Ytterbium

0.13 %

{ syn. }

3.05%

14.3%

21.9%

16.12%

31.8%

{ syn. }

12.7%

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Ytterbium [ ʏtɛrbiʊm ] is a chemical element with the chemical symbol Yb and atomic number 70 in the periodic table it is in the group of lanthanides and also making it one of the metals of the rare earths. As with the other lanthanides ytterbium is a silvery heavy metal. The properties of the lanthanide ytterbium not follow, and due to its electronic configuration the element has a significantly lower density and a lower melting point and boiling point than the adjacent elements.

Ytterbium was discovered in 1878 by Jean Charles de Galissard Marignac in the investigation of Gadolinit. 1907 Georges Urbain separated, Carl Auer von Welsbach and Charles James independently from another element lutetium, ytterbium of Marignacs. The previous name was there against the wishes of Catfish creek, which had proposed aldebaranium maintained after prolonged discussion.

Technically, the element and its compounds are used, due to the complex separation of the other lanthanides in only small quantities, inter alia, as a dopant for yttrium aluminum garnet laser. Ytterbium (III ) chloride and ytterbium ( II) iodide, reagents in various organic synthesis reactions.

8.1 halides
8.2 Organometallic Compounds
8.3 Other compounds

History

Ytterbium was discovered in 1878 by Swiss chemist Jean Charles de Galissard Marignac. He examined Gadolinit accurate and tried by decomposition of nitrates to separate the insoluble erbium from the other mineral components in hot water. He discovered that the crystals obtained are not uniform consisted of red erbium nitrate, but remained more colorless crystals. The measured absorption spectrum showed that there must be either crystals of a previously unknown element. This he named after the archaeological site of Gadolinites in Ytterby ( Sweden) and because of the similarity to the yttrium ytterbium. Separation of the two elements was achieved in another experiment by the addition of acid to a solution of hyposchwefliger chlorides.

1907 saw the Frenchman Georges Urbain independently, the Austrian Carl Auer von Welsbach and the American Charles James, that the ytterbium found Marignac is not a pure element, but is a mixture of two elements. You could separate this mixture into the now pure ytterbium and lutetium in. It called Carl Auer von Welsbach the elements aldebaranium ( after the star Aldebaran ) and Cassiopeium while Urbain Neoytterbium and lutetium stipulated as the name. In 1909, the international atomic weight Committee, consisting of Frank Wigglesworth Clarke, Wilhelm Ostwald, Thomas Edward Thorpe and Georges Urbain, determined that Urbain entitled to the discovery of lutetium and thus also designated by him in their name. However, it was maintained for the ytterbium the old name Marignacs.

Elemental ytterbium was first obtained in 1936 by Heinrich Wilhelm Klemm and Bommer. They won the metal by reduction of ytterbium ( III) chloride at 250 ° C. with potassium Further, they determined the crystal structure and the magnetic properties of the metal.

Occurrence

Ytterbium is a rare element on Earth, its abundance in the Earth's continental crust is about 3.2 ppm.

Ytterbium is found as a component of rare earth minerals, especially those of yttrium and the heavier lanthanides such as xenotime and Gadolinit. So xenotime contains from Malaysia up to 6.2 % ytterbium. Ceriterden as monazite and Bastnäsit hand, contain lower levels of ytterbium, so depending on the deposit contains monazite from 0.12 to 0.5 % of the element.

There are several rare minerals known in which ytterbium is the most common rare earth metal. These include xenotime - (Yb ) with a share of 32 percent by weight of Ytterbium on the mineral and the ratio formula ( b0, 40Y0, 27Lu0, 12Er0, 12Dy0, 05Tm0, 04Ho0, 01) PO4 and Keiviit - (Yb ) with the ratio formula ( Yb 1, 43Lu0, 23Er0, 17Tm0, 08Y0, 05Dy0, 03Ho0, 02) 2Si2O7. These minerals are each parts of a solid solution, from the other naturally occurring compositions, especially with yttrium as a main component are well known.

The major sources of ytterbium are the monazite and Xenotimvorkommen in China and Malaysia ( there as an accessory mineral of cassiterite ). Due to the low demand, the situation of supply of ytterbium is not considered critical.

Production and representation

The extraction of ytterbium is complicated and lengthy, especially through the difficult separation of the lanthanides. The output of minerals such as monazite or xenotime are first digested with acids or alkalis and brought into solution. The separation of ytterbium from the other lanthanides is then possible by various methods, the separation by means of ion exchange, the technically most important method for ytterbium, as well as other rare lanthanoids group. The solution is applied with the rare earths to a suitable resin to which the individual lanthanide ions bind to different degrees. Then it is dissolved in a separation column by means of chelating agents such as EDTA, DTPA or HEDTA from the resin, and the varying degrees of binding to the resin thus obtained to the separation of individual lanthanides.

A chemical separation is possible by different responses of ytterbium, lutetium, and Thuliumacetat with sodium amalgam. This ytterbium forms an amalgam, while the lutetium and Thuliumverbindungen not respond.

The metal production by electrolysis of ytterbium can be a melt of ytterbium (III ) fluoride, and ytterbium (III ) chloride, with an alkali - or alkaline earth metal to the melting point reduction, and liquid cadmium or zinc as a cathode. In addition, it can also be by metallothermal reduction of ytterbium (III ) fluoride with calcium, or manufacture of ytterbium ( III ) oxide with lanthanum or cerium. The final reaction is carried out in a vacuum, ytterbium is distilled off and can thus be separated from the other lanthanides.

Properties

Physical Properties

Ytterbium is like the other lanthanides a silvery, soft metal heavy. It has 6.973 g/cm3 with an unusually low density, which is significantly lower than that of the adjacent lanthanides such as thulium and lutetium and is comparable to that of neodymium or praseodymium. The same applies for the relatively low melting point of 824 ° C and the boiling point of 1196 ° C ( lutetium: Melting point 1652 ° C, boiling point 3,402 ° C). These values are contrary to the otherwise applicable lanthanide and are caused by the electron configuration [ Xe] 4f14 6s2 ytterbium. Due to the completely filled f shell are only two valence electrons for metallic bonds available and therefore there is less binding ability and to a much larger metal atom radius.

There are known three different crystal structures at atmospheric pressure and three other high-pressure modifications of the ytterbium. At room temperature the metal crystallizes in a cubic closest packing of spheres with the lattice parameters a = 548.1 pm. At higher temperatures and pressures, this structure merges into a body-centered cubic sphere packing, wherein the transition temperature is at atmospheric pressure at about 770 ° C and at room temperature, the transition pressure at 4 GPa. At low temperatures, a hexagonal closest structure is stable, the structural phase transition, which lies between 0 and 45 ° C, is strongly dependent on purity, pressure and stresses in the metal. These phases have different magnetism. While the hexagonal phase (as expected from the fully occupied orbitals ) is diamagnetic, the face-centered cubic structure paramagnetism shows (probably by small amounts of Yb3 in the metal).

The order of the high-pressure modifications does not match the frequently to be found in other lanthanides order. Thus, no modifications of the ytterbium with a double - hexagonal closest- structure or a samarium structure are known. On the from 4 GPa stable body-centered cubic structure follows a hexagonal closest phase at 26 GPa. The next phase transition takes place upon further increase in pressure at 53 GPa and above this pressure, in turn, forms a cubic closest structure. Another well-known phase transition occurs at 98 GPa. From this pressure is up to at least 202 GPa a hexagonal structure the most stable, with the space group P3121 ( HP3- structure). The pressure increase is a change in the electron structure of the ytterbium, wherein an electron from the f orbital is converted into a d- orbital, and the electron configuration is then, as with other trivalent lanthanides ( trivalent).

Chemical Properties

Ytterbium is a typical non-noble metal, which reacts primarily at higher temperatures with most non-metals. Reacts slowly with oxygen at standard conditions of dry air, faster in the presence of moisture. Finely divided metal is ytterbium, as other base metals, air and oxygen flammable. Mixtures of finely divided ytterbium and organohalogen compounds such as hexachloroethane or polytetrafluoroethylene burn with emerald- green flame. The reaction of hydrogen with ytterbium is not complete, because the hydrogen enters into the octahedral sites of the metal structure and are formed of non-stoichiometric hydride phase, where the composition of the temperature and the hydrogen pressure depends.

In water, Ytterbium dissolves slowly in acids rapidly to form hydrogen. In solution, most are trivalent, colorless ytterbium ions in the form of the hydrate [ Yb (H2O ) 9] 3 before. The yellow-green divalent ytterbium ion is not stable in aqueous solution, it oxidizes to form hydrogen with a half-life of about 2.8 hours to the trivalent ion. If ytterbium dissolved in liquid ammonia, forms like sodium solvated electrons by a blue solution.

Isotopes

There are a total of 33 known isotopes 148Yb and 181Yb between and another 12 Kernisomere ytterbium. Of these, seven are found in nature with varying frequency. The isotope with the largest share of the natural isotopic composition 174Yb with a share of 31.8 %, followed by 21.9% with 172Yb, 173Yb with 16.12%, 171Yb and 176Yb with 14.3% with 12.7%. 170Yb and 168Yb are at levels of 3.05 and 0.13 % significantly less.

The radioactive isotope 169Yb with a half-life of 32 days is formed together with the short-lived 175Yb (half-life 4.2 days ) by neutron activation in the irradiation of ytterbium in nuclear reactors. It can be used as gamma-ray source, such as in nuclear medicine and radiography, are used.

Use

Ytterbium and its compounds are used commercially only in a very limited extent. As an alloying component, it improves the grain refining, strength, and mechanical properties of the stainless steel. It has been studied to use Ytterbiumlegierungen in dentistry.

Ytterbium as other lanthanide as a dopant for yttrium aluminum garnet laser (Yb: YAG laser ) is used. Advantages over Nd: YAG lasers are the higher possible maximum doping, a longer lifetime of the higher energy levels and greater absorption bandwidth. In fiber lasers is an important Ytterbium dopant may be used due to similar advantages as in the YAG laser in particular for high-performance fiber laser. These include the high doping, a large absorption range 850-1070 nm and also the large emission range 970-1200 nm

Experimentally ytterbium was investigated as an alternative to cesium for operating atomic clocks. It was four times as high accuracy as measured at a cesium atomic clock.

Ytterbium is being investigated as a substitute for magnesium in severe active charges for kinematic Infrarottäuschkörper. This is due to a significantly higher ytterbium emissivity of ytterbium ( III) oxide in the infrared region as compared to magnesium oxide, a higher radiation power than conventional active materials based on magnesium / teflon / viton ( MTV ).

Biological significance and toxicity

Ytterbium is found only in minimal amounts in the body and has no biological significance. Only a few organisms such as lichens are able to receive ytterbium, and have Ytterbiumgehalte of about 900 ppb. In brown algae ( Sargassum polycystum ) a biosorption of 0.7 to 0.9 mmol · g -1 was measured.

Ytterbium and its soluble compounds are mildly toxic, for ytterbium (III ) chloride, a LD50 value of 395 mg / kg for intraperitoneal and 6700 mg / kg for oral administration was determined in mice. In animal experiments on rabbits ytterbium chloride is irritating to eyes and skin only slightly only in case of injuries. Ytterbium is considered to be teratogenic; in a study of Syrian hamster embryo as grown together or additional ribs or spinal changes were observed following administration of ytterbium skeletal changes.

Compounds

These are compounds of ytterbium in the oxidation state 2 and 3 known, as in all lanthanides 3 is the more common and more stable level.

Halides

The halogens fluorine, chlorine, bromine and iodine ytterbium forms two series of salts having the formulas and YbX2 YbX3. The dihalides oxidize it easy to trihalides, at higher temperatures they undergo disproportionation to Ytterbiumtrihalogeniden and ytterbium.

Several Ytterbiumhalogenide be used as a reagent in organic synthesis. As ytterbium ( III) chloride is a Lewis acid and may be used as a catalyst for example in aldol reactions, Diels-Alder reactions or allylation. Ytterbium ( II) iodide may be such as samarium ( II) iodide to be used for the coupling reaction as a reducing agent or.

Ytterbium (III ) fluoride is used as an inert and non- toxic filler in dentistry. It continually sets the important for dental health fluoride free and is also a good x-ray contrast agent.

Organometallic Compounds

There are known a number of organometallic compounds. Compounds with a sigma bond between ytterbium and carbon are known only to a small extent, as it comes easily to subsequent reactions such as β - Hydrideliminierungen in this as in many transition metals. They are, therefore, with bulky residues such as the tert- butyl group, or a larger number of smaller groups such as in a Hexamethylytterbat complex [ Yb ( CH3) 6] 3 stable. The main ligands of ytterbium are cyclopentadienyl and derivatives thereof. Sandwich complexes of ytterbium are not known with cyclopentadienyl, but only with larger ligands such as pentaphenylcyclopentadienyl. Furthermore, one knows complexes with η5 coordinated cyclopentadienyl ligands: CpYbX2, Cp2YbX and Cp3Yb (X can halide, hydride, alkoxide or another be ).