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{{Infobox gadolinium}} |
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'''Gadolinium''' is a [[chemical element]] with symbol '''Gd''' and [[atomic number]] 64. Gadolinium is a silvery-white, [[malleable]], and [[ductile]] [[rare earth metal]]. It is found in nature only in oxidized form, and even when separated, it usually has impurities of the other rare earths. Gadolinium was discovered in 1880 by [[Jean Charles Galissard de Marignac|Jean Charles de Marignac]], who detected its oxide by using spectroscopy. It is named after the mineral [[gadolinite]], one of the minerals in which gadolinium is found, itself named for the chemist [[Johan Gadolin]]. Pure gadolinium was first isolated by the chemist [[Paul Emile Lecoq de Boisbaudran]] around 1886. |
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Gadolinium possesses unusual [[metallurgy|metallurgical]] properties, to the extent that as little as 1% of gadolinium can significantly improve the workability and resistance to [[oxidation]] at high temperatures of [[iron]], [[chromium]], and related metals. Gadolinium as a metal or a salt absorbs [[neutron]]s and is, therefore, used sometimes for shielding in neutron [[radiography]] and in [[nuclear reactors]]. |
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Like most of the rare earths, gadolinium forms [[trivalent]] ions with fluorescent properties, and salts of gadolinium(III) are used as phosphors in various applications. |
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The kinds of gadolinium(III) ions occurring in water-soluble salts are toxic to mammals. However, [[chelate]]d gadolinium(III) compounds are far less toxic because they carry gadolinium(III) through the [[kidney]]s and out of the body before the free ion can be released into the tissues. Because of its [[paramagnetism|paramagnetic]] properties, solutions of chelated [[organic chemistry|organic]] gadolinium [[complex (chemistry)|complexes]] are used as [[intravenous]]ly administered [[gadolinium-based MRI contrast agent]]s in medical [[magnetic resonance imaging]]. |
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==Characteristics== |
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[[File:Gadolinium-2.jpg|thumb|left|15-px|A sample of gadolinium metal]] |
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===Physical properties=== |
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Gadolinium is a silvery-white [[malleable]] and [[ductile]] rare earth metal. It crystallizes in the [[hexagonal crystal system|hexagonal close-packed]] α-form at room temperature, but, when heated to temperatures above 1235 °C, it transforms into its β-form, which has a [[body-centered cubic]] structure.<ref name=Greenwood/> |
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The [[isotope]] gadolinium-157 has the highest [[thermal neutron|thermal-neutron]] [[neutron capture|capture]] cross-section among any stable nuclide: about 259,000 [[barn (unit)|barns]]. Only [[xenon-135]] has a higher capture cross-section, about 2.0 million barns, but this isotope is [[radioactive]].<ref name=barn>{{cite journal| url = http://www.ncnr.nist.gov/resources/n-lengths/elements/gd.html|publisher = NIST| title = Gadolinium| accessdate = 2009-06-06| journal = Neutron News| volume = 3| issue =3| date = 1992| page = 29}}</ref> |
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Gadolinium is believed to be [[ferromagnetism|ferromagnetic]] at temperatures below {{convert|20|C}}<ref name=CRC2/> and is strongly [[paramagnetism|paramagnetic]] above this temperature. There is evidence that gadolinium is a helical antiferromagnetic, rather than a ferromagnetic, below {{convert|20|C}}.<ref name="CoeySkumryev1999">{{cite journal|last1=Coey| first1=J. M. D.| last2=Skumryev| first2=V.|last3=Gallagher|first3=K.|journal=Nature |volume=401| issue=6748| year=1999| pages=35–36|issn=0028-0836|doi=10.1038/43363 | title = Rare-earth metals: Is gadolinium really ferromagnetic?|bibcode=1999Natur.401...35C}}</ref> Gadolinium demonstrates a [[Magnetic refrigeration#The magnetocaloric effect|magnetocaloric effect]] whereby its temperature increases when it enters a magnetic field and decreases when it leaves the magnetic field. The temperature is lowered to {{convert|5|C}} for the gadolinium [[alloy]] Gd<sub>85</sub>Er<sub>15</sub>, and this effect is considerably stronger for the alloy Gd<sub>5</sub>([[Silicon|Si]]<sub>2</sub>[[Germanium|Ge]]<sub>2</sub>), but at a much lower temperature (<{{convert|85|K}}).<ref>{{cite web|author = Gschneidner, Karl, Jr.|author2 = Gibson, Kerry|last-author-amp = yes |title = Magnetic refrigerator successfully tested| publisher = Ames Laboratory|date = 2001-12-07|url = http://www.external.ameslab.gov/news/release/01magneticrefrig.htm|accessdate = 2006-12-17|archive-url=https://web.archive.org/web/20100323011159/http://www.external.ameslab.gov/news/release/01magneticrefrig.htm|archive-date=2010-03-23}}</ref> A significant magnetocaloric effect is observed at higher temperatures, up to about 300 [[kelvin]]s, in the compounds Gd<sub>5</sub>(Si<sub>''x''</sub>Ge<sub>1−''x''</sub>)<sub>4</sub>.<ref name=r27/> |
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Individual gadolinium atoms can be isolated by encapsulating them into [[fullerene]] molecules, where they can be visualized with [[transmission electron microscope]].<ref>{{cite journal| doi = 10.1021/nl034621c| title = Evidence for the Intramolecular Motion of Gd Atoms in a Gd<sub>2</sub>@C<sub>92</sub> Nanopeapod| date = 2003| author = Suenaga, Kazu| journal = Nano Letters| volume = 3| pages = 1395| first2 = Risa| first3 = Takashi| first4 = Toshiya| first5 = Hisanori| first6 = Sumio| last2 = Taniguchi| last3 = Shimada| last4 = Okazaki| last5 = Shinohara| last6 = Iijima|bibcode = 2003NanoL...3.1395S| issue = 10 }}</ref> Individual Gd atoms and small Gd clusters can be incorporated into [[carbon nanotubes]].<ref>{{cite journal|last1=Hashimoto|first1=Ayako|last2=Yorimitsu|first2=Hideki|last3=Ajima|first3=Kumiko|last4=Suenaga|first4=Kazutomo|last5=Isobe|first5=Hiroyuki|last6=Miyawaki|first6=Jin|last7=Yudasaka|first7=Masako|last8=Iijima|first8=Sumio|last9=Nakamura|first9=Eiichi|title=Selective deposition of a gadolinium(III) cluster in a hole opening of single-wall carbon nanohorn|date=2004|journal=Proceedings of the National Academy of Sciences|volume=101|issue=23|pages=8527–8530|doi=10.1073/pnas.0400596101|bibcode=2004PNAS..101.8527H|pmid=15163794|pmc=423227|display-authors=3}}</ref> |
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===Chemical properties=== |
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{{see also|Category:Gadolinium compounds}} |
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Gadolinium combines with most elements to form Gd(III) derivatives. It also combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon, and [[arsenic]] at elevated temperatures, forming binary compounds.<ref name=Wiberg>{{Holleman&Wiberg}}</ref> |
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Unlike the other rare-earth elements, metallic gadolinium is relatively stable in dry air. However, it [[tarnish]]es quickly in moist air, forming a loosely-adhering [[gadolinium(III) oxide]] (Gd<sub>2</sub>O<sub>3</sub>): |
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:4 Gd + 3 O<sub>2</sub> → 2 Gd<sub>2</sub>O<sub>3</sub>, |
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which [[spall#Corrosion|spalls]] off, exposing more surface to oxidation. |
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Gadolinium is a strong [[reducing agent]], which reduces oxides of several metals into their elements. Gadolinium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form gadolinium hydroxide: |
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:2 Gd + 6 H<sub>2</sub>O → 2 Gd(OH)<sub>3</sub> + 3 H<sub>2</sub>. |
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Gadolinium metal is attacked readily by dilute [[sulfuric acid]] to form solutions containing the colorless Gd(III) ions, which exist as [Gd(H<sub>2</sub>O)<sub>9</sub>]<sup>3+</sup> complexes:<ref>{{cite web| url =https://www.webelements.com/gadolinium/chemistry.html| title =Chemical reactions of Gadolinium| publisher=Webelements| accessdate=2009-06-06}}</ref> |
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:2 Gd + 3 H<sub>2</sub>SO<sub>4</sub> + 18 H<sub>2</sub>O → 2 [Gd(H<sub>2</sub>O)<sub>9</sub>]<sup>3+</sup> + 3 {{chem|SO|4|2-}} + 3 H<sub>2</sub>. |
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Gadolinium metal reacts with the halogens (X<sub>2</sub>) at temperature about 200 °C: |
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:2 Gd + 3 X<sub>2</sub> → 2 GdX<sub>3</sub>. |
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====Chemical compounds==== |
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In the great majority of its compounds, gadolinium adopts the [[oxidation state]] +3. All four trihalides are known. All are white, except for the iodide, which is yellow. Most commonly encountered of the halides is [[gadolinium(III) chloride]] (GdCl<sub>3</sub>). The oxide dissolves in acids to give the salts, such as [[gadolinium(III) nitrate]]. |
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Gadolinium(III), like most lanthanide ions, forms [[coordination complex|complexes]] with high [[coordination number]]s. This tendency is illustrated by the use of the chelating agent [[DOTA (chelator)|DOTA]], an octa[[Denticity|dentate]] ligand. Salts of [Gd(DOTA)]<sup>−</sup> are useful in [[magnetic resonance imaging]]. A variety of related chelate complexes have been developed, including [[gadodiamide]]. |
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Reduced gadolinium compounds are known, especially in the solid state. Gadolinium(II) halides are obtained by heating Gd(III) halides in presence of metallic Gd in [[tantalum]] containers. Gadolinium also form sesquichloride Gd<sub>2</sub>Cl<sub>3</sub>, which can be further reduced to GdCl by annealing at 800 °C. This gadolinium(I) chloride forms platelets with layered graphite-like structure.<ref>{{cite book| page=1128| url=https://books.google.com/?id=U3MWRONWAmMC&pg=PA1128| title =Advanced inorganic chemistry| edition =6th| author= Cotton| publisher= Wiley-India| date = 2007| isbn =81-265-1338-1}}</ref> |
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===Isotopes=== |
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{{main|Isotopes of gadolinium}} |
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Naturally occurring gadolinium is composed of six stable isotopes, <sup>154</sup>Gd, <sup>155</sup>Gd, <sup>156</sup>Gd, <sup>157</sup>Gd, <sup>158</sup>Gd and <sup>160</sup>Gd, and one [[radioisotope]], <sup>152</sup>Gd, with the isotope <sup>158</sup>Gd being the most abundant (24.84% [[natural abundance]]). The predicted double beta decay of <sup>160</sup>Gd has never been observed (the only lower limit on its [[half-life]] of more than 1.3×10<sup>21</sup> years has been set experimentally<ref name="DBD">{{cite journal|author=Danevich, F. A.|display-authors=etal|title=Quest for double beta decay of <sup>160</sup>Gd and Ce isotopes|journal=Nucl. Phys. A|volume=694|date=2001|page=375|doi=10.1016/S0375-9474(01)00983-6|bibcode=2001NuPhA.694..375D|arxiv = nucl-ex/0011020 }}</ref>). |
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29 radioisotopes of gadolinium have been observed, with the most stable being <sup>152</sup>Gd (naturally occurring), with a half-life of about 1.08×10<sup>14</sup> years, and <sup>150</sup>Gd, with a half-life of 1.79×10<sup>6</sup> years. All of the remaining radioactive isotopes have half-lives of less than 75 years. The majority of these have half-lives of less than 25 seconds. Gadolinium isotopes have four metastable [[nuclear isomer|isomers]], with the most stable being <sup>143m</sup>Gd (''t''<sub>1/2</sub> = 110 seconds), <sup>145m</sup>Gd (''t''<sub>1/2</sub> = 85 seconds) and <sup>141m</sup>Gd (''t''<sub>1/2</sub> = 24.5 seconds). |
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The isotopes with [[atomic mass]]es lower than the most abundant stable isotope, <sup>158</sup>Gd, primarily decay by [[electron capture]] to isotopes of [[europium]]. At higher atomic masses, the primary [[decay mode]] is [[beta decay]], and the primary products are isotopes of [[terbium]]. |
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==History== |
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Gadolinium is named from the mineral [[gadolinite]], in turn named for [[Finland|Finnish]] chemist and [[geologist]] [[Johan Gadolin]].<ref name=Greenwood>{{Greenwood&Earnshaw2nd}}</ref> |
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In 1880, the Swiss [[chemist]] [[Jean Charles Galissard de Marignac]] observed the spectroscopic lines from gadolinium in samples of [[gadolinite]] (which actually contains relatively little gadolinium, but enough to show a spectrum) and in the separate mineral [[cerite]]. The latter mineral proved to contain far more of the element with the new spectral line. De Marignac eventually separated a mineral oxide from cerite, which he realized was the oxide of this new element. He named the oxide "[[gadolinium(III) oxide|gadolinia]]". Because he realized that "gadolinia" was the oxide of a new element, he is credited with discovery of gadolinium. The French chemist [[Paul Émile Lecoq de Boisbaudran]] carried out the separation of gadolinium metal from gadolinia in 1886. |
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==Occurrence== |
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[[File:Gadolinitas.jpg|thumb|Gadolinite]] |
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Gadolinium is a constituent in many minerals such as [[monazite]] and [[bastnäsite]], which are oxides. The metal is too reactive to exist naturally. Paradoxically, as noted above, the mineral [[gadolinite]] actually contains only traces of this element. The abundance in the Earth's crust is about 6.2 mg/kg.<ref name=Greenwood/> The main mining areas are in China, the USA, Brazil, Sri Lanka, India, and Australia with reserves expected to exceed one million tonnes. World production of pure gadolinium is about 400 tonnes per year. The only known mineral with essential gadolinium, [[lepersonnite-(Gd)]], is very rare.<ref>Deliens, M., and Piret, P., 1982. Bijvoetite et lepersonnite, carbonates hydrates d'uranyle et des terres rares de Shinkolobwe, Zaïre. Canadian Mineralogist 20, 231-238</ref><ref>{{cite web|url=http://www.mindat.org/min-2378.html |title=Lepersonnite-(Gd): Lepersonnite-(Gd) mineral information and data |website=Mindat.org |accessdate=2016-03-04}}</ref> |
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==Production== |
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Gadolinium is produced both from monazite and [[bastnäsite]]. |
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# Crushed minerals are extracted with [[hydrochloric acid]] or [[sulfuric acid]], which converts the insoluble oxides into soluble chlorides or sulfates. |
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# The acidic filtrates are partially neutralized with caustic soda to pH 3–4. [[Thorium]] precipitates as its hydroxide, and is then removed. |
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# The remaining solution is treated with [[ammonium oxalate]] to convert rare earths into their insoluble [[oxalate]]s. The oxalates are converted to oxides by heating. |
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# The oxides are dissolved in [[nitric acid]] that excludes one of the main components, [[cerium]], whose oxide is insoluble in HNO<sub>3</sub>. |
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# The solution is treated with [[magnesium nitrate]] to produce a crystallized mixture of double salts of gadolinium, [[samarium]] and [[europium]]. |
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# The salts are separated by [[ion exchange]] chromatography. |
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# The rare earth ions are then selectively washed out by a suitable complexing agent.<ref name=Greenwood/> |
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Gadolinium metal is obtained from its oxide or salts by heating it with [[calcium]] at 1450 °C in an argon atmosphere. Sponge gadolinium can be produced by reducing molten GdCl<sub>3</sub> with an appropriate metal at temperatures below 1312 °C (the melting point of Gd) at a reduced pressure.<ref name=Greenwood/> |
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==Applications==<!--few real apps described below--> |
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Gadolinium has no large-scale applications, but it has a variety of specialized uses. |
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Because <sup>157</sup>Gd has a high neutron cross-section, it is used to target tumors in neutron therapy. This element is effective for use with [[neutron radiography]] and in shielding of [[nuclear reactors]]. It is used as a secondary, emergency shut-down measure in some nuclear reactors, particularly of the [[CANDU reactor]] type.<ref name=Greenwood/> Gadolinium is also used in [[nuclear marine propulsion]] systems as a [[burnable poison#Burnable poisons|burnable poison]]. |
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Gadolinium possesses unusual [[metallurgy|metallurgic]] properties, with as little as 1% of gadolinium improving the workability and resistance of [[iron]], [[chromium]], and related [[alloy]]s to high temperatures and [[oxidation]]. |
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Gadolinium is [[paramagnetic]] at room temperature, with a [[Curie temperature|ferromagnetic Curie point]] of 20 °C.<ref name=CRC2>{{RubberBible86th|page=4.122}}</ref> Paramagnetic ions, such as gadolinium, enhance nuclear relaxation rates, making gadolinium useful for magnetic resonance imaging (MRI). Solutions of [[organic chemistry|organic]] gadolinium [[complex (chemistry)|complexes]] and gadolinium compounds are used as [[intravenous]] [[MRI contrast agent]] to enhance images in medical [[magnetic resonance imaging#Contrast agents|magnetic resonance imaging]] and [[magnetic resonance angiography]] (MRA) procedures. [[Magnevist]] is the most widespread example.<ref>{{cite book| pages=13;30|url = https://books.google.com/?id=xpCffxNrCXYC&pg=PA13| title= MRI in clinical practice| author=Liney, Gary | publisher=Springer| date = 2006| isbn = 1-84628-161-X}}</ref><ref>{{cite journal| doi = 10.1021/bc049817y| title = Next Generation, High Relaxivity Gadolinium MRI Agents| date = 2005| author = Raymond, Kenneth N.| author2 = Pierre, Valerie C.| last-author-amp = yes | journal = Bioconjugate Chemistry| volume = 16| pages = 3–8| pmid = 15656568| issue = 1}}</ref> Nanotubes packed with gadolinium, called "[[gadonanotube]]s", are 40 times more effective than the usual gadolinium contrast agent.<ref>Wendler, Ronda (December 1, 2009) [https://web.archive.org/web/20110728091851/http://www.texasmedicalcenter.org/root/en/TMCServices/News/2009/12-01/Magnets+Guide+Stem+Cells+to+Damaged+Hearts.htm Magnets Guide Stem Cells to Damaged Hearts]. Texas Medical Center.</ref> Once injected, gadolinium-based contrast agents accumulate in abnormal tissues of the brain and body, which provides a greater image contrast between normal and abnormal tissues, facilitating location of abnormal cell growths and tumors. |
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Gadolinium as a phosphor is also used in other imaging. In [[X-ray]] systems gadolinium is contained in the phosphor layer, suspended in a polymer matrix at the detector. [[Terbium]]-[[doping (semiconductors)|doped]] [[gadolinium oxysulfide]] (Gd<sub>2</sub>O<sub>2</sub>S:Tb) at the phosphor layer converts the X-rays released from the source into light. This material emits green light at 540 nm due to the presence of Tb<sup>3+</sup>, which is very useful for enhancing the imaging quality. The energy conversion of Gd is up to 20%, which means that 1/5 of the X-ray energy striking the phosphor layer can be converted into visible photons. Gadolinium oxyorthosilicate (Gd<sub>2</sub>SiO<sub>5</sub>, GSO; usually doped by 0.1–1% of [[Cerium|Ce]]) is a single crystal that is used as a [[scintillator]] in medical imaging such as [[positron emission tomography]] or for detecting neutrons.<ref>{{cite journal|doi =10.1117/1.1829713|title =Use of gadolinium oxyorthosilicate scintillators in x-ray radiometers|date =2005|author =Ryzhikov, V. D.|journal =Optical Engineering|volume =44|pages =016403|first2 = B. V.|first3 = E. N.|first4 = G. M.|first5 = A. I.|first6 = V. G.|first7 = K. A.|first8 = S. A.|last2 =Grinev|last3 =Pirogov|last4 =Onyshchenko|last5 =Ivanov|last6 =Bondar|last7 =Katrunov|last8 =Kostyukevich|bibcode = 2005OptEn..44a6403R }}</ref> |
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Gadolinium compounds are also used for making green [[phosphor]]s for color [[television|TV]] tubes. |
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Gadolinium-153 is produced in a nuclear reactor from elemental [[europium]] or enriched gadolinium targets. It has a half-life of 240 ± 10 days and emits [[gamma radiation]] with strong peaks at 41 keV and 102 keV. It is used in many quality-assurance applications, such as line sources and calibration phantoms, to ensure that nuclear-medicine imaging systems operate correctly and produce useful images of radioisotope distribution inside the patient.<ref name=gd153>{{cite web |url=http://radioisotopes.pnl.gov/gadolinium.stm |title=Gadolinium-153 |publisher=Pacific Northwest National Laboratory |accessdate=2009-06-06 |deadurl=yes |archiveurl=https://web.archive.org/web/20090527014921/http://radioisotopes.pnl.gov/gadolinium.stm |archivedate=2009-05-27 |df= }}</ref> It is also used as a gamma-ray source in X-ray absorption measurements or in [[bone density gauge]]s for [[osteoporosis]] screening, as well as in the Lixiscope portable X-ray imaging system.<ref>{{cite web| accessdate = 2009-06-06| url =http://www.ndt.net/news/lixi.htm| title =Lixi, Inc.}}</ref> |
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Gadolinium is used for making [[gadolinium yttrium garnet]] (Gd:Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>); it has [[microwave]] applications and is used in fabrication of various optical components and as substrate material for magneto-optical films. |
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[[Gadolinium gallium garnet]] (GGG, Gd<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub>) was used for imitation diamonds and for computer [[bubble memory]].<ref name=CRC>Hammond, C. R. ''The Elements'', in {{RubberBible86th}}</ref> |
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Gadolinium can also serve as an [[electrolyte]] in [[solid oxide fuel cell]]s (SOFCs). Using gadolinium as a [[dopant]] for materials like [[Cerium(IV) oxide|cerium oxide]] (in the form of [[gadolinium-doped ceria]]) creates an electrolyte with both high [[ionic conductivity]] and low operating temperatures, which are optimal for cost-effective production of fuel cells. |
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Research is being conducted on [[Refrigeration#Magnetic refrigeration|magnetic refrigeration]] near room temperature, which could provide significant efficiency and environmental advantages over conventional refrigeration methods. Gadolinium-based materials, such as Gd<sub>5</sub>(Si<sub>''x''</sub>Ge<sub>1−''x''</sub>)<sub>4</sub>, are currently the most promising materials, owing to their high Curie temperature and giant magnetocaloric effect. Pure Gd itself exhibits a large magnetocaloric effect near its [[Curie temperature]] of 20 °C, and this has sparked great interest into producing Gd alloys with a larger effect and tunable Curie temperature. In Gd<sub>5</sub>(Si<sub>''x''</sub>Ge<sub>1−''x''</sub>)<sub>4</sub>, Si and Ge compositions can be varied to adjust the Curie temperature. This technology is still very early in development, and significant material improvements still need to be made before it is commercially viable.<ref name=r27/> |
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==Biological role== |
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Gadolinium has no known native biological role, but its compounds are used as research tools in biomedicine. Gd<sup>3+</sup> compounds are components of [[MRI contrast agent]]s. It is used in various [[ion channel]] electrophysiology experiments to block sodium leak channels and stretch activated ion channels.<ref>{{cite journal| doi = 10.1111/j.1440-1681.2004.04027.x|date=August 2004| author = Yeung, Ew| author2 = Allen, Dg| title = Stretch-activated channels in stretch-induced muscle damage: role in muscular dystrophy| volume = 31| issue = 8| pages = 551–6| issn = 0305-1870| pmid = 15298550| journal = Clinical and experimental pharmacology & physiology}}</ref> |
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==Safety== |
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{{main|MRI contrast agent|Nephrogenic systemic fibrosis}} |
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As a free ion, gadolinium is reported often to be highly toxic, but MRI contrast agents are [[chelation|chelated]] compounds and are considered safe enough to be used in most persons. The toxicity of free gadolinium ions in animals is due to interference with a number of calcium-ion channel dependent processes. The [[LD50|50% lethal dose]] is about 100–200 mg/kg. Toxicities have not been reported following low dose exposure to gadolinium ions. Toxicity studies in rodents, however show that chelation of gadolinium (which also improves its solubility) decreases its toxicity with regard to the free ion by at least a factor of 100 (i.e., the lethal dose for the Gd-chelate increases by 100 times).<ref>{{cite journal|author=Penfield JG|author2=Reilly RF Jr.|last-author-amp=yes |title=What nephrologists need to know about gadolinium|journal=Nat Clin Pract Nephrol|doi=10.1038/ncpneph0660|date=2007|volume=3|issue=12|pages=654–68|pmid=18033225}}</ref> It is believed therefore that clinical toxicity of gadolinium-based contrast agents (GBCAs<ref name=GDD/>) in humans will depend on the strength of the chelating agent; however this research is still not complete.{{When|date=August 2016}} About a dozen different Gd-chelated agents have been approved as MRI contrast agents around the world.<ref>{{cite web| url = http://www.ismrm.org/special/EMEA2.pdf|title= Questions and Answers on Magnetic resonance imaging| accessdate= 2009-06-06|work=International Society for Magnetic Resonance in Medicine}}</ref><ref>{{cite web|title=Information on Gadolinium-Containing Contrast Agents |url=http://www.fda.gov/Cder/Drug/infopage/gcca/default.htm |work=US Food and Drug Administration |deadurl=yes |archiveurl=https://web.archive.org/web/20080906211904/http://www.fda.gov/Cder/Drug/infopage/gcca/default.htm |archivedate=September 6, 2008 }}</ref><ref name=Gray>Gray, Theodore (2009) ''The Elements'', Black Dog & Leventhal Publishers, {{ISBN|1-57912-814-9}}.</ref> |
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GBCAs have proved safer than the iodinated contrast agents used in X-ray radiography or [[computed tomography]]. [[Anaphylactoid reaction]]s are rare, occurring in approximately 0.03–0.1%.<ref>{{cite journal |author=Murphy KJ |author2=Brunberg JA |author3=Cohan RH |title=Adverse reactions to gadolinium contrast media: A review of 36 cases |journal=AJR Am J Roentgenol |volume=167 |issue=4 |pages=847–9 |date=1 October 1996|pmid=8819369 |doi=10.2214/ajr.167.4.8819369}}</ref> |
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Although gadolinium agents are useful for patients with renal impairment, in patients with severe renal failure requiring dialysis, there is a risk of a rare but serious illness called [[nephrogenic systemic fibrosis]] (NSF)<ref>{{cite journal|author=Thomsen, H.S.|author2=Morcos, S.K.|author3=Dawson, P.|last-author-amp=yes |title=Is there a causal relation between the administration of gadolinium-based contrast media and the development of nephrogenic systemic fibrosis (NSF)?|journal=Clinical Radiology|volume=61|issue=11|date=November 2006|pages=905–6|doi = 10.1016/j.crad.2006.09.003|pmid=17018301}}</ref> or nephrogenic fibrosing dermopathy,<ref>{{cite journal|author=Grobner T.|title=Gadolinium — a specific trigger for the development of nephrogenic fibrosing dermopathy and nephrogenic systemic fibrosis?|journal=Nephrology Dialysis Transplantation|date=April 2006|volume=21| issue=4|pages=1104–8|doi=10.1093/ndt/gfk062|pmid=16431890}}</ref> that is linked to the use of MRI contrast agents containing gadolinium. The disease resembles [[scleromyxedema]] and to some extent [[scleroderma]]. It may occur months after a contrast agent has been injected. Its association with gadolinium and not the carrier molecule is confirmed by its occurrence with various contrast materials in which gadolinium is carried by very different carrier molecules. Due to this, it is not recommended to use these agents for any individual with end-stage renal failure as they will require emergent dialysis. Similar but not identical symptoms to NSF may occur in subjects with normal or near normal renal function within hours to 2 months following the administration of GBCAs; the name "gadolinium deposition disease" (GDD) has been proposed for this condition, which occurs in the absence of pre-existent disease or subsequently developed disease of an alternate known process. The causal relationship was being investigated as of May 2016; preliminary investigation suggested a true disease process.<ref name=GDD>{{cite web| url = http://gadoliniumtoxicity.com/tag/gadolinium-deposition-disease/|title= Gadolinium Deposition Disease (GDD) in Patients with Normal Renal Function|website=Gadolinium Toxicity|date=1 November 2015|accessdate= 2016-02-03}}</ref><ref name="SemelkaRamalho2016">{{cite journal|last1=Semelka|first1=Richard C.|last2=Ramalho|first2=Miguel|last3=AlObaidy|first3=Mamdoh|last4=Ramalho|first4=Joana|title=Gadolinium in Humans: A Family of Disorders|journal=American Journal of Roentgenology|subscription=yes|volume=207|issue=2|year=2016|pages=229–233|issn=0361-803X|doi=10.2214/AJR.15.15842}}</ref> |
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Current guidelines in the United States are that dialysis patients should only receive gadolinium agents where essential and to consider performing an iodinated contrast-enhanced CT when feasible. If a contrast-enhanced MRI must be performed on a dialysis patient, it is recommended that certain high-risk contrast agents be avoided and that a lower dose be considered. The American College of Radiology recommends that contrast-enhanced MRI examinations be performed as closely before dialysis as possible as a precautionary measure, although this has not been proven to reduce the likelihood of developing NSF.<ref>{{cite book |author1=ACR Committee on Drugs |author2=Contrast Media | title = ACR Manual on Contrast Media Version 7 | date = 2010 | isbn = 978-1-55903-050-2}}</ref> |
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==References== |
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{{Reflist|30em|refs= |
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<ref name=r27>{{cite journal|author=Gschneidner, K. |author2=Pecharsky, V. |author3=Tsokol, A. |doi=10.1088/0034-4885/68/6/R04 |url=http://www.teknik.uu.se/ftf/education/magnetmatr/Projektreferenser/MCE_Reports_Progress05.pdf |title=Recent Developments in Magnetocaloric Materials |date=2005 |journal=Reports on Progress in Physics |volume=68 |issue=6 |pages=1479 |bibcode=2005RPPh...68.1479G |deadurl=yes |archiveurl=https://web.archive.org/web/20141109081936/http://www.teknik.uu.se/ftf/education/magnetmatr/Projektreferenser/MCE_Reports_Progress05.pdf |archivedate=2014-11-09 |df= }}</ref> |
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}} |
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==External links== |
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{{Commons|Gadolinium}} |
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{{wiktionary|gadolinium}} |
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* [http://rad.usuhs.edu/medpix/master.php3?mode=slide_sorter&pt_id=10978&quiz=#top Nephrogenic Systemic Fibrosis – Complication of Gadolinium MR Contrast] (series of images at MedPix website) |
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* [http://education.jlab.org/itselemental/ele064.html It's Elemental – Gadolinium] |
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* [https://web.archive.org/web/20100323011159/http://www.external.ameslab.gov/news/release/01magneticrefrig.htm Refrigerator uses gadolinium metal that heats up when exposed to magnetic field] |
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* [https://web.archive.org/web/20090309174807/http://www.fda.gov/cder/drug/infopage/gcca/qa_200705.htm FDA advisory on gadolinium-based contrast] |
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* [http://www.siaecm.org/gadolinium/index.asp Abdominal MR imaging: important considerations for evaluation of gadolinium enhancement] Rafael O.P. de Campos, Vasco Herédia, Ersan Altun, Richard C. Semelka, Department of Radiology University of North Carolina Hospitals Chapel Hill |
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{{Compact periodic table}} |
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[[Category:Gadolinium| ]] |
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[[Category:Chemical elements]] |
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[[Category:Lanthanides]] |
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[[Category:Element toxicology]] |
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[[Category:Ferromagnetic materials]] |
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[[Category:Neutron poisons]] |
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[[Category:Nuclear materials]] |
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[[Category:Reducing agents]] |
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