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Intermetallics or intermetallic compounds is a term that is used in a number of different ways. Most commonly it refers to solid state phases involving metals. There is a "research definition" adhered to generally in scientific publications, and a wider "common use" term. There is also a completely different use in coordination chemistry, where it has been used to refer to complexes containing two or more different metals.
Additional recommended knowledge
This was stated by Schulze in 1967,  and defines intermetallic compounds as solid phases containing two or more metallic elements, with optionally one or more non metallic elements, whose structure is distinct from that of any of the constituents. Under this definition the following are included
The definition of a metal is taken to include:
Alloys, which are a homogeneous mixture of metals, and interstitial compounds such as the carbides and nitrides are excluded under this definition. However interstitial intermetallic compounds are included as are alloys of intermetallic compounds with a metal.
In common use the research definition, including poor metals and metalloids, is extended to include compounds such as cementite, Fe3C. These compounds, sometimes termed interstitial compounds can be stoichiometric, and share similar properties to the intermetallic compounds defined above.
The term intermetallic is used  to describe compounds involving two or more metals such as the cyclopentadienyl complex Cp6Ni2Zn4.
Intermetallics involving two or more metallic elements
Intermetallic compounds are generally brittle and high melting. They often offer a compromise between ceramic and metallic properties when hardness and/or resistance to high temperatures is important enough to sacrifice some toughness and ease of processing. They can also display desirable magnetic, superconducting and chemical properties, due to their strong internal order and mixed (metallic and covalent/ionic) bonding, respectively. Intermetallics have given rise to various novel materials developments. Some examples include alnico and the hydrogen storage materials in nickel metal hydride batteries. Ni3Al, which is the hardening phase in the familiar nickel-base superalloys, and the various titanium aluminides have also attracted interest for turbine blade applications, while the latter is also used in very small quantities for grain refinement of titanium alloys.
Properties and examples
The formation of intermetallics can cause problems, Intermetallics of gold and aluminium are a significant cause of wire bond failures in semiconductor devices and other microelectronics devices. There are five of them. AuAl2 is known as "purple plague". Au5Al2 is known as "white plague".
Examples of intermetallics through history include:
German type metal is described as breaking like glass, not bending, softer than copper but more fusible than lead. . The chemical formula does not agree with the one above however the properties match with an intermetallic compound or an alloy of one.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Intermetallics". A list of authors is available in Wikipedia.|