# Pechini process

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{{Short description|Chemical Process}}
The '''Pechini process''' or '''liquid mix process''' as proposed in 1967 is a technique of depositing dielectric films of titanates and niobates of lead and alkaline-earth elements in the production of capacitors. Later, the process was customised for the in-lab synthesis of multicomponent finely dispersed oxide materials.<ref>{{cite web|last=|first=|date=|title=Pechini method|url=https://eng.thesaurus.rusnano.com/wiki/article2075#:~:text=The%20Pechini%20method%20was%20proposed,multicomponent%20finely%20dispersed%20oxide%20materials|access-date=|website=|publisher=|quote=}}</ref><ref>{{cite journal|author=A.M.Huízar-Félix|last2=T.Hernández|last3=S.de la Parra |last4=J.Ibarra|last5=B.Kharisov|year=2012|title=Sol–gel based Pechini method synthesis and characterization of Sm1 − xCaxFeO3 perovskite 0.1 ≤ x ≤ 0.5|journal=Powder Technology|volume=229|issn=0032-5910|pages=290–293|doi=10.1016/j.powtec.2012.06.057}}</ref> It is named after its American inventor, Maggio Pechini.

== Description ==
It is related to the [sol-gel](/source/sol-gel) route. An aqueous solution of suitable oxides or salts is mixed with an [alpha hydroxycarboxylic acid](/source/alpha_hydroxycarboxylic_acid) such as [citric acid](/source/citric_acid). [Chelation](/source/Chelation) takes place in the solution. A [polyhydroxy alcohol](/source/Sugar_alcohol) is then added, and the liquid is heated to 150–250&nbsp;°C (300–480&nbsp;°F) to allow the chelates to polymerize, or form large, [cross-linked networks](/source/Cross-link). As excess water is removed by heating, a solid polymeric resin results.<ref>{{cite journal|author=Xinyu Lu|last2=Tom S. Pine|last3=Daniel R. Mumm|last4=Jacob Brouwer |year=2007|title=Modified Pechini synthesis and characterization of Y-doped strontium titanate perovskite|journal=Solid State Ionics Forum|volume=178|issue=20|pages=1195–1199|doi=10.1016/j.ssi.2007.05.018|url=http://www.escholarship.org/uc/item/51t0g79c}}</ref> Eventually, at still higher temperatures of 500–900&nbsp;°C (930–1,650&nbsp;°F), the resin is decomposed or charred, and ultimately a [mixed oxide](/source/mixed_oxide) is obtained. Particle size is extremely small, typically 20 to 50 nanometres (although there is agglomeration of these particles into larger clusters), with intimate mixing taking place on the atomic scale.<ref>{{cite journal|author=Thomas O. Mason|year=2016|title=Encyclopedia Britannica|journal=Advanced Ceramics|url=https://www.britannica.com/technology/advanced-ceramics}}</ref>

== Uses ==
This method has been used for synthesizing over 100 mixed metal oxides including [lanthanum manganite](/source/lanthanum_manganite) for solid oxide fuel cells and [BaTiO<sub>3</sub>](/source/BaTiO3) (Lessing 1989).<ref>{{cite journal|author=Leonardo Pacheco Wendler|last2=Kethlinn Ramos|last3=Adriana Scoton Antonio Chinelatto|last4=Adilson Luiz Chinelatto|year=2014|title=Peroviskites Synthesis to SOFC Anodes|journal=Materials Science Forum|volume=805|pages=498–503|doi=10.4028/www.scientific.net/MSF.805.498}}</ref> Unlike the sol–gel process in which the metal [alkoxide](/source/alkoxide) participates in the gel-forming reactions this process is based on a [gelation reaction](/source/Gelation) between the alcohol and acid used as solvents. A polymeric resin containing a good distribution of cations is obtained which yields the oxide upon calcination. The use of [polyacrylic acid](/source/polyacrylic_acid) with higher functionality results in highly cross-linked resins containing a more uniform distribution of the reacting cations. The gel structures can be varied depending on the acid-to-alcohol ratio. A low organic content is preferred to decrease the calcination time and temperature in order to obtain fine-grained materials with low carbon contents.<ref>{{cite book|last=Kumta|first=P.N.|url=|title=Encyclopedia of Materials: Science and Technology|date=2001|publisher=|isbn=|location=|page=6588|author-link=|edition=Second}}</ref><ref>{{cite journal|author=Aluska do Nascimento Simões Braga|last2=Rosiane Maria da Costa Farias|last3=Danubia Lisbôa Costa|last4=Gelmires Araújo Neves|last5=Hélio de Lucena Lira|last6=Romualdo Rodrigues Menezes|year=2012|title=Synthesis of Mullite by the Pechini Method|journal=Materials Science Forum|volume=820|pages=107–112}}</ref>

==References==
<references />

Category:Chemical processes
Category:Thin film deposition

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Adapted from the Wikipedia article [Pechini process](https://en.wikipedia.org/wiki/Pechini_process) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Pechini_process?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.