Ytterbium

Ytterbium is a chemical element with the symbol Yb and atomic number 70. A soft silvery metallic element, ytterbium is a rare earth element of the lanthanide series and is found in the minerals gadolinite, monazite, and xenotime. The element is sometimes associated with yttrium or other related elements and is used in certain steels. Natural ytterbium is a mix of seven stable isotopes. Ytterbium-169, an artificially produced isotope, is used as a gamma ray source.
Characteristics

Physical

Ytterbium is a soft, malleable and rather ductile element that exhibits a bright silvery luster. A rare earth element, it is easily attacked and dissolved by mineral acids, slowly reacts with water, and oxidizes in air.[2]

Ytterbium has three allotropes which are called alpha, beta and gamma and whose transformation points are at −13 °C and 795 °C. The beta form exists at room temperature and has a face-centered crystal structure while the high-temperature gamma form has a body-centered crystal structure.[2]

Normally, the beta form has a metallic-like electrical conductivity, but becomes a semiconductor when exposed to around 16,000 atm (1.6 GPa). Its electrical resistivity is tenfold larger at about 39,000 atm (3.9 GPa) but then drops dramatically, to around 10% of its room temperature resistivity value, at 40,000 atm (4 GPa).[2][3]

Contrary to other rare-earth metals, which show antiferromagnetic or/and ferromagnetic ordering at low temperatures, Yb is paramagnetic at any temperatures above 1 K.[4]

With the melting point of 824°C and the boiling point of 1196°C, it is the narrowest ranges of its liquid state of any metal.

Chemical

Ytterbium metal tarnishes slowly in air and burns readily at 200 °C to form ytterbium(III) oxide (Yb2O3) or less stable ytterbium monoxide (YbO).

Ytterbium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form ytterbium hydroxide:

2 Yb (s) + 6 H2O (l) → 2 Yb(OH)3 (aq) + 3 H2 (g)

Ytterbium metal reacts with all the halogens:

2 Yb (s) + 3 F2 (g) → 2 YbF3 (s) [white]
2 Yb (s) + 3 Cl2 (g) → 2 YbCl3 (s) [white]
2 Yb (s) + 3 Br2 (g) → 2 YbBr3 (s) [white]
2 Yb (s) + 3 I2 (g) → 2 YbI3 (s) [white]

Ytterbium(III) ion absorbs light in the near infrared spectral range, but not in the visible region, so that ytterbia is white, and ytterbium salts of colorless anions are also colorless. Ytterbium dissolves readily in dilute sulfuric acid to form solutions containing the colorless Yb(III) ions, which exist as a [Yb(OH2)9]3+ complexes:[5]

2 Yb (s) + 3 H2SO4 (aq) → 2 Yb3+ (aq) + 3 SO2−4 (aq) + 3 H2 (g)

Compounds

Ytterbium shows similar chemical behavior to the rest of the lanthanide group. Most of the compounds are found in the oxidation state +3, the salts in that oxidation state are nearly colorless. Like europium, samarium or thulium trihalogenes can be reduced by hydrogen or by addition of the metal reduced to the dihalogens, in this case the for example YbCl2. The oxidation state +2 reacts in some ways similarly to the alkaline earth metal compounds, for example the Ytterbium(II) oxide (YbO) shows the same structure as calcium oxide (CaO).[6]

* Halides: YbCl2, YbBr3, YbCl3, YbF3
* Oxides: Yb2O3

See also: Category:Ytterbium compounds

Isotopes
Main article: Isotopes of ytterbium

Naturally-occurring ytterbium is composed of 7 stable isotopes: Yb-168, Yb-170, Yb-171, Yb-172, Yb-173, Yb-174, and Yb-176, with Yb-174 being the most abundant (31.83% natural abundance). 27 radioisotopes have been characterized, with the most stable being Yb-169 with a half-life of 32.026 days, Yb-175 with a half-life of 4.185 days, and Yb-166 with a half-life of 56.7 hours. All of the remaining radioactive isotopes have half-lives that are less than 2 hours, and the majority of these have half-lives that are less than 20 minutes. This element also has 12 meta states, with the most stable being Yb-169m (t½ 46 seconds).

The isotopes of ytterbium range in atomic weight from 147.9674 u (Yb-148) to 180.9562 u (Yb-181). The primary decay mode before the most abundant stable isotope, Yb-174 is electron capture, and the primary mode after is beta emission. The primary decay products before Yb-174 are element 69 (thulium) isotopes, and the primary products after are element 71 (lutetium) isotopes. Of interest to modern quantum optics, the different ytterbium isotopes follow either Bose-Einstein statistics or Fermi-Dirac statistics, leading to interesting behavior in optical lattices.

History

Ytterbium was discovered by the Swiss chemist Jean Charles Galissard de Marignac in the year 1878. Marignac found a new component in the earth then known as erbia and named it ytterbia (after Ytterby, the Swedish village where he found the new erbia component). He suspected that ytterbia was a compound of a new element he called ytterbium.[3]

In 1907, the French chemist Georges Urbain separated Marignac's ytterbia into two components: neoytterbia and lutecia. Neoytterbia would later become known as the element ytterbium, and lutecia would later be known as the element lutetium. Auer von Welsbach independently isolated these elements from ytterbia at about the same time, but called them aldebaranium and cassiopeium.[3]

The chemical and physical properties of ytterbium could not be determined until 1953, when the first nearly pure ytterbium was produced.[3] The price of ytterbium was relatively stable between 1953 and 1998 at about US$ 1,000/kg.[7]

Occurrence
Euxenite

Ytterbium is found with other rare earth elements in several rare minerals. It is most often recovered commercially from monazite sand (0.03% ytterbium). The element is also found in euxenite and xenotime. The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia; and reserves of ytterbium are estimated as about one million tonnes. Ytterbium is normally difficult to separate from other rare earths, but ion-exchange and solvent extraction techniques developed in the mid to late 20th century have simplified separation. Known compounds of ytterbium are rare—they haven't been well characterized yet. The abundance of ytterbium in the Earth crust is about 3 mg/kg.[3]

The most important current (2008) sources of ytterbium are the ionic adsorption clays of southern China. The "High Yttrium" concentrate derived from some versions of these comprise about two thirds yttria by weight, and 3-4% ytterbia. 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 the fact that it finds little commercial application.[3]

Production

Recovery of ytterbium from ores involves several processes which are common to most rare-earth elements: 1) processing, 2) separation of Yb from other rare earths, 3) preparation of the metal. If the starting ore is gadolinite, it is digested with hydrochloric or nitric acid which dissolves the rare-earth metals. The solution is treated with sodium oxalate or oxalic acid to precipitate rare earths as oxalates. For euxenite, or is processed either by fusion with potassium bisulfate or with hydrofluoric acid. Monazite or xenotime are heated either with sulfuric acid or with caustic soda.

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.[8]

Applications

Source of gamma rays

The 169Yb isotope has been used as a radiation source substitute for a portable X-ray machine when electricity was not available. Like X-rays, gamma rays pass through soft tissues of the body, but are blocked by bones and other dense materials. Thus, small 169Yb samples (which emit gamma rays) act like tiny X-ray machines useful for radiography of small objects. Experiment shows that radiographs taken with 169Yb source are roughly equivalent to those taken with X-rays having energies between 250 and 350 keV.[9]

Doping of stainless steel

Ytterbium could also be used to help improve the grain refinement, strength, and other mechanical properties of stainless steel. Some ytterbium alloys have been used in dentistry.[2][3]

Yb as dopant of active media

Yb is used as dopant in optical materials, usually in the form of ions in active laser media. Several powerful double-clad fiber lasers and disk lasers use Yb3+ ions as dopant at concentration of several atomic percent. Glasses (optical fibers), crystals and ceramics with Yb3+ are used.[10]

Ytterbium is often used as a doping material (as Yb3+) for high power and wavelength-tunable solid state lasers. Yb lasers commonly radiate in the 1.06–1.12 µm band being optically pumped at wavelength 900 nm–1 µm, dependently on the host and application. Small quantum defect makes Yb prospective dopant for efficient lasers and power scaling.[11]

The kinetic of excitations in Yb-doped materials is simple and can be described within concept of effective cross-sections; for the most of Yb-doped laser materials (as for many other optically-pumped gain media), the McCumber relation holds,[10][12][13] although the application to the Yb-doped composite materials was under discussion.[14][15]

Usually, low concentrations of Yb are used. At high concentration of excitations, the Yb-doped materials show photodarkening[16] (glass fibers) or ever switch to the broadband emission [17] (crystals and ceramics) instead of the efficient laser action. This effect may be related with not only overheating, but also conditions of the charge compensation at high concentration of Yb ions.[18]

Others

Ytterbium metal increases its electrical resistivity when subjected to high stresses. This property is used in stress gauges to monitor ground deformations from earthquakes and explosions.[19]

Precautions

Although ytterbium is fairly stable, it nevertheless should be stored in closed containers to protect it from air and moisture. All compounds of ytterbium should be treated as highly toxic although initial studies appear to indicate that the danger is limited. Ytterbium compounds are, however, known to cause skin and eye irritation and may be teratogenic.[20] Metallic ytterbium dust poses a fire and explosion hazard.[21]

See also

* Erbium
* Terbium
* Yttrium

References

1. ^ M. Jackson "Magnetism of Rare Earth" The IRM quarterly col. 10, No. 3, p. 1, 2000
2. ^ a b c d C. R. Hammond (2000). The Elements, in Handbook of Chemistry and Physics 81st edition. CRC press. ISBN 0849304814.
3. ^ a b c d e f g John Emsley (2003). Nature's building blocks: an A-Z guide to the elements. Oxford University Press. pp. 492–494. ISBN 0198503407. http://books.google.co.jp/books?id=j-Xu07p3cKwC.
4. ^ M. Jackson "Magnetism of Rare Earth" The IRM quarterly col. 10, No. 3, p. 1, 2000
5. ^ "Chemical reactions of Ytterbium". Webelements. https://www.webelements.com/ytterbium/chemistry.html. Retrieved 2009-06-06.
6. ^ Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils; (1985). "Die Lanthanoide" (in German). Lehrbuch der Anorganischen Chemie (91–100 ed.). Walter de Gruyter. pp. 1265–1279. ISBN 3-11-007511-3.
7. ^ James B. Hedrick. "Rare-Earth Metals". USGS. http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/740798.pdf. Retrieved 2009-06-06.
8. ^ Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 973–975. ISBN 0070494398. http://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA243. Retrieved 2009-06-06.
9. ^ R. Halmshaw (1995). Industrial radiology: theory and practice. Springer. pp. 168–169. ISBN 0412627809. http://books.google.co.jp/books?id=wJqBSA1exqoC&.
10. ^ a b D. Kouznetsov; J.-F. Bisson, K. Takaichi, K. Ueda (2005). "Single-mode solid-state laser with short wide unstable cavity". JOSAB 22 (8): 1605–1619. doi:10.1364/JOSAB.22.001605. http://josab.osa.org/abstract.cfm?id=84730.
11. ^ Grukh, Dmitrii A (2004). "Broadband radiation source based on an ytterbium-doped fibre with fibre-length-distributed pumping". Quantum Electronics 34: 247. doi:10.1070/QE2004v034n03ABEH002621.
12. ^ D. E. McCumber (1964). "Einstein relations connecting broadband emission and absorption spectra". Physical Review B 136 (4A): 954–957. doi:10.1103/PhysRev.136.A954.
13. ^ P. C. Becker, N. A. Olson, J. R. Simpson. (1999). Erbium-doped fiber amplifiers: fundamentals and theory. Academic press.
14. ^ D. Kouznetsov (2007). "Comment on Efficient diode-pumped Yb:Gd2SiO5 laser". Applied Physics Letters 90: 066101. doi:10.1063/1.2435309.
15. ^ Guangjun Zhao; Liangbi Su, Jun Xu, Heping Zeng (2007). "Response to Comment on Efficient diode-pumped Yb:Gd2SiO5 laser". Applied Physics Letters 90: 066103. doi:10.1063/1.2435314.
16. ^ Joona J. Koponen; Mikko J. Söderlund, Hanna J. Hoffman, and Simo K. T. Tammela (2006). "Measuring photodarkening from single-mode ytterbium doped silica fibers". Optics Express 14 (24): 11539–11544. doi:10.1364/OE.14.011539.
17. ^ J.-F. Bisson; D. Kouznetsov, K. Ueda, S. T. Fredrich-Thornton, K. Petermann, G. Huber (2007). "Switching of emissivity and photoconductivity in highly doped Yb3+:Y2O3 and Lu2O3 ceramics". Applied Physics Letters 90: 201901. doi:10.1063/1.2739318.
18. ^ N. V. Sochinskii; M. Abellan, J. Rodriguez-Fernandez, E. Saucedo, C. M. Ruiz, V. Bermudez (2007). "Effect of Yb concentration on the resistivity and lifetime of CdTe:Ge:Yb codoped crystals". Applied Physics Letters 91 (20): 202112. doi:10.1063/1.2815644.
19. ^ C. K. Gupta, Nagaiyar Krishnamurthy (2004). Extractive metallurgy of rare earths. CRC Press. p. 32. ISBN 0415333407. http://books.google.co.jp/books?id=F0Bte_XhzoAC&pg=PA32.
20. ^ Gale, Tf (Jun 1975). "The embryotoxicity of ytterbium chloride in golden hamsters.". Teratology 11 (3): 289–95. doi:10.1002/tera.1420110308. ISSN 0040-3709. PMID 807987.
21. ^ "Material safety data sheet". http://www.espi-metals.com/msds%27s/ytterbium.pdf. Retrieved 2009-06-06.