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Ytterbium is a chemical element; it has symbol Yb and atomic number 70. It is a metal, the fourteenth element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. Like the other lanthanides, its most common oxidation state is +3, as in its oxide, , and other compounds. In aqueous solution, like compounds of other late lanthanides, soluble ytterbium compounds form complexes with nine water molecules. Because of its closed-shell electron configuration, its density, melting point and boiling point are much lower than those of most other lanthanides.
In 1878, Swiss chemist Jean Charles Galissard de Marignac separated from the rare earth "erbia", another independent component, which he called "ytterbia", for Ytterby, the village in Sweden near where he found the new component of erbium. He suspected that ytterbia was a compound of a new element that he called "ytterbium". Four elements were named after the village, the others being yttrium, terbium, and erbium. In 1907, the new earth "lutecia" was separated from ytterbia, from which the element "lutecium", now lutetium, was extracted by Georges Urbain, Carl Auer von Welsbach, and Charles James. After some discussion, Marignac's name "ytterbium" was retained. A relatively pure sample of the metal was first obtained in 1953. At present, ytterbium is mainly used as a dopant of stainless steel or active laser media, and less often as a gamma ray source.
Natural ytterbium is a mixture of seven stable isotopes, which altogether are present at an average concentration of 0.3 parts per million in the Earth's crust. This element is mined in China, the United States, Brazil, and India in form of the minerals monazite, euxenite, and xenotime. The ytterbium concentration is low because it is found only among many other rare-earth elements. It is among the least abundant. Once extracted and prepared, ytterbium is somewhat hazardous as an eye and skin irritant. The metal is a fire and explosion hazard.
Ytterbium has three Allotropy labeled by the Greek letters alpha, beta and gamma. Their transformation temperatures are −13 °Celsius and 795 °C, although the exact transformation temperature depends on the pressure and stress. The beta allotrope (6.966 g/cm3) exists at room temperature, and it has a face-centered cubic crystal structure. The high-temperature gamma allotrope (6.57 g/cm3) has a body-centered cubic crystalline structure. The alpha allotrope (6.903 g/cm3) has a hexagonal crystalline structure and is stable at low temperatures.
The beta allotrope has a metallic electrical conductivity at normal atmospheric pressure, but it becomes a semiconductor when exposed to a pressure of about 16,000 atmospheres (1.6 gigapascal). Its electrical resistivity increases ten times upon compression to 39,000 atmospheres (3.9 GPa), but then drops to about 10% of its room-temperature resistivity at about 40,000 atm (4.0 GPa).
In contrast to the other rare-earth metals, which usually have antiferromagnetic and/or ferromagnetic properties at low , ytterbium is paramagnetic at temperatures above 1.0 kelvin.Jackson, M. (2000). "Magnetism of Rare Earth". The IRM quarterly 10(3): 1 However, the alpha allotrope is diamagnetic. With a melting point of 824 °C and a boiling point of 1196 °C, ytterbium has the smallest liquid range of all the metals.
Contrary to most other lanthanides, which have a close-packed hexagonal lattice, ytterbium crystallizes in the face-centered cubic system. Ytterbium has a density of 6.973 g/cm3, which is significantly lower than those of the neighboring lanthanides, thulium (9.32 g/cm3) and lutetium (9.841 g/cm3). Its melting and boiling points are also significantly lower than those of thulium and lutetium. This is due to the closed-shell electron configuration of ytterbium (Xe 4f14 6s2), which causes only the two 6s electrons to be available for metallic bonding (in contrast to the other lanthanides where three electrons are available) and increases ytterbium's metallic radius.
Ytterbium is quite electropositive, and it reacts slowly with cold water and quite quickly with hot water to form ytterbium(III) hydroxide:
Ytterbium reacts with all the :
The ytterbium(III) ion absorbs light in the near-infrared range of wavelengths, but not in visible light, so ytterbia, Yb2O3, is white in color and the salts of ytterbium are also colorless. Ytterbium dissolves readily in dilute sulfuric acid to form solutions that contain the colorless Yb(III) ions, which exist as nonahydrate complexes:
The known isotopes of ytterbium range from 149Yb to 187Yb. The primary decay mode for those isotopes lighter than the most abundant stable isotope, 174Yb, is electron capture giving thulium isotopes; the primary mode after is beta emission giving lutetium isotopes.
As an even-numbered lanthanide, in accordance with the Oddo–Harkins rule, ytterbium is significantly more abundant than its immediate neighbors, thulium and lutetium, which occur in the same concentrate at levels of about 0.5% each. The world production of ytterbium is only about 50 tonnes per year, reflecting that it has few commercial applications. Microscopic traces of ytterbium are used as a dopant in the , a solid-state laser in which ytterbium is the element that undergoes stimulated emission of electromagnetic radiation.
Ytterbium is often the most common substitute in yttrium minerals. In very few known cases/occurrences ytterbium prevails over yttrium, as, e.g., in xenotime-(Yb). A report of native ytterbium from the Moon's regolith is known.
Ytterbium is separated from other rare earths either by ion exchange or by reduction with sodium amalgam. In the latter method, a buffered acidic solution of trivalent rare earths is treated with molten sodium-mercury alloy, which reduces and dissolves Yb3+. The alloy is treated with hydrochloric acid. The metal is extracted from the solution as oxalate and converted to oxide by heating. The oxide is reduced to metal by heating with lanthanum, aluminium, cerium or zirconium in high vacuum. The metal is purified by sublimation and collected over a condensed plate.
Some ytterbium halides are used as in organic synthesis. For example, ytterbium(III) chloride (YbCl3) is a Lewis acid and can be used as a catalyst in the Aldol reaction and Diels–Alder reactions. Ytterbium(II) iodide (YbI2) may be used, like samarium(II) iodide, as a reducing agent for coupling reactions. Ytterbium(III) fluoride (YbF3) is used as an inert and non-toxic tooth filling as it continuously releases fluoride ions, which are good for dental health, and is also a good X-ray contrast agent.Enghag, Per (2004). Encyclopedia of the elements: technical data, history, processing, applications. John Wiley & Sons, , p. 448.
In 1907, the French chemist Georges Urbain separated Marignac's ytterbia into two components: neoytterbia and lutecia. Neoytterbia later became known as the element ytterbium, and lutecia became known as the element lutetium. The Austrian chemist Carl Auer von Welsbach independently isolated these elements from ytterbia at about the same time, but he called them aldebaranium ( Ad; after Aldebaran) and cassiopeium. The American chemist Charles James also independently isolated these elements at about the same time.
Urbain and Welsbach accused each other of publishing results based on the other party. In 1909, the Commission on Atomic Mass, consisting of Frank Wigglesworth Clarke, Wilhelm Ostwald, and Georges Urbain, which was then responsible for the attribution of new element names, settled the dispute by granting priority to Urbain and adopting his names as official ones, based on the fact that the separation of lutetium from Marignac's ytterbium was first described by Urbain. After Urbain's names were recognized, neoytterbium was reverted to ytterbium.
The chemical and physical properties of ytterbium could not be determined with any precision until 1953, when the first nearly pure ytterbium metal was produced by using ion-exchange processes. The price of ytterbium was relatively stable between 1953 and 1998 at about US$1,000/kg.
Visible light waves oscillate faster than microwaves, hence optical clocks can be more precise than caesium atomic clocks. The Physikalisch-Technische Bundesanstalt is working on several such optical clocks. The model with one single ytterbium ion caught in an ion trap is highly accurate. The optical clock based on it is exact to 17 digits after the decimal point.Peik, Ekkehard (2012-03-01). New "pendulum" for the ytterbium clock. ptb.de.
The kinetic of excitations in ytterbium-doped materials is simple and can be described within the concept of effective cross-sections; for most ytterbium-doped laser materials (as for many other optically pumped gain media), the McCumber relation holds, although the application to the ytterbium-doped composite materials was under discussion.
Usually, low concentrations of ytterbium are used. At high concentrations, the ytterbium-doped materials show photodarkening (glass fibers) or even a switch to broadband emission (crystals and ceramics) instead of efficient laser action. This effect may be related with not only overheating, but also with conditions of charge compensation at high concentrations of ytterbium ions.
Much progress has been made in the power scaling lasers and amplifiers produced with ytterbium (Yb) doped optical fibers. Power levels have increased from the 1 kW regimes due to the advancements in components as well as the Yb-doped fibers. Fabrication of Low NA, Large Mode Area fibers enable achievement of near perfect beam qualities (M2<1.1) at power levels of 1.5 kW to greater than 2 kW at ~1064 nm in a broadband configuration. Ytterbium-doped LMA fibers also have the advantages of a larger mode field diameter, which negates the impacts of nonlinear effects such as stimulated Brillouin scattering and stimulated Raman scattering, which limit the achievement of higher power levels, and provide a distinct advantage over single mode ytterbium-doped fibers.
To achieve even higher power levels in ytterbium-based fiber systems, all factors of the fiber must be considered. These can be achieved only through optimization of all ytterbium fiber parameters, ranging from the core background losses to the geometrical properties, to reduce the splice losses within the cavity. Power scaling also requires optimization of matching passive fibers within the optical cavity. The optimization of the ytterbium-doped glass itself through host glass modification of various dopants also plays a large part in reducing the background loss of the glass, improvements in slope efficiency of the fiber, and improved photodarkening performance, all of which contribute to increased power levels in 1 μm systems.
Currently, ytterbium is being investigated as a possible replacement for magnesium in high density pyrotechnic payloads for kinematic infrared decoy flares. As ytterbium(III) oxide has a significantly higher emissivity in the infrared range than magnesium oxide, a higher radiant intensity is obtained with ytterbium-based payloads in comparison to those commonly based on magnesium/Teflon/Viton (MTV).
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