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Gadolinium - Wikipedia, the free encyclopedia /**/ /**/ if (wgNotice != '') document.writeln(wgNotice); Gadolinium From Wikipedia, the free encyclopedia Jump to: navigation, search 64europium ← gadolinium → terbium-↑Gd↓Cm Periodic Table - Extended Periodic TableGeneralName, Symbol, Numbergadolinium, Gd, 64Element categorylanthanidesGroup, Period, Blockn/a, 6, fAppearancesilvery white Standard atomic weight157.25(3) g·mol−1Electron configuration[Xe] 4f7 5d1 6s2Electrons per shell2, 8, 18, 25, 9, 2Physical propertiesPhasesolidDensity (near r.t.)7.90 g·cm−3Liquid density at m.p.7.4 g·cm−3Melting point1585 K(1312 °C, 2394 °F)Boiling point3546 K(3273 °C, 5923 °F)Heat of fusion10.05 kJ·mol−1Heat of vaporization301.3 kJ·mol−1Specific heat capacity(25 °C) 37.03 J·mol−1·K−1Vapor pressure (calculated)P(Pa)1101001 k10 k100 kat T(K)183620282267257329763535Atomic propertiesCrystal structurehexagonalOxidation states3(mildly basic oxide)Electronegativity1.20 (Pauling scale)Ionization energies(more)1st: 593.4 kJ·mol−12nd: 1170 kJ·mol−13rd: 1990 kJ·mol−1Atomic radius180 pmAtomic radius (calc.)233 pmMiscellaneousMagnetic orderingferromagneticElectrical resistivity(r.t.) (α, poly)1.310 µΩ·mThermal conductivity(300 K) 10.6 W·m−1·K−1Thermal expansion(100 °C) (α, poly)9.4 µm/(m·K)Speed of sound (thin rod)(20 °C) 2680 m/sYoung's modulus(α form) 54.8 GPaShear modulus(α form) 21.8 GPaBulk modulus(α form) 37.9 GPaPoisson ratio(α form) 0.259Vickers hardness570 MPaCAS registry number7440-54-2Most-stable isotopesMain article: Isotopes of gadoliniumisoNAhalf-lifeDMDE (MeV)DP152Gd0.20%1.08×1014 yα2.205148Sm154Gd2.18%154Gd is stable with 90 neutrons155Gd14.80%155Gd is stable with 91 neutrons156Gd20.47%156Gd is stable with 92 neutrons157Gd15.65%157Gd is stable with 93 neutrons158Gd24.84%158Gd is stable with 94 neutrons160Gd21.86%>1.3×1021yβ-β-1.7160DyReferencesGadolinium (pronounced /ˌgædəˈlɪniəm/) is a chemical element that has the symbol Gd and atomic number 64.Contents1 Characteristics2 Applications3 History4 Biological role5 Occurrence6 Value7 Compounds8 Isotopes9 Precautions10 References11 General references12 External links//  Gadolinium >99.9% purity[edit] CharacteristicsGadolinium is a silvery-white, malleable and ductile rare-earth metal with a metallic lustre. It crystallizes in hexagonal, close-packed alpha form at room temperature, but, when heated to 1508 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, forming a loosely-adhering oxide which spalls off, exposing more surface to oxidation. Gadolinium reacts slowly with water, and is soluble in dilute acids.Gadolinium-157 has the highest thermal neutron capture cross-section of any known nuclide with the exception of xenon-135, 49,000 barns, but it also has a fast burn-out rate, limiting its usefulness as a nuclear control rod material. Gadolinium compounds (oxide) would make a fine control blade absorber, it is just much more expensive than boron carbide, which is the primary absorber in control blades. Also, the "burn-out rate" mentioned above is the flux (n/cm2*s) multiplied by cross-section (cm2). They are not separate quantities; big cross-section gives big "burn-out rate". Also, gadolinia does not burn-out with neutron absorption, it tranes-up in atomic number but remains Gd. The number of Gd atoms remains constant; negative reactivity goes away because Gd atoms have been traned to isotopes that have lower absorption cross-sections. 160Gd has less than one barn thermal neutron absorption cross section and is no longer an effective poison (http://www.ncnr.nist.gov/resources/n-lengths/elements/gd.html).Gadolinium is strongly paramagnetic at room temperature, and exhibits ferromagnetic properties below room temperature.Gadolinium demonstrates a 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 Gd5(Si2Ge2) [1].[edit] ApplicationsGadolinium is used for making gadolinium yttrium garnets, which have microwave applications, and gadolinium compounds are used for making phosphors for colour TV tubes. Gadolinium is also used for manufacturing compact discs and computer memory.Gadolinium is used in nuclear marine propulsion systems as a burnable poison. Gadolinium is also used as a secondary, emergency shut-down measure in some nuclear reactors, particularly of the CANDU type.Gadolinium also possesses unusual metallurgic properties, with as little as 1% of gadolinium improving the workability and resistance of iron, chromium, and related alloys to high temperatures and oxidation.Because of their paramagnetic properties, solutions of organic gadolinium complexes and gadolinium compounds are used as intravenous radiocontrast agents to enhance images in medical 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-doped gadolinium oxysulfide (Gd2O2S: 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 (Gd2SiO5, GSO; usually doped by 0.1-1% of 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 (Gd3Ga5O12) 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 masers. 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.[edit] HistoryIn 1880, Swiss chemist Jean Charles Galissard de Marignac observed spectroscopic lines due to gadolinium in samples of didymium and gadolinite; French chemist Paul Émile Lecoq de Boisbaudran separated 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 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 (Gd2O3).[edit] Biological roleGadolinium 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 agents, as, in the 3+ oxidation state, the metal has 7 unpaired f electrons. This causes water around the contrast agent to relax quickly, enhancing the quality of the MRI scan. Second, as a member of the 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.[edit] OccurrenceGadolinium 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.[edit] ValueIn 1994, the cost of gadolinium was about US$ 0.12 per gram, and it has only increased in value by about US$ 0.01 per gram since then.[2]:1994.....$55 per 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)[edit] CompoundsCompounds of gadolinium include:Fluorides: GdF3Chlorides: GdCl3Bromides: GdBr3Nitrates: Gd(NO3)3Iodides: GdI3Oxides: Gd2O3Sulfides: Gd2S3Nitrides: GdNOrganics: gadodiamideSee also gadolinium compounds.[edit] IsotopesMain article: Isotopes of gadoliniumNaturally-occurring gadolinium is composed of 5 stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd and 158Gd, and 2 radioisotopes, 152Gd and 160Gd, with 158Gd being the most abundant (24.84% natural abundance).Thirty radioisotopes have been characterized, with the most stable being 160Gd with a half-life of more than 1.3×1021 years (the decay has not been observed - only the lower limit on the half-life is known), alpha-decaying 152Gd with a half-life of 1.08×1014 years, and 150Gd with a half-life of 1.79×106 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 isomers, with the most stable being 143mGd (t½ 110 seconds), 145mGd (t½ 85 seconds) and 141mGd (t½ 24.5 seconds).The primary decay mode at atomic weights lower than the most abundant stable isotope, 158Gd, is electron capture, and the primary mode at higher atomic weights is beta decay. The primary decay products for isotopes of weights lower than 158Gd 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.[edit] PrecautionsAs with the other lanthanides, gadolinium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Also, in patients with renal failure or other pro-inflammatory conditions, there is data associating its use with development of nephrogenic fibrosing dermopathy[3] as a side effect of gadolinium chelates used as a contrast agent for MRI examinations.[edit] References^ Karl Gschneidner, Jr. and Kerry Gibson (2001-12-07). "MAGNETIC REFRIGERATOR SUCCESSFULLY TESTED". Ames Laboratory News Release. Ames Laboratory. Retrieved on 2006-12-17.^ James B. Hedrick (1994). "Rare Earths". USGS Commodity Statistics and Information: 72. [1]. ^ Grobner T. (2006-01-23). "Gadolinium — a specific trigger for the development of nephrogenic fibrosing dermopathy and nephrogenic systemic fibrosis?". Nephrology Dialysis Transplantation 21 (4): 1104–8. doi:10.1093/ndt/gfk062. PMID 16431890. [edit] General referencesLos Alamos National Laboratory – Gadolinium[edit] External links Wikimedia Commons has media related to: Gadolinium Look up gadolinium inWiktionary, the free dictionary.WebElements.com – GadoliniumNephrogenic Systemic Fibrosis – Complication of Gadolinium MR ContrastIt's Elemental – Gadoliniumrefrigerator uses gadolinium metal that heats up when exposed to magnetic fieldFDA Advisory on Gadolinium-Based Contrastv • d • ePeriodic tableH HeLiBe BCNOFNeNaMg AlSiPSClArKCa ScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSr YZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaCePrNdPmSmEuGdTbDyHoErTmYbLuHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcThPaUNpPuAmCmBkCfEsFmMdNoLrRfDbSgBhHsMtDsRgUubUutUuqUupUuhUusUuoUueUbn Alkali metalsAlkaline earth metalsLanthanoidsActinoidsTransition metalsOther metalsMetalloidsOther nonmetalsHalogensNoble gasesRetrieved from "http://en.wikipedia.org/wiki/Gadolinium" Categories: Chemical elements | Element toxicology | Ferromagnetic materials | Lanthanides | Neutron poisons | Nuclear materials Views Article Discussion Edit this page History Personal tools Log in / create account if (window.isMSIE55) fixalpha(); Navigation Main page Contents Featured content Current events Random article Search Interaction About Wikipedia Community portal Recent changes Contact Wikipedia Donate to Wikipedia Help Toolbox What links here Related changesUpload fileSpecial pages Printable version Permanent linkCite this page Languages العربية বাংলা Беларуская Bosanski Български Català Česky Corsu Cymraeg Dansk Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Furlan Gaelg Galego 한국어 Հայերեն Hrvatski Ido Bahasa Indonesia Italiano עברית Basa Jawa Kreyòl ayisyen Latina Latviešu Lëtzebuergesch Lietuvių Lojban Magyar മലയാളം Nederlands 日本語 Norsk (bokmål) Norsk (nynorsk) Polski Português Русский Sicilianu Simple English Slovenčina Slovenščina Српски / Srpski Srpskohrvatski / Српскохрватски Suomi Svenska தமிழ் ไทย Tiếng Việt Türkçe Українська 中文   This page was last modified on 2 December 2008, at 14:36. 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