounds being brittle and good electron conductors and having remarkable stoichiometries. 

Demchyna R, Leoni S, Rosner H, Schwarz U (2006) High-pressure crystal chemistry of binary intermetallic compounds. Z Krist 221 420-434... 

The number of binary intermetallic compounds of rare earths for which the crystal structures have been determined is about 1800 and this number will increase in the future. In the early years of these studies the simplest structures were resolved and only the more complex structures await complete determinations. 

Four binary intermetallic compounds are of interest in the Ti-Al system - Ti3Al (ct2), TiAl (y), TiAl2, andTiAlg (Fig. 6-20). There are also two ternary intermetallic phases of... 

At AnXa stoichiometry there are four families of binary intermetallic compounds, which represent different stacking schemes of the close-packed layer shown in Fig. 19.6(a) [34]. All stacking variants yield crystal structures in which a CN 12 polyhedron consists entirely of X atoms surrounding the An atom. The structures that occur are the AuCus, TiNis, MgCdj, and PuAls types. The AuCus-type structure, ordered fee, is the most prevalent, occurring particularly when the actinides combine with Rh and Pd the other three structure types are ordered variants of the hep structure. 

Kuz ma et al. (1986a) and Lomnitskaya and Kuz ma (1991a) showed that phosphorus behaves as a metallic element in ternary M-M -P systems at low P content (up to 25 at.%), as indicated by the formation of phosphorus solid solutions in binary intermetallic compounds (e.g., Zr2pe, Zr2Co). In ternary compounds phosphorus atoms occupy the same positions as iron triad metals in the structure. At phosphorus contents up to 33.3 at.%, metallic-type chemical bonds occur in the compounds, and there are no P-P contacts. 

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