Editing Magnesium oxide (section)

===Niche uses===
[[Image:MgOcrystal.JPG|thumb|left|140px|Unpolished MgO crystal]]
* As a food additive, it is used as an [[anticaking agent]]. It is known to the US [[Food and Drug Administration]] for cacao products; canned peas; and frozen dessert.<ref>{{cite web |title=Compound Summary for CID 14792 – Magnesium Oxide |url=https://pubchem.ncbi.nlm.nih.gov/compound/magnesium_oxide |publisher=PubChem}}</ref> It has an [[E number]] of E530.
* As a reagent in the installation of the carboxybenzyl (Cbz) group using [[benzyl chloroformate]] in [[ethyl acetate|EtOAc]] for the [[protecting group|N-protection]] of [[amine]]s and [[amide]]s.<ref>{{Cite journal|last=Dymicky|first=M.|date=1989-02-01|title=Preparation of Carbobenzoxy-<small>L</small>-Tyrosine Methyl and Ethyl Esters and of the Corresponding Carbobenzoxy Hydrazides|journal=Organic Preparations and Procedures International|volume=21|issue=1|pages=83–90|doi=10.1080/00304948909356350|issn=0030-4948}}</ref>
* [[Doping (semiconductor)|Doping]] MgO (about 1–5% by weight) into [[hydroxyapatite]], a [[bioceramic]] mineral, increases the [[fracture toughness]] by migrating to grain boundaries, where it reduces grain size and changes the fracture mode from [[intergranular fracture|intergranular]] to [[transgranular fracture|transgranular]].<ref>{{cite journal |doi=10.1016/j.ceramint.2013.04.098 |last1=Tan |first1=C.Y. |last2=Yaghoubi |first2=A. |last3=Ramesh |first3=S. |last4=Adzila |first4=S. |last5=Purbolaksono |first5=J. |last6=Hassan |first6=M.A. |last7=Kutty |first7=M.G. |date=December 2013 |title=Sintering and mechanical properties of MgO-doped nanocrystalline hydroxyapatite |url=http://www.aun.edu.eg/reserches_files/13211.pdf |journal=Ceramics International |volume=39 |issue=8 |pages=8979–8983 |access-date=2015-08-08 |archive-date=2017-03-12 |archive-url=https://web.archive.org/web/20170312033742/http://www.aun.edu.eg/reserches_files/13211.pdf |url-status=dead }}</ref><ref >{{cite journal | last1=Tan | first1=Chou Yong | last2=Singh | first2=Ramesh | last3=Tolouei | first3=R. | last4=Sopyan | first4=Iis | last5=Teng | first5=Wan Dung | title=Synthesis of High Fracture Toughness of Hydroxyapatite Bioceramics | journal=Advanced Materials Research | volume=264-265 | year=2011 | issn=1662-8985 | doi=10.4028/www.scientific.net/amr.264-265.1849 | pages=1849–1855| s2cid=137578750 }}</ref> 
* Pressed MgO is used as an optical material. It is transparent from 0.3 to 7&nbsp;μm. The [[refractive index]] is 1.72 at 1&nbsp;μm and the [[Abbe number]] is 53.58. It is sometimes known by the [[Eastman Kodak]] trademarked name Irtran-5, although this designation is obsolete. Crystalline pure MgO is available commercially and has a small use in infrared optics.<ref>{{cite journal|title=Index of Refraction of Magnesium Oxide|author1=Stephens, Robert E.|author2=Malitson, Irving H.|name-list-style=amp|journal=Journal of Research of the National Bureau of Standards|volume=49|issue=4|year=1952|pages=249–252|doi=10.6028/jres.049.025|doi-access=free}}</ref>
* An aerosolized solution of MgO is used in library science and collections management for the [[deacidification]] of at-risk paper items. In this process, the alkalinity of MgO (and similar compounds) neutralizes the relatively high acidity characteristic of low-quality paper, thus slowing the rate of deterioration.<ref name="LibraryofCongress">{{cite web|title=Mass Deacidification: Saving the Written Word|url=https://www.loc.gov/preservation/scientists/projects/mass_deacid.html|work=Library of Congress|access-date=26 September 2011}}</ref>
* Magnesium oxide is used as an oxide barrier in [[Spintronics|spin-tunneling devices]]. Owing to the crystalline structure of its thin films, which can be deposited by [[magnetron sputtering]], for example, it shows characteristics superior to those of the commonly used amorphous Al<sub>2</sub>O<sub>3</sub>. In particular, [[spin polarization]] of about 85% has been achieved with MgO<ref>{{Cite journal 
| last1 = Parkin | first1 = S. S. P. 
| last2 = Kaiser | first2 = C. 
| last3 = Panchula | first3 = A. 
| last4 = Rice | first4 = P. M. 
| last5 = Hughes | first5 = B. 
| last6 = Samant | first6 = M. 
| last7 = Yang | first7 = S. H. 
| doi = 10.1038/nmat1256 
| title = Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers 
| journal = Nature Materials 
| volume = 3 
| issue = 12 
| pages = 862–867 
| year = 2004 
| pmid = 15516928 
| bibcode = 2004NatMa...3..862P | s2cid = 33709206 
}}</ref> versus 40–60&nbsp;% with aluminium oxide.<ref>{{Cite journal | last1 = Monsma | first1 = D. J. | last2 = Parkin | first2 = S. S. P. | doi = 10.1063/1.127097 | title = Spin polarization of tunneling current from ferromagnet/Al<sub>2</sub>O<sub>3</sub> interfaces using copper-doped aluminum superconducting films | journal = Applied Physics Letters | volume = 77 | issue = 5 | page = 720 | year = 2000 |bibcode = 2000ApPhL..77..720M }}</ref> The value of [[tunnel magnetoresistance]] is also significantly higher for MgO (600% at room temperature and 1,100&nbsp;% at 4.2 K<ref>{{Cite journal | last1 = Ikeda | first1 = S. | last2 = Hayakawa | first2 = J. | last3 = Ashizawa | first3 = Y. | last4 = Lee | first4 = Y. M. | last5 = Miura | first5 = K. | last6 = Hasegawa | first6 = H. | last7 = Tsunoda | first7 = M. | last8 = Matsukura | first8 = F. | last9 = Ohno | first9 = H. | doi = 10.1063/1.2976435 | title = Tunnel magnetoresistance of 604% at 300 K by suppression of Ta diffusion in CoFeB/MgO/CoFeB pseudo-spin-valves annealed at high temperature | journal = Applied Physics Letters | volume = 93 | issue = 8 | page = 082508 | year = 2008 |bibcode = 2008ApPhL..93h2508I | s2cid = 122271110 }}</ref>) than Al<sub>2</sub>O<sub>3</sub> (ca. 70% at room temperature<ref>{{Cite journal | last1 = Wang | first1 = D. | last2 = Nordman | first2 = C. | last3 = Daughton | first3 = J. M. | last4 = Qian | first4 = Z. | last5 = Fink | first5 = J. | doi = 10.1109/TMAG.2004.830219 | title = 70% TMR at Room Temperature for SDT Sandwich Junctions with CoFeB as Free and Reference Layers | journal = IEEE Transactions on Magnetics | volume = 40 | issue = 4 | page = 2269 | year = 2004 | citeseerx = 10.1.1.476.8544 | bibcode = 2004ITM....40.2269W | s2cid = 20439632 }}</ref>).
* MgO is a common pressure transmitting medium used in high pressure apparatuses like the [[multi-anvil press]].<ref>{{Cite journal |last1=Wang |first1=Haikuo |last2=He |first2=Duanwei |last3=Yan |first3=Xiaozhi |last4=Xu |first4=Chao |last5=Guan |first5=Junwei |last6=Tan |first6=Ning |last7=Wang |first7=Wendan |date=December 2011 |title=Quantitative measurements of pressure gradients for the pyrophyllite and magnesium oxide pressure-transmitting mediums to 8 GPa in a large-volume cubic cell |url=http://www.tandfonline.com/doi/abs/10.1080/08957959.2011.614238 |journal=High Pressure Research |language=en |volume=31 |issue=4 |pages=581–591 |doi=10.1080/08957959.2011.614238 |bibcode=2011HPR....31..581W |issn=0895-7959}}</ref>