View source for Lithium aluminate

{{Chembox
| ImageFile1=File:LiAlO2_unit_cell.png
| ImageCaption1 = <span style="color:#333333; background-color:#333333;">__</span> [[Lithium|Li]]<sup>+</sup>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#C0C0C0;background-color:#C0C0C0;">__</span> [[Aluminium|Al]]<sup>3+</sup>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#FF0000;background-color:#FF0000;">__</span> [[Oxygen|O]]<sup>2−</sup>
| Watchedfields = changed
| verifiedrevid = 415566614
| PIN = Lithium aluminate
| SystematicName = Lithium(1+) aluminate
| OtherNames = Lithium metaaluminate<br />
Lithium aluminum oxide<br />
Lithium aluminium double hydroxyde
|Section1={{Chembox Identifiers
| CASNo = 12003-67-7
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 123268
| ChemSpiderID = 109880
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 234-434-9
| MeSHName = Lithium+aluminate
| SMILES = [Li+].[O-][Al]=O
| InChI = 1/Al.Li.2O/q;+1;;-1/rAlO2.Li/c2-1-3;/q-1;+1
| InChIKey = YQNQTEBHHUSESQ-YICCBGQXAE
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Al.Li.2O/q;+1;;-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = YQNQTEBHHUSESQ-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| Li=1 | Al=1 | O=2 
| Appearance = white crystalline powder
| Density = 2.615 g/cm<sup>3</sup>, solid
| Solubility = insoluble
| MeltingPtC = 1625<ref>{{cite web |title=Lithium Aluminate |url=https://www.americanelements.com/lithium-aluminate-12003-67-7 |website=American Elements |access-date=26 July 2023}}</ref>
| BoilingPt = 
  }}
| Section4 = {{Chembox Thermochemistry
| DeltaGf = −1126.276 kJ/mol <ref name=usgs>R. Robie, B. Hemingway, and J. Fisher, “Thermodynamic Properties of Minerals and Related Substances at 298.15K and 1bar Pressure and at Higher Temperatures,” US Geol. Surv., vol. 1452, 1978.[https://pubs.usgs.gov/bul/1452/report.pdf]</ref>
| DeltaHc = 
| DeltaHf = −1188.670 kJ/mol <ref name=usgs />
| Entropy = 53.35 J/mol·K <ref name=usgs />
| HeatCapacity = 
  }}
|Section7={{Chembox Hazards
| ExternalSDS = [https://web.archive.org/web/20120318041833/http://www.espimetals.com/index.php/msds/641-Lithium%20Aluminate External MSDS]
  }}
}}

'''Lithium aluminate''' ({{chem|LiAlO|2}}), also called '''lithium aluminium oxide''', is an inorganic [[chemical compound]], an [[aluminate]] of [[lithium]].  In [[microelectronics]], lithium aluminate is considered as a [[lattice matching]] substrate for [[gallium nitride]].<ref>{{cite thesis|title=Surface Phase Transformation in Lithium Aluminate|first=Gordon|last=Mancuso|institution=[[BYU]]|date=Aug 2008|type=BS|via=CiteSeerX}}</ref><ref>{{cite tech report|publisher=Aixtron SE|title=Lithium aluminate substrate for low-cost nonpolar gallium nitride}}</ref> In [[nuclear technology]], lithium aluminate is of interest as a solid [[tritium]] breeder material, for preparing tritium fuel for [[nuclear fusion]].<ref>{{cite web |title=Lithium Aluminate Material Development |url=https://energyenvironment.pnnl.gov/projects/project_description.asp?id=383 |website=Pacific Northwest National Lab |access-date=26 July 2023}}</ref>  Lithium aluminate is a [[Layered double hydroxides|layered double hydroxide]] (LDH) with a crystal structure resembling that of [[hydrotalcite]].{{dubious|date=November 2014}}{{cln|reason=No hydroxide in the formula; does that structure refer to the hydrate (lithium aluminium hydroxide; LiAl(OH)4)?|date=January 2023}} Lithium aluminate solubility at high pH (12.5 – 13.5) is much lower than that of [[aluminium oxide]]s. In the conditioning of low- and intermediate level radioactive waste (LILW), [[lithium nitrate]] is sometimes used as additive to [[cement]] to minimise aluminium [[corrosion]] at high pH and subsequent [[hydrogen]] production.<ref>{{Cite journal
| doi = 10.1080/18811248.1995.9731793
| issn = 0022-3131
| volume = 32
| issue = 9
| pages = 912–920
| last = MATSUO
| first = Toshiaki
| author2=Takashi NISHI |author3=Masami MATSUDA |author4=Tatsuo IZUMIDA
| title = {{chem|LiNO|3}} addition to prevent hydrogen gas generation from cement-solidified aluminum wastes
| journal = Journal of Nuclear Science and Technology
| date = 1995
| doi-access = free
}}</ref> Indeed, upon addition of lithium nitrate to cement, a passive layer of {{chem|LiH(AlO|2|)|2}} · 5 {{chem|H|2|O}} is formed onto the surface of metallic aluminium waste immobilised in [[Mortar (masonry)|mortar]]. The lithium aluminate layer is insoluble in cement pore water and protects the underlying aluminium oxide covering the metallic [[aluminium]] from dissolution at high [[pH]]. It is also a pore filler.<ref>{{Cite conference
| publisher = SAE International
| last = Fujita
| first = M.
| author2=Tanaka H. |author3=Muramatsu H. |author4=Asoh H. |author5=Ono S.
| title = Corrosion resistance improvement technology of anodic oxide films on aluminum alloy that uses a lithium hydroxide solution
| location = Warrendale, PA
| accessdate = 2014-11-08
| date = 2013-10-15
| url = http://papers.sae.org/2013-32-9049/
}}</ref> This hinders the aluminium oxidation by the protons of water and reduces the hydrogen evolution rate by a factor of 10.<ref>{{Cite journal
| doi = 10.1080/18811248.1996.9732020
| issn = 0022-3131
| volume = 33
| issue = 11
| pages = 852–862
| last = MATSUO
| first = Toshiaki
| author2=Masami MATSUDA |author3=Michihiko HIRONAGA |author4=Yoshihiko HORIKAWA
| title = Effect of {{chem|LiNO|3}} on corrosion prevention of aluminum wastes after their land disposal
| journal = Journal of Nuclear Science and Technology
| date = 1996-11-01
}}</ref>

Lithium aluminate also finds its use as an inert [[electrolyte]] support material in molten [[carbonate]] [[fuel cell]]s, where the electrolyte may be a mixture of [[lithium carbonate]], [[potassium carbonate]], and [[sodium carbonate]].<ref>[http://images.freepatentsonline.com/4079171.html Molten carbonate fuel cell electrolyte] {{Webarchive|url=https://web.archive.org/web/20070929120740/http://images.freepatentsonline.com/4079171.html |date=2007-09-29 }}, United States Patent 4079171</ref>

==History==
In 1906 Weyberg described his newly synthesized compound, lithium hydrogen aluminate. This was the first known synthesis of this unique compound. He asserted that this new compound had the corresponding chemical formula:<ref>Weyberg. Chemisches Zentralblatt (1906): 645. Print.</ref>

: {{nowrap|{{chem|LiHAl|2|O|4}} + 5 {{H2O}}}}
      
In 1915 Allen and Rogers asserted that an insoluble aluminate of lithium is formed when aluminum is dissolved in a solution of lithium hydroxide. This air-dried substance had an atomic ratio of 2Li:5Al and the chemical formula:<ref name="ReferenceA">The Formation and Composition of Lithium Aluminate
Harold A. Horan and John B. Damiano
Journal of the American Chemical Society 1935 57 (12), 2434-2436</ref>

: {{nowrap|{{chem|LiH(AlO|2|)|2}} + 5 {{H2O}}}}

In 1929 Prociv recreated Allen and Rogers experiment and through a series of conductometric measurements on the saturated solution of the substance concluded that lithium and aluminum were present in the ratio of 0.8Li:2Al, which, he says, is an atomic ratio of approximately 1Li:2Al. According to him lithium aluminate may also be precipitated by the addition of a solution of lithium hydroxide to a solution of aluminum salt or by adding a solution of lithium salt to a solution of an alkali aluminate. Thus there was disagreement between Allen/Rogers and Prociv as to the composition of lithium aluminate. This may have been attributed to variations between their precipitation conditions.<ref name="ReferenceA"/>

In 1932 Dobbins and Sanders described the formation of lithium aluminate by the addition of dilute ammonia to a solution containing lithium and aluminum salt, in the presence of phelphtalein as an indicator. In their preparation of acid lithium aluminate they dissolved strips of amalgamated aluminum in normal and tenth normal solutions of lithium hydroxide. The lithium aluminate was precipitated by the addition of a solution of lithium hydroxide to a solution of aluminum salts, or by adding a solution of lithium salt to a solution of alkaline aluminate. In all cases the composition of the compound of lithium aluminate was expressed by the formula:<ref>Determination of Aluminum. Formation  Lithium Aluminate
J. T. Dobbins and J. P. Sanders
Journal of the American Chemical Society 1932 54 (1), 178-180</ref>

: {{nowrap|{{chem|Li|2|O|2|Al|2|O|2}}}}

They claimed that the formed compound contained lithium and aluminum in the atomic ratio of 2Li:5Al. Their chemical formula was simplified into the modern formulation for lithium aluminate:

: {{nowrap|{{chem|LiAlO|2}}}}

==Fields of interest==
The fundamental compound of lithium aluminate has found attention in two different fields: nuclear physics and solid-state chemistry. At least five different phases of lithium aluminate have been found.<ref name="ReferenceB">Reactivity and acidity of Li in lithium aluminum oxide (LiAlO2) phases
Richard Dronskowski
Inorganic Chemistry 1993 32 (1), 1-9</ref> The lithium aluminate crystal structure may be found in either α, β, or γ phases.<ref name="J. Jimenez-Becerril pp. 52-56">Synthesis of lithium aluminate by thermal decomposition of a lithium dawsonite-type precursor J. Jimenez-Becerril & I. Garcia-Sosa, Journal of Ceramic Processing Research. Vol. 12, No. 1, pp. 52-56 (2011)</ref>

Nuclear physicists are interested in the  {{chem|γ-LiAlO|2}} modification of lithium aluminate, because of its good performance under high neutron and electron radiation. This modification also exhibits the essential chemical, thermo physical and mechanical stability at high temperature along with the required irradiation behavior.   This phase appears to be a promising lithium ceramic, suitable as an in site tritium breeding material in future fusion reactors.<ref name="ReferenceB"/>

Solid-state chemists investigating preparational routes to lithium aluminate discovered its interesting acid-base chemistry.  The {{chem|α-LiAlO|2}} modification (but neither {{chem|β-LiAlO|2}} or {{chem|γ-LiAlO|2}}) reacts with molten benzoic acid leading to nearly total {{chem|Li|+}} proton exchange thus forming {{chem|LiHAl|2|O|4}} There is a lot of interest in the chemical reactivity among the three modifications of {{chem|LiAlO|2}}. The reasons for the {{chem|α-LiAlO|2}} modification being highly reactive and the {{chem|β-LiAlO|2}} or {{chem|γ-LiAlO|2}} modifications being totally unreactive is currently a mystery.<ref name="ReferenceB"/>

==Formation==
===Early methods===
Lithium aluminate powder preparation was based on the solid-state reactions between {{chem|Al|2|O|3}} and lithium-containing compounds like {{chem|Li|2|CO|3}}, LiOH, {{chem|Li|2|O}}, LiAc, and reactions occurred at temperatures between 400Deg C to 1000 Deg C.  Due to the evaporation of lithium at high temperatures and contamination from grinding operations, pure lithium aluminate with controlled particle size has been difficult to synthesize.<ref name="ReferenceC">Chatterjee & Naskar “Novel technique for the synthesis of lithium aluminate (LiAlO2) powders from water-based sols” Journal of Materials Science Letters, Vol 22, Issue 24, pp 1747-1749</ref>

===Current methods===
Synthesis of lithium aluminate has been essentially performed by several methods: in the solid state, by wet chemical, sol-gel, with the use of templates, various precursors, and combustion processes. The main product in a solid state reaction is the {{chem|α-LiAlO|2}} phase; in a wet chemical reaction, the main product is a solid solution of  {{chem|α-LiAlO|2}} and {{chem|γ-LiAlO|2}} phases.<ref name="J. Jimenez-Becerril pp. 52-56"/> The α-LiAlO<sub>2</sub> modification (low temperature phase), with a hexagonal structure, undergoes transformation to the γ-modification (High temperature phase), with a tetragonal structure, at about 900&nbsp;°C. The metastable β-modification, with a monoclinic structure, is assumed to transform to the γ-modification at about 900&nbsp;°C.<ref name="ReferenceC"/>

==Natural occurrence==
The compound is unknown in the natural environment. However, a related compound, LiAl<sub>5</sub>O<sub>8</sub>, is known as the very recently discovered (as of 2020) and very rare mineral chukochenite.<ref>{{Cite web|url=https://www.mindat.org/min-54350.html|title = Chukochenite}}</ref><ref>{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}}</ref>

==References==
<references/>

{{Lithium compounds}}

[[Category:Aluminates]]
[[Category:Lithium compounds]]