Manganese disilicide (MnSi₂) is an

intermetallic compound An intermetallic (also called intermetallic compound, intermetallic alloy, ordered intermetallic alloy, long-range-ordered alloy) is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic elements. Inte ...

, a

silicide A silicide is a type of chemical compound that combines silicon and a usually more electropositive element. Silicon is more electropositive than carbon. In terms of their physical properties, silicides are structurally closer to borides than t ...

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

. It is a

non-stoichiometric compound Non-stoichiometric compounds are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula); most often, in s ...

, with a silicon deficiency expressed as MnSi_2–x. Crystal structures of many MnSi_2–x compounds resemble a chimney ladder and are called

Nowotny phase In inorganic chemistry, a Nowotny chimney ladder phase (NCL phase) is a particular intermetallic crystal structure found with certain binary compounds. NLC phases are generally tetragonal and are composed of two separate sublattices. The first is ...

s. They include MnSi₂ (x=0), Mn₄Si₇ (x=0.250), Mn₁₁Si₁₉ (x=0.273), Mn₁₅Si₂₆ (x=0.267) and Mn₂₇Si₄₇ (x=0.259). These phases have very similar

unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector In mathematics, a unit vector i ...

s whose length varies from 1.75 nm for MnSi₂ or Mn₄Si₇, which have almost the same structures, to 11.8 nm for Mn₂₇Si₄₇. Mn4Si7 structure

MnSi_2–x Nowotny phases have a Mn sublattice with a β-

tin Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the ...

structure overlaid with a

face-centered cubic In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties o ...

Si sublattice. They resemble chimneys of transition metal atoms containing spiraling ladders of Si. These phases are

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

s with a

band gap In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to t ...

of 0.4 to 0.9 eV. They exhibit a reasonably high thermoelectric figure of merit ZT ~ 0.8 and have potential applications in

thermoelectric generator A thermoelectric generator (TEG), also called a Seebeck generator, is a solid state device that converts heat (driven by temperature differences) directly into electrical energy through a phenomenon called the '' Seebeck effect'' (a form of the ...

References

{{Silicides Manganese compounds Transition metal silicides