Gadolinium
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2008-07-14T21:33:17Z
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/* Characteristics */ section title according to wikiproject elements
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{{Elementbox_series | [[Lanthanoid|lanthanide]]s }}
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{{Elementbox_appearance_img | Gd,64| silvery white }}
{{Elementbox_atomicmass_gpm | [[1 E-25 kg|157.25]][[List of elements by atomic mass|(3)]] }}
{{Elementbox_econfig | [[[xenon|Xe]]] 4f<sup>7</sup> 5d<sup>1</sup> 6s<sup>2</sup> }}
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{{Elementbox_density_gpcm3nrt | 7.90 }}
{{Elementbox_densityliq_gpcm3mp | 7.4 }}
{{Elementbox_meltingpoint | k=1585 | c=1312 | f=2394 }}
{{Elementbox_boilingpoint | k=3546 | c=3273 | f=5923 }}
{{Elementbox_heatfusion_kjpmol | 10.05 }}
{{Elementbox_heatvaporiz_kjpmol | 301.3 }}
{{Elementbox_heatcapacity_jpmolkat25 | 37.03 }}
{{Elementbox_vaporpressure_katpa | 1836 | 2028 | 2267 | 2573 | 2976 | 3535 | comment=(calculated) }}
{{Elementbox_section_atomicprop | color1=#ffbfff | color2=black }}
{{Elementbox_crystalstruct | hexagonal }}
{{Elementbox_oxistates | 3<br />(mildly [[base (chemistry)|basic]] oxide) }}
{{Elementbox_electroneg_pauling | 1.20 }}
{{Elementbox_ionizationenergies4 | 593.4 | 1170 | 1990 }}
{{Elementbox_atomicradius_pm | [[1 E-10 m|180]] }}
{{Elementbox_atomicradiuscalc_pm | [[1 E-10 m|233]] }}
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{{Elementbox_magnetic | [[ferromagnetism|ferromagnetic]] }}
{{Elementbox_eresist_ohmm | ([[room temperature|r.t.]]) (α, poly)<br />1.310 µ}}
{{Elementbox_thermalcond_wpmkat300k | 10.6 }}
{{Elementbox_thermalexpansion_umpmk | (100 °C) (α, poly)<br />9.4 }}
{{Elementbox_speedofsound_rodmpsat20 | 2680 }}
{{Elementbox_youngsmodulus_gpa | (α form) 54.8 }}
{{Elementbox_shearmodulus_gpa | (α form) 21.8 }}
{{Elementbox_bulkmodulus_gpa | (α form) 37.9 }}
{{Elementbox_poissonratio | (α form) 0.259 }}
{{Elementbox_vickershardness_mpa | 570 }}
{{Elementbox_cas_number | 7440-54-2 }}
{{Elementbox_isotopes_begin | color1=#ffbfff | color2=black }}
{{Elementbox_isotopes_decay | mn=152 | sym=Gd
| na=0.20% | hl=1.08×10<sup>14</sup> [[year|y]]
| dm=[[alpha decay|α]] | de=2.205 | pn=148 | ps=[[samarium|Sm]] }}
{{Elementbox_isotopes_stable | mn=154 | sym=Gd | na=2.18% | n=90 }}
{{Elementbox_isotopes_stable | mn=155 | sym=Gd | na=14.80% | n=91 }}
{{Elementbox_isotopes_stable | mn=156 | sym=Gd | na=20.47% | n=92 }}
{{Elementbox_isotopes_stable | mn=157 | sym=Gd | na=15.65% | n=93 }}
{{Elementbox_isotopes_stable | mn=158 | sym=Gd | na=24.84% | n=94 }}
{{Elementbox_isotopes_decay | mn=160 | sym=Gd
| na=21.86% | hl=>1.3×10<sup>21</sup>[[year|y]]
| dm=[[Double beta minus decay|β<sup>-</sup>β<sup>-</sup>]] | de=1.7 | pn=160 | ps=[[dysprosium|Dy]] }}
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'''Gadolinium''' ({{pronEng|ˌgædəˈlɪniəm}}) is a [[chemical element]] that has the symbol '''Gd''' and [[atomic number]] 64.
__TOC__
[[Image:Gadolinium.jpg|thumb|200px|left|Gadolinium >99.9% purity]]
<br style="clear:left;" />
== Characteristics ==
Gadolinium is a silvery-white, [[malleable]] and [[ductile]] [[Rare earth element|rare-earth]] metal with a metallic lustre. It crystallizes in [[hexagon]]al, close-packed alpha form at room temperature, but, when heated to 1508 [[Kelvin|K]] or more, it transforms into its beta form, which has a [[body-centered cubic]] structure.
Unlike other rare earth elements, gadolinium is relatively stable in dry air. However, it tarnishes quickly in ''moist'' air and forms a loosely-adhering [[oxide]] that [[spall]]s off, and then exposes more surface to oxidation. Gadolinium reacts slowly with water, and it is soluble in dilute acids.
Gadolinium-157 has the highest [[thermal neutron]] [[Neutron capture|capture]] cross-section of any known nuclide with the exception of [[Xenon-135]], 49,000 [[barn (unit)|barns]], but it also has a fast burn-out rate, limiting its usefulness as a [[nuclear control rod]] material.
Gadolinium becomes [[superconductivity|superconductive]] below a critical temperature of 1.083 K. It is strongly [[paramagnetic]] at room temperature, and exhibits [[ferromagnetic]] properties below room temperature.
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 effect is considerably stronger for the gadolinium [[alloy]] [[Gadolinium|Gd]]<sub>5</sub>([[Silicon|Si]]<sub>2</sub>[[Germanium|Ge]]<sub>2</sub>)
<ref>{{cite web | author = Karl Gschneidner, Jr. and Kerry Gibson | title = MAGNETIC REFRIGERATOR SUCCESSFULLY TESTED | work = Ames Laboratory News Release | publisher = Ames Laboratory | date = 2001-12-07 | url = http://www.external.ameslab.gov/news/release/01magneticrefrig.htm | accessdate = 2006-12-17 }}</ref>.
== Applications ==
Gadolinium is used for making [[gadolinium yttrium garnet]]s, which have [[microwave]] applications, and gadolinium compounds are used for making [[phosphor]]s for colour [[television|TV]] tubes. Gadolinium is also used for manufacturing [[compact disc]]s and [[computer memory]].
Gadolinium is used in [[nuclear marine propulsion]] systems as a [[burnable poison]]. The gadolinium slows the initial reaction rate, but, as it decays, other [[neutron poison]]s accumulate, allowing for long-running cores. Gadolinium is also used as a secondary, emergency shut-down measure in some nuclear reactors, particularly of the [[CANDU reactor|CANDU]] type.
Gadolinium also 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]].
Because of their [[paramagnetism|paramagnetic]] properties, solutions of [[organic chemistry|organic]] gadolinium [[complex (chemistry)|complex]]es and gadolinium compounds are used as [[intravenous]] [[radiocontrast]] agents to enhance images in medical [[magnetic resonance imaging#Contrast agents|magnetic resonance imaging]]. [[Magnevist]] is the most widespread example.
Besides [[MRI]], gadolinium (Gd) is also used in other imaging. In [[X-ray]], gadolinium is contained in the phosphor layer, suspending 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 is to convert the X-rays releasing from the source into light. Gd can emit at 540nm (green light [[spectrum]] = 520 – 570nm), which is very useful for enhancing the imaging quality of the [[X-ray]] that is exposed to the photographic film. Beside Gd's spectrum range, the compound also has a K-edge at 50 kiloelectron volt (keV), which means its absorption of [[X-ray]] through [[photoelectric]] interactions is great. The energy conversion of Gd is up to 20%, which means, one-fifth of the X-ray striking on the phosphor layer can be converted into light 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]] (PET) or for detecting neutrons.
[[Gadolinium gallium garnet]] (Gd<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub>) is a material with good optical properties, and is used in fabrication of various optical components and as substrate material for magneto–optical films.
In the future, [[gadolinium ethyl sulfate]], which has extremely low noise characteristics, may be used in [[maser]]s. Furthermore, gadolinium's high magnetic moment and low [[Curie temperature]] (which lies just at room temperature) suggest applications as a magnetic component for sensing hot and cold.
Due to extremely high neutron cross-section of gadolinium, this element is very effective for use with [[neutron radiography]].
== History ==
In [[1880]], [[Switzerland|Swiss]] [[chemist]] [[Jean Charles Galissard de Marignac]] observed spectroscopic lines due to gadolinium in samples of [[didymium]] and [[gadolinite]]; [[France|French]] chemist [[Paul Émile Lecoq de Boisbaudran]] separated [[gadolinium(III) oxide|gadolinia]], the [[oxide]] of Gadolinium, from Mosander's [[yttria]] in [[1886]]. The element itself was isolated only recently.
Gadolinium, like the mineral [[gadolinite]], is named after [[Finland|Finnish]] chemist and [[geologist]] [[Johan Gadolin]].
In older literature, the natural form of the element is often called an ''earth'', meaning that the element came from Earth. In fact, gadolinium is the element that comes from the earth, gadolinia. Earths are compounds of the element and one or more other elements. The two most common combining-elements are oxygen and sulfur. For example, gadolinia contains gadolinium oxide (Gd<sub>2</sub>O<sub>3</sub>).
== Biological role ==
Gadolinium has no known native biological role, but in research on biological systems it has a few roles. It is used as a component of [[MRI contrast agent]]s, as, in the 3+ oxidation state, the metal has 7 unpaired f electrons. This causes water around the contrast agent to [[Relaxation (NMR)|relax]] quickly, enhancing the quality of the MRI scan. Second, as a member of the [[Lanthanoid|lanthanides]], it is used in various [[ion channel]] electrophysiology experiments, where it is used to block sodium leak channels, as well as to stretch activated ion channels.
Gadolinium-based contrast agents are dangerous in patients with kidney disease. The contrast agent is normally chelated as it is expected to pass through the body quickly. In patients with kidney disease, the excretion is slower and the gadolinium becomes unbound, causing serious health issues.
== Occurrence ==
Gadolinium is never found in nature as the free element, but is contained in many rare minerals such as [[monazite]] and [[bastnäsite]]. It occurs only in trace amounts in the mineral [[gadolinite]], which was also named after [[Johan Gadolin]]. Today, it is prepared by [[ion exchange]] and [[solvent extraction]] techniques, or by the reduction of its anhydrous fluoride with metallic [[calcium]].
== Value ==
In [[1994]], the cost of gadolinium was about [[United States dollar|US$]] 0.12 per [[gram]], and it has only increased in value by about US$ 0.01 per gram since then.<ref>{{cite journal
| author = James B. Hedrick
| year = 1994
| month =
| title = Rare Earths
| journal = USGS Commodity Statistics and Information
| volume =
| issue =
| pages = 72
| id =[http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/740494.pdf]}}</ref>:
::1994.....$55 per [[pound (mass)|pound]] (or $0.121 per gram)
::1995.....$55 per pound (or $0.121 per gram)
::1996.....$115 per [[kilogram]] (or $0.115 per gram)
::1997.....$115 per kilogram (or $0.115 per gram)
::1998.....$115 per kilogram (or $0.115 per gram)
::1999.....$115 per kilogram (or $0.115 per gram)
::2000.....$130 per kilogram (or $0.13 per gram)
::2001.....$130 per kilogram (or $0.13 per gram)
::2002.....$130 per kilogram (or $0.13 per gram)
::2003.....$130 per kilogram (or $0.13 per gram)
::2004.....$130 per kilogram (or $0.13 per gram)
::2005.....$130 per kilogram (or $0.13 per gram)
== Compounds ==
Compounds of gadolinium include:
* [[Fluoride]]s: [[gadolinium(III) fluoride|GdF<sub>3</sub>]]
* [[Chloride]]s: [[gadolinium(III) chloride|GdCl<sub>3</sub>]]
* [[Bromide]]s: [[gadolinium(III) bromide|GdBr<sub>3</sub>]]
* [[Nitrate]]s: [[gadolinium nitrate|Gd(NO<sub>3</sub>)<sub>3</sub>]]
* [[Iodide]]s: [[gadolinium(III) iodide|GdI<sub>3</sub>]]
* [[Oxide]]s: [[gadolinium(III) oxide|Gd<sub>2</sub>O<sub>3</sub>]]
* [[Sulfide]]s: [[gadolinium(III) sulfide|Gd<sub>2</sub>S<sub>3</sub>]]
* [[Nitride]]s: [[gadolinium(III) nitride|GdN]]
* [[Organic compound|Organics]]: [[gadodiamide]]
''See also [[:Category:Gadolinium compounds|gadolinium compounds]].''
== Isotopes ==
{{main|Isotopes of gadolinium}}
Naturally-occurring gadolinium is composed of 5 stable [[isotope]]s, <sup>154</sup>Gd, <sup>155</sup>Gd, <sup>156</sup>Gd, <sup>157</sup>Gd and <sup>158</sup>Gd, and 2 [[radioisotope]]s, <sup>152</sup>Gd and <sup>160</sup>Gd, with <sup>158</sup>Gd being the most abundant (24.84% [[natural abundance]]).
Thirty radioisotopes have been characterized, with the most stable being <sup>160</sup>Gd with a [[half-life]] of more than 1.3×10<sup>21</sup> years (the decay has not been observed - only the lower limit on the half-life is known), alpha-decaying <sup>152</sup>Gd with a half-life of 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 isotopes are radioactive, having half-lives less than 74.7 years. The majority of these have half-lives less than 24.6 seconds. Gadolinium isotopes have 4 metastable [[nuclear isomer|isomer]]s, with the most stable being <sup>143m</sup>Gd (t<sub>½</sub> 110 seconds), <sup>145m</sup>Gd (t<sub>½</sub> 85 seconds) and <sup>141m</sup>Gd (t<sub>½</sub> 24.5 seconds).
The primary [[decay mode]] at atomic weights lower than the most abundant stable isotope, <sup>158</sup>Gd, is [[electron capture]], and the primary mode at higher atomic weights is [[beta decay]]. The primary [[decay product]]s for isotopes of weights lower than <sup>158</sup>Gd are the element Eu ([[europium]]) isotopes and the primary products at higher weights are the element Tb ([[terbium]]) isotopes.
Gadolinium-153 has a half-life of 240.4 ±10 days and emits gamma radiation with strong peaks at 41keV and 102keV. It is used as a gamma ray source in x-ray absorptiometry or bone density gauges for [[osteoporosis]] screening, and in the Lixiscope portable x-ray imaging system.
== Precautions ==
As with the other lanthanides, gadolinium compounds are of low to moderate [[toxicity]], although their toxicity has not been investigated in detail. Also, in patients on dialysis, there is data suggesting that it may cause [[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 | year=2006 | month=Apr | volume=21| issue=4 | pages=1104–8 | date=[[2006-01-23]] | doi=10.1093/ndt/gfk062 | pmid=16431890}}</ref> as a side effect of [[MRI]] investigations that require the use of a gadolinium based contrast agent.
== References ==
<references/>
== General references ==
*[http://periodic.lanl.gov/elements/64.html Los Alamos National Laboratory – Gadolinium]
== External links ==
{{Commons|Gadolinium}}
{{wiktionary|gadolinium}}
* [http://www.webelements.com/webelements/elements/text/Gd/index.html WebElements.com – Gadolinium]
* [http://rad.usuhs.edu/medpix/master.php3?mode=slide_sorter&pt_id=10978&quiz=#top Nephrogenic Systemic Fibrosis – Complication of Gadolinium MR Contrast]
* [http://education.jlab.org/itselemental/ele064.html It's Elemental – Gadolinium]
* [http://www.external.ameslab.gov/news/release/01magneticrefrig.htm refrigerator uses gadolinium metal that heats up when exposed to magnetic field]
* [http://www.fda.gov/cder/drug/infopage/gcca/qa_200705.htm FDA Advisory on Gadolinium-Based Contrast]
{{clear}}
{{Compact periodic table}}
[[Category:Chemical elements]]
[[Category:Lanthanides]]
[[Category:Ferromagnetic materials]]
[[Category:Element toxicology]]
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