The A15 phases
(also known as β-W
structure types) are series of intermetallic compounds
with the chemical formula A
(where A is a transition metal
and B can be any element
) and a specific structure. Many of these compounds have superconductivity
at around 20 K
(−424 °F), which is comparatively high, and remain superconductive in magnetic fields of tens of teslas
(hundreds of kilogauss
). This kind of superconductivity (Type-II superconductivity
) is an important area of study as it has several practical applications.
The all materials in the A15 phase are very brittle which makes machining difficult for those materials.
The structure of the A<sub>3</sub>B is based on a bcc structure of B. It has one lattice point in the centre of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell. Two atoms A are located on the each cube face is bisectedby orthogonal Nb chains
The first time the A15 structure was observed in 1931 when a electrolytically deposited layer of tungsten
was examined. The discussion if the β–tungsten structure is an allotrope of tungsten or a the structure of a tungsten suboxide was long-standing and in 1998 still articles about the discussion were published. In the end it seems most... Read More