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.
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).
Ytterbium is one of the lanthanides that is able to become divalent. Like the other potentially divalent lanthanides, samarium and europium, it is capable of being extracted into mercury by the use of sodium amalgam, which made it one of the easier lanthanides to purify using classical techniques. However, this divalency was not discovered until the 20th century.
Ytterbium(III) ion absorbs light in the near infra-red, but not in the visible region, so that ytterbia is white, and ytterbium salts of colorless anions are also colorless.
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.
The chemical and physical properties of ytterbium could not be determined until 1953 when the first nearly pure ytterbium was produced.
Ytterbium oxide first became commercially available in significant quantities the mid to late 1950's, as a result of the development of ion-exchange separation technology using EDTA as eluting agent, and copper(II) as the retaining ion, which was invented at Iowa State University's Ames Laboratory by Frank Spedding and co-workers. In a price list dated January 20, 1959, the Lindsay Chemical Division of American Potash and Chemical Corporation, which at the time was the largest producer of rare earths in the world, was offering 99% ytterbium oxide at 160 dollars per pound, and their 99.9% grade at 200 dollars per pound. The minimum order quantity was 5 grams, priced at 70 or 90 cents per gram, respectively. In modern times, kilogram quantities of ytterbium oxide have been available from specialists in rare earths priced between 100 and 200 dollars per kilogram.
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 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.
Yb is used as dopant in optics 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.
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 1.06–1.12µm band being optically pumped at wavelength 900nm–1µm, dependently on the host and application. Small quantum defect makes Yb prospective dopant for efficient lasers and power scaling.
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 , although the application to the Yb-doped composite materials was under discussion .
Usually, low concentrations of Yb are used. At high concentration of excitations, the Yb-doped materials show photodarkening (glass fibers) or ever switch to the broadband emission (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.