
Binary compounds of silicon are
binary
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two values (0 and 1) for each digit
* Binary function, a function that takes two arguments
* Binary operation, a mathematical op ...
chemical compounds
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
containing
silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
and one other
chemical element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...
. Technically the term
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 ...
is reserved for any compounds containing silicon bonded to a more
electropositive
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...
element. Binary silicon compounds can be grouped into several classes.
Salt
In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
like silicides are formed with the electropositive s-block metals. Covalent silicides and silicon compounds occur with hydrogen and the elements in groups 10 to 17.
Transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...
s form metallic silicides, with the exceptions of
silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
,
gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
and the
group 12 elements. The general composition is M
nSi or MSi
n with n ranging from 1 to 6 and M standing for metal. Examples are M
5Si, M
3Si (Cu, V, Cr, Mo, Mn, Fe, Pt, U), M
2Si (Zr, Hf, Ta, Ir, Ru, Rh, Co, Ni, Ce), M
3Si
2 (Hf, Th, U), MSi (Ti, Zr, Hf, Fe, Ce, Th, Pu) and MSi
2 (Ti, V, Nb, Ta, Cr, Mo, W, Re).
The
Kopp–Neumann law applies; heat capacities are linear in the proportion of silicon:
As a general rule, nonstochiometry implies instability. These
intermetallics are in general resistant to hydrolysis, brittle, and melt at a lower temperature than the corresponding
carbide
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Interstitial / Metallic carbides
The carbides of th ...
s or
boride
A boride is a compound between boron and a less electronegative element, for example silicon boride (SiB3 and SiB6). The borides are a very large group of compounds that are generally high melting and are covalent more than ionic in nature. Some b ...
s. They are electrical conductors. However, some, such as CrSi
2, Mg
2Si, β-FeSi
2 and MnSi
1.7, are
semiconductors
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 levels ...
. Since
degenerate semiconductors exhibit some metallic properties, such as luster and electrical conductivity which decreases with temperature, some silicides classified as metals may be semiconductors.
Group 1
Silicides of
group 1 elements are saltlike silicides, except for
silane
Silane (Silicane) is an inorganic compound with chemical formula . It is a colorless, pyrophoric gas with a sharp, repulsive, pungent smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental ...
(SiH
4) whose bonds to hydrogen are covalent. Higher silane homologues are
disilane and
trisilane.
Polysilicon hydride is a two-dimensional
polymer network.
Many cluster compounds of lithium silicides are known, such as Li
13Si
4, Li
22Si
5, Li
7Si
3 and Li
12Si
7. Li
4.4Si is prepared from silicon and lithium metal in high-energy
Ball mill
A ball mill is a type of grinder filled with grinding balls, used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attri ...
process. Potential uses include electrodes in lithium batteries. Li
12Si
7 has a
Zintl phase
In chemistry, a Zintl phase is a product of a reaction between a group 1 (alkali metal) or group 2 (alkaline earth metal) and main group metal or metalloid (from groups 13, 14, 15, or 16). It is characterized by intermediate metallic/ ionic bondin ...
with planar Si
56− rings.
Li NMR spectroscopy suggests these rings are
aromatic
In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...
.
Other group 1 elements also form clusters: sodium silicide can be represented by NaSi, NaSi
2 and Na
11Si
36 and potassium silicide by K
8Si
46. Group 1 silicides are in general high melting, metallic grey, with moderate to poor electrical conductance and prepared by heating the elements. Superconducting properties have been reported for Ba
8Si
46. Several silicon
Zintl ions (, , ) are known with group 1 counterions.
Group 2
Silicides of
group 2 elements are also saltlike silicides except for
beryllium
Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...
whose phase diagram with silicon is a simple eutectic (1085 °C @ 60% by weight silicon). Again there is variation in composition:
magnesium silicide
Magnesium silicide, Mg2Si, is an inorganic compound consisting of magnesium and silicon. As-grown Mg2Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators.
Cr ...
is represented by Mg
2Si,
calcium silicide can be represented by Ca
2Si, CaSi, CaSi
2, Ca
5Si
3 and by Ca
14Si
19, strontium silicide can be represented by Sr
2Si, SrSi
2 and Sr
5Si
3 and barium silicide can be represented by Ba
2Si, BaSi
2, Ba
5Si
3 and Ba
3Si
4. Mg
2Si, and its
solid solution
A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...
s with Mg
2Ge and Mg
2Sn, are good
thermoelectric materials and their
figure of merit
A figure of merit (FOM) is a performance metric that characterizes the performance of a device, system, or method, relative to its alternatives. Examples
*Absolute alcohol content per currency unit in an alcoholic beverage
*accurizing, Accuracy o ...
values are comparable with those of established materials.
Transition and inner transition metals
The
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...
s form a wide range of silicon
intermetallics with at least one binary crystalline phase. Some exceptions exist.
Gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
forms a
eutectic at 363 °C with 2.3% silicon by weight (18% atom percent) without mutual solubility in the solid state.
Silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
forms another eutectic at 835 °C with 11% silicon by weight, again with negligible mutual solid state solubility. In
group 12 all elements form a eutectic close to the metal melting point without mutual solid-state solubility: zinc at 419 °C and > 99 atom percent zinc and cadmium at 320 °C (< 99% Cd).
Commercially relevant intermetallics are
group 6 Group 6 may refer to:
* Group 6 element, chemical element classification
* Group 6 (motorsport), FIA classification for sports car racing
* Group 6 Rugby League, rugby league competition in New South Wales, Australia
{{disambig ...
molybdenum disilicide, a commercial ceramic mostly used as an heating element.
Tungsten disilicide is also a commercially available ceramic with uses in microelectronics.
Platinum silicide
Platinum silicide, also known as platinum monosilicide, is the inorganic compound with the formula PtSi. It is a semiconductor that turns into a superconductor when cooled to 0.8 K.
Structure and bonding
The crystal structure of PtSi is orthorho ...
is a semiconductor material.
Ferrosilicon
Ferrosilicon is an ferroalloy, alloy of iron and silicon. It has a typical silicon content of 15–90% by weight and a high proportion of iron silicides.
Production and reactions
Ferrosilicon is produced by reduction of silica or sand with coke ...
is an iron alloy that also contains some calcium and aluminium.
MnSi, known as
brownleeite, can be found in outer space. Several Mn silicides form a
Nowotny phase. Nanowires based on silicon and manganese can be synthesised from Mn(CO)
5SiCl
3 forming nanowires based on Mn
19Si
33. or grown on a silicon surface MnSi
1.73 was investigated as
thermoelectric material and as an optoelectronic thin film. Single-crystal MnSi
1.73 can form from a tin-lead melt
In the frontiers of technological research, iron disilicide is becoming more and more relevant to
optoelectronics
Optoelectronics (or optronics) is the study and application of electronic devices and systems that find, detect and control light, usually considered a sub-field of photonics. In this context, ''light'' often includes invisible forms of radi ...
, specially in its crystalline form β-FeSi
2. They are used as thin films or as nanoparticles, obtained by means of epitaxial growth on a silicon substrate.
Group 13
In
group 13 boron (a
metalloid
A metalloid is a chemical element which has a preponderance of material property, properties in between, or that are a mixture of, those of metals and Nonmetal (chemistry), nonmetals. The word metalloid comes from the Latin language, Latin ''meta ...
) forms several binary crystalline
silicon boride compounds: SiB
3, SiB
6, SiB
n. With
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
, a
post-transition metal
The metallic elements in the periodic table located between the transition metals to their left and the chemically weak nonmetallic metalloids to their right have received many names in the literature, such as post-transition metals, poor metal ...
, a eutectic is formed (577 °C @ 12.2 atom % Al) with maximum solubility of silicon in solid aluminium of 1.5%. Commercially relevant
aluminium alloy
An aluminium alloy ( UK/IUPAC) or aluminum alloy ( NA; see spelling differences) is an alloy in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin, nickel and zinc. There ...
s containing silicon have at least element added.
Gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875,
elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
, also a
post-transition metal
The metallic elements in the periodic table located between the transition metals to their left and the chemically weak nonmetallic metalloids to their right have received many names in the literature, such as post-transition metals, poor metal ...
, forms a eutectic at 29 °C with 99.99% Ga without mutual solid-state solubility;
indium
Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...
and thallium behave similarly.
Group 14
Silicon carbide
Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A wide bandgap semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder a ...
(SiC) is widely used as a ceramic or example in car brakes and bulletproof vests. It is also used in semiconductor electronics. It is manufactured from
silicon dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...
and carbon in an
Acheson furnace between 1600 and 2500 °C. There are 250 known crystalline forms with alpha silicon carbide the most common. Silicon itself is an important semiconductor material used in microchips. It is produced commercially from
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...
and
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
at 1900 °C and crystallizes in a diamond cubic crystal structure.
Germanium silicide forms a
solid solution
A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...
and is again a commercially used semiconductor material. The
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 ...
–silicon phase diagram is a eutectic and the
lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
–silicon phase diagram shows a
monotectic transition and a small eutectic transition but no solid solubility.
Group 15
Silicon nitride
Silicon nitride is a chemical compound of the elements silicon and nitrogen. (''Trisilicon tetranitride'') is the most thermodynamically stable and commercially important of the silicon nitrides, and the term ″''Silicon nitride''″ commonly re ...
(Si
3N
4) is a ceramic with many commercial high-temperature applications such as engine parts. It can be synthesized from the elements at temperatures between 1300 and 1400 °C. Three different crystallographic forms exist. Other binary silicon nitrogen compounds have been proposed (SiN, Si
2N
3, Si
3N) and other SiN compounds have been investigated at cryogenic temperatures (SiN
2, Si(N
2)
2, SiNNSi).
Silicon tetraazide is an unstable compound that easily detonates.
The phase diagram with
phosphorus
Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
shows SiP and SiP
2. A reported silicon phosphide is Si
12P
5 (no practical applications), formed by
annealing an amorphous Si-P alloy.
The
arsenic
Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...
–silicon phase diagram measured at 40 Bar has two phases: SiAs and SiAs
2. The
antimony
Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...
–silicon system comprises a single eutectic close to the melting point of Sb. The
bismuth
Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...
system is a monotectic.
Group 16
In group 16
silicon dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...
is a very common compound that widely occurs as sand or quartz. SiO
2 is tetrahedral with each silicon atom surrounded by 4 oxygen atoms. Numerous crystalline forms exist with the tetrahedra linked to form a polymeric chain. Examples are
tridymite
Tridymite is a high-temperature polymorphism (materials science), polymorph of silica and usually occurs as minute tabular white or colorless pseudo-hexagonal crystals, or scales, in cavities in felsic volcanic rocks. Its chemical formula is sili ...
and
cristobalite
Cristobalite ( ) is a mineral polymorph of silica that is formed at very high temperatures. It has the same chemical formula as quartz, Si O2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members o ...
. A less common oxide is
silicon monoxide
Silicon monoxide is the chemical compound with the formula SiO where silicon is present in the oxidation state +2. In the vapour phase, it is a diatomic molecule.
It has been detected in stellar objects and has been described as the most common o ...
that can be found in outer space. Unconfirmed reports exist for nonequilibrium Si
2O, Si
3O
2, Si
3O
4, Si
2O
3 and Si
3O
5.
Silicon sulfide
Silicon disulfide is the inorganic compound with the formula Silicon, SiSulfur, S2. Like silicon dioxide, this material is polymeric, but it adopts a 1-dimensional structure quite different from the usual polymorphism (materials science), forms o ...
is also a chain compound. Cyclic SiS
2 has been reported to exist in the gas phase. The phase diagram of silicon with
selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
has two phases: SiSe
2 and SiSe. Tellurium silicide is a semiconductor with formula TeSi
2 or Te
2Si
3.
Group 17
Binary silicon compounds in group 17 are stable compounds ranging from gaseous
silicon fluoride (SiF
4) to the liquids
silicon chloride (SiCl
4 and
silicon bromide SiBr
4) to the solid
silicon iodide (SiI
4). The
molecular geometry
Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that det ...
in these compounds is tetrahedral and the bonding mode covalent. Other known stable fluorides in this group are Si
2F
6, Si
3F
8 (liquid) and polymeric solids known as
polysilicon fluorides (SiF
2)
x and (SiF)
x. The other halides form similar binary silicon compounds.
[''Inorganic chemistry'', Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman 2001]
The periodic table of the binary silicon compounds
References
{{Chemical compounds by element
Binary compounds
Silicon compounds
Silicon, binary compounds