Magnesium oxide was historically known asmagnesia alba (literally, the white mineral fromMagnesia), to differentiate it frommagnesia nigra, a black mineral containing what is now known asmanganese.
While "magnesium oxide" normally refers to MgO, the compoundmagnesium peroxide MgO2 is also known. According to evolutionary crystal structure prediction,[11] MgO2 is thermodynamically stable at pressures above 116 GPa (gigapascals), and a semiconductingsuboxide Mg3O2 is thermodynamically stable above 500 GPa. Because of its stability, MgO is used as a model system for investigating vibrational properties of crystals.[12]
Calcining at different temperatures produces magnesium oxide of different reactivity. High temperatures 1500 – 2000 °C diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as arefractory. Calcining temperatures 1000 – 1500 °C produce hard-burned magnesia, which has limited reactivity and calcining at lower temperature, (700–1000 °C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia. Although some decomposition of the carbonate to oxide occurs at temperatures below 700 °C, the resulting materials appear to reabsorb carbon dioxide from the air.[citation needed]
MgO is prized as arefractory material, i.e. a solid that is physically and chemically stable at high temperatures. It has the useful attributes of high thermal conductivity and low electrical conductivity. According to a 2006 reference book:[14]
By far the largest consumer of magnesia worldwide is the refractory industry, which consumed about 56% of the magnesia in the United States in 2004, the remaining 44% being used in agricultural, chemical, construction, environmental, and other industrial applications.
Among metal oxide nanoparticles, magnesium oxide nanoparticles (MgO NPs) have distinct physicochemical and biological properties, including biocompatibility, biodegradability, high bioactivity, significant antibacterial properties, and good mechanical properties, which make it a good choice as a reinforcement in composites.[15]
It is used extensively as an electrical insulator in tubular constructionheating elements as in electricstove andcooktop heating elements. There are severalmesh sizes available and most commonly used ones are 40 and 80 mesh per theAmerican Foundry Society. The extensive use is due to its high dielectric strength and average thermal conductivity. MgO is usually crushed and compacted with minimal airgaps or voids.
It is a principal fireproofing ingredient in construction materials. As a construction material,magnesium oxide wallboards have several attractive characteristics: fire resistance, termite resistance, moisture resistance, mold and mildew resistance, and strength, but also a severe downside as it attracts moisture and can cause moisture damage to surrounding materials.[18][14][1]
Magnesium oxide is used for relief of heartburn and indigestion, as anantacid, magnesium supplement, and as a short-termlaxative. It is also used to improve symptoms ofindigestion. Side effects of magnesium oxide may include nausea and cramping.[19] In quantities sufficient to obtain a laxative effect, side effects of long-term use may rarely causeenteroliths to form, resulting inbowel obstruction.[20]
Magnesium oxide is used extensively in the soil andgroundwater remediation, wastewater treatment, drinking water treatment, air emissions treatment, and waste treatment industries for its acid buffering capacity and related effectiveness in stabilizing dissolved heavy metal species.[according to whom?]
Many heavy metals species, such aslead andcadmium, are least soluble in water at mildly basic conditions (pH in the range 8–11). Solubility of metals increases their undesired bioavailability and mobility in soil and groundwater. Granular MgO is often blended into metals-contaminating soil or waste material, which is also commonly of a low pH (acidic), in order to drive thepH into the 8–10 range. Metal-hydroxide complexes tend toprecipitate out of aqueous solution in the pH range of 8–10.
MgO is packed in bags aroundtransuranic waste in the disposal cells (panels) at theWaste Isolation Pilot Plant, as a CO2 getter to minimize the complexation ofuranium and otheractinides bycarbonate ions and so to limit thesolubility ofradionuclides. The use of MgO is preferred overCaO since the resultinghydration product (Mg(OH) 2) is less soluble and releases lesshydration heat. Another advantage is to impose a lowerpH value (about 10.5) in case of accidental water ingress into the dry salt layers, in contast to the more solubleCa(OH) 2 which would create a higher pH of 12.5 (stronglyalkaline conditions). TheMg2+ cation being the second most abundant cation inseawater and inrocksalt, the potential release of magnesium ions dissolving inbrines intruding thedeep geological repository is also expected to minimize thegeochemical disruption.[21]
Pressed MgO is used as an optical material. It is transparent from 0.3 to 7 μm. Therefractive index is 1.72 at 1 μm and theAbbe number is 53.58. It is sometimes known by theEastman Kodak trademarked name Irtran-5, although this designation is obsolete. Crystalline pure MgO is available commercially and has a small use in infrared optics.[26]
An aerosolized solution of MgO is used in library science and collections management for thedeacidification 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.[27]
Magnesium oxide is used as an oxide barrier inspin-tunneling devices. Owing to the crystalline structure of its thin films, which can be deposited bymagnetron sputtering, for example, it shows characteristics superior to those of the commonly used amorphous Al2O3. In particular,spin polarization of about 85% has been achieved with MgO[28] versus 40–60 % with aluminium oxide.[29] The value oftunnel magnetoresistance is also significantly higher for MgO (600% at room temperature and 1,100 % at 4.2 K[30]) than Al2O3 (ca. 70% at room temperature[31]).
MgO is a common pressure transmitting medium used in high pressure apparatuses like themulti-anvil press.[32]
Magnesia is used inbrake linings for its heat conductivity and intermediate hardness.[33] It helps dissipate heat from friction surfaces, preventing overheating, while minimizing wear on metal components.[34] Its stability under high temperatures ensures reliable and durable braking performance inautomotive and industrial applications.[35]
Inthin film transistors(TFTs), MgO is often used as a dielectric material or an insulator due to its high thermal stability, excellent insulating properties, and widebandgap.[36] Optimized IGZO/MgO TFTs demonstrated anelectron mobility of 1.63 cm²/Vs, an on/off current ratio of 10⁶, and a subthreshold swing of 0.50 V/decade at −0.11 V.[37] These TFTs are integral to low-power applications, wearable devices, and radiation-hardened electronics, contributing to enhanced efficiency and durability across diverse domains.[38][39]
^Mármol, Gonzalo; Savastano, Holmer (July 2017). "Study of the degradation of non-conventional MgO-SiO 2 cement reinforced with lignocellulosic fibers".Cement and Concrete Composites.80:258–267.doi:10.1016/j.cemconcomp.2017.03.015.
^Tatekawa Y, Nakatani K, Ishii H, et al. (1996). "Small bowel obstruction caused by a medication bezoar: report of a case".Surgery Today.26 (1):68–70.doi:10.1007/BF00311997.PMID8680127.S2CID24976010.
^Dymicky, M. (1989-02-01). "Preparation of Carbobenzoxy-L-Tyrosine Methyl and Ethyl Esters and of the Corresponding Carbobenzoxy Hydrazides".Organic Preparations and Procedures International.21 (1):83–90.doi:10.1080/00304948909356350.ISSN0030-4948.
^Parkin, S. S. P.; Kaiser, C.; Panchula, A.; Rice, P. M.; Hughes, B.; Samant, M.; Yang, S. H. (2004). "Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers".Nature Materials.3 (12):862–867.Bibcode:2004NatMa...3..862P.doi:10.1038/nmat1256.PMID15516928.S2CID33709206.
^Monsma, D. J.; Parkin, S. S. P. (2000). "Spin polarization of tunneling current from ferromagnet/Al2O3 interfaces using copper-doped aluminum superconducting films".Applied Physics Letters.77 (5): 720.Bibcode:2000ApPhL..77..720M.doi:10.1063/1.127097.
^Ikeda, S.; Hayakawa, J.; Ashizawa, Y.; Lee, Y. M.; Miura, K.; Hasegawa, H.; Tsunoda, M.; Matsukura, F.; Ohno, H. (2008). "Tunnel magnetoresistance of 604% at 300 K by suppression of Ta diffusion in CoFeB/MgO/CoFeB pseudo-spin-valves annealed at high temperature".Applied Physics Letters.93 (8): 082508.Bibcode:2008ApPhL..93h2508I.doi:10.1063/1.2976435.S2CID122271110.
^Su, Zhan; Zhang, Xiao (2024). "Effect of substrate temperature on growth mechanism and properties of PEALD-MgO dielectric films for amorphous-IGZO TFTs".Surface and Coatings Technology.483: 130819.doi:10.1016/j.surfcoat.2024.130819.
^Zhao, Cheng; Li, Jun (2017). "Mg Doping to Simultaneously Improve the Electrical Performance and Stability of MgInO Thin-Film Transistors".IEEE Transactions on Electron Devices.64 (5):2216–2220.Bibcode:2017ITED...64.2216Z.doi:10.1109/TED.2017.2678544.
