A pyrosilicate is a type of

chemical compound 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 ele ...

; either an

ionic compound In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ...

that contains the pyrosilicate anion , or an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the

hexavalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...

≡-O-≡ group. The anion is also called disilicate"Disilicate"
''Chemspider'' website, CSID:5257009, Accessed 2018-05-26 or diorthosilicate. Ionic pyrosilicates can be considered

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively ...

of the unstable pyrosilicic acid, . Unlike the acid, the salts can be stable. Indeed, pyrosilicates occur widely in nature as a class of

silicate minerals Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually cons ...

, specifically the sorosilicates. Some notable synthetic pyrosilicates include * sodium pyrosilicate , a possible component of water glass. *

sodium iron(II) pyrosilicate Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

, a potential

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction i ...

material for

batteries Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

.Abhishek Panigrahi, Shin-ichi Nishimura, Tatau Shimada, Eriko Watanabe, Wenwen Zhao, Gosuke Oyama, and Atsuo Yamada (2017): "Sodium Iron(II) Pyrosilicate : A Potential Cathode Material in the -- System". ''Chemistry of Materials'', volume 29, issue 10, pages 4361–4366. * sodium manganese(II) pyrosilicate , another potential

material.Viktor Renman, Mario Valvo, Cheuk-Wai Tai, and Cesar Pay Gómez (2017): "Manganese Pyrosilicates as Novel Positive Electrode Materials for Na-Ion Batteries". Uppsala University Publications, DIV
urn:nbn:se:uu:diva-334063
/ref>Viktor Renman (2017): "Structural and Electrochemical Relations in Electrode Materials for Rechargeable Batteries", Doctoral Thesis, Uppsala University, Department of Chemistry. ORCID: 0000-0001-8739-4054

Structure

The pyrosilicate anion can be described as two

tetrahedra In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ...

that share a vertex (an

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

atom). The vertices that are not shared carry a negative charge each. The structure of solid sodium pyrosilicate was described by

Volker Kahlenberg Volker may refer to: * Volker (name), including a list of people with the given name or surname * Volker, Kansas City, a historic neighborhood in Kansas City * Volker Boulevard, Kansas City * ''Alien Nations'' (German: ''Die Völker''), a real-time ...

and others in 2010.Volker Kahlenberg, Thomas Langreiter, and Erik Arroyabe (2010): " – The Missing Structural Link among Alkali Pyrosilicates". ''Zeitschrift für anorganishe und allgemeine Chemie'' (''Journal for Inorganic and General Chemistry''), volume 636, issue 11, pages 1974-1979. Yuri Smolin and

Yuri Shepelev Yuri may refer to: People and fictional characters Given name *Yuri (Slavic name), the Slavic masculine form of the given name George, including a list of people with the given name Yuri, Yury, etc. *Yuri (Japanese name), also Yūri, feminine Jap ...

determined in 1970 the crystal structures of pyrosilicates of

rare earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides ( yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous si ...

s with generic formula , where "Ln" stands for either one of lanthanum,

cerium Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 o ...

neodymium Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishes ...

, samarium,

europium Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...

gadolinium Gadolinium is a chemical element with the symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with atmospheric oxygen o ...

, dysprosium,

holmium Holmium is a chemical element with the symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series. It is a relatively soft, silvery, fairly corrosion-resistant and malleable metal. Like a lot of ...

yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a " rare-earth element". Yttrium is almost always found in c ...

, erbium,

thulium Thulium is a chemical element with the symbol Tm and atomic number 69. It is the thirteenth and third-last element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other c ...

, or

ytterbium Ytterbium is a chemical element with the symbol Yb and atomic number 70. It is a metal, the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the othe ...

. They were found to belong to four distinct

crystallographic Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wo ...

classes, determined by the size of the

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

.Yu. I. Smolin and Yu. F. Shepelev (1970): "The crystal structures of the rare earth pyrosilicates". ''Acta Crystallographica Section B'', volume B26, pages 484-492. Other researchers also studied yttrium pyrosilicate .,Dias, H.W.; Glasser, F.P.; Gunwardane, R.P.; and Howie, R.A. (1990): "The crystal structure of δ-yttrium pyrosilicate, δ-". ''Zeitschrift für Kristallographie'', volume 191, issues 1/2, pages 117-123; ISSN 0044-2968

gadolinium pyrosilicate Gadolinium is a chemical element with the symbol Gd and atomic number 64. Gadolinium is a silvery-white metal when oxidation is removed. It is only slightly malleable and is a ductile rare-earth element. Gadolinium reacts with atmospheric oxyge ...

., and

scandium pyrosilicate Thortveitite is a rare mineral consisting of scandium yttrium silicate (Sc,Y)2Si2O7. It is the primary source of scandium. Occurrence is in granitic pegmatites. It was named after Olaus Thortveit, a Norwegian engineer. It is grayish-green, black ...

.Anan'eva, G.V.; Karapetyan, V.E.; Korovkin, A.M.; Merkulyaeva, T.I.; Peschanskaya, I.A.; Savinova, I.P.; and Feofilov, P.P. (1982): "Strukturnye kharakteristiki i fizicheskie svojstva kristallov diorto(piro)silikatov lantanoidov, ittriya i skandiya, vyrashchennykh metodom Chokhral'skogo" ("Structural characteristics and physical properties of diortho(pyro)silicate crystals of lanthanides yttrium and scandium grown by the Czochralski technique"). ''Izv. Akad. Nauk SSSR, Neorg. Mater'' (translated in ''Inorganic Materials'', USA) volume 18, issue 3, pages 442-445. ISSN 0002-337X.

Preparation

Rare earth pyrosilicates can be obtained by fusing the corresponding oxide with silica in 1:2 molar ratio, Single crystals can be grown by the

Verneuil process The Verneuil method (or Verneuil process or Verneuil technique), also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1883 by the French chemist Auguste Verneuil. It is ...

or the

Czochralski method The Czochralski method, also Czochralski technique or Czochralski process, is a method of crystal growth used to obtain single crystals of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, platinum, silver, ...

References

{{reflist Oxyanions Sorosilicates