Erbium

2008/9 Schools Wikipedia Selection. Related subjects: Chemical elements

68 holmium ← erbium → thulium - ↑ Er ↓ Fm Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	erbium, Er, 68
Chemical series	lanthanides
Group, Period, Block	n/a, 6, f
Appearance	silvery white
Standard atomic weight	167.259 (3)  g·mol−1
Electron configuration	[Xe] 4f12 6s²
Electrons per shell	2, 8, 18, 30, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	9.066  g·cm−3
Liquid density at m.p.	8.86  g·cm−3
Melting point	1802  K (1529 ° C, 2784 ° F)
Boiling point	3141  K (2868 ° C, 5194 ° F)
Heat of fusion	19.90   kJ·mol−1
Heat of vaporization	280   kJ·mol−1
Specific heat capacity	(25 °C) 28.12  J·mol−1·K−1
Vapor pressure P(Pa) 1 10 100 1 k 10 k 100 k at T(K) 1504 1663 (1885) (2163) (2552) (3132)
Atomic properties
Crystal structure	hexagonal
Oxidation states	3 ( basic oxide)
Electronegativity	1.24 (Pauling scale)
Ionization energies ( more)	1st:  589.3   kJ·mol−1
	2nd:  1150  kJ·mol−1
	3rd:  2194  kJ·mol−1
Atomic radius	175   pm
Atomic radius (calc.)	226  pm
Miscellaneous
Magnetic ordering	no data
Electrical resistivity	( r.t.) (poly) 0.860 µΩ·m
Thermal conductivity	(300 K) 14.5  W·m−1·K−1
Thermal expansion	( r.t.) (poly) 12.2 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 2830 m/s
Young's modulus	69.9  GPa
Shear modulus	28.3  GPa
Bulk modulus	44.4  GPa
Poisson ratio	0.237
Vickers hardness	589  MPa
Brinell hardness	814  MPa
CAS registry number	7440-52-0
Selected isotopes
Main article: Isotopes of erbium iso NA half-life DM DE ( MeV) DP 160Er syn 28.58 h ε 0.330 160Ho 162Er 0.139% 162Er is stable with 94 neutrons 164Er 1.601% 164Er is stable with 96 neutrons 165Er syn 10.36 h ε 0.376 165Ho 166Er 33.503% 166Er is stable with 98 neutrons 167Er 22.869% 167Er is stable with 99 neutrons 168Er 26.978% 168Er is stable with 100 neutrons 169Er syn 9.4 d β- 0.351 169Tm 170Er 14.910% 170Er is stable with 102 neutrons 171Er syn 7.516 h β- 1.490 171Tm 172Er syn 49.3 h β- 0.891 172Tm
References

Erbium (pronounced /ˈɝbiəm/) is a chemical element with the symbol Er and atomic number 68. A rare, silvery, white metallic lanthanide; Erbium is a solid in its normal state. It is a rare earth element, erbium is associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden.

Notable characteristics

A trivalent element, pure erbium metal is malleable (or easily shaped), soft yet stable in air, and does not oxidize as quickly as some other rare-earth metals. Its salts are rose-colored, and the element has characteristic sharp absorption spectra bands in visible light, ultraviolet, and near infrared. Otherwise it looks much like the other rare earths. Its sesquioxide is called erbia. Erbium's properties are to a degree dictated by the kind and amount of impurities present. Erbium does not play any known biological role, but is thought by some to be able to stimulate metabolism. Erbium-doped glasses or crystals can be used as optical amplification media, where erbium ions are optically pumped at around 980nm or 1480nm and then radiate light at 1550nm. This process can be used to create lasers and optical amplifiers. The 1550nm wavelength is especially important for optical communications because standard single mode optical fibers have minimal loss at this particular wavelength. A large variety of medical applications can be found (i.e. dermatology, dentistry) by utilizing the 2940nm emission (see Er:YAG_laser) which is highly absorped in water (about 12000 1/cm).

Applications

Erbium's everyday uses are varied. It is commonly used as a photographic filter, and because of its resilience it is useful as a metallurgical additive. Other uses:

• Used in nuclear technology as a neutron absorber (moderator).
• Used as a dopant in fibre-optic laser amplifiers.
• When added to vanadium as an alloy, erbium lowers hardness and improves workability.
• Erbium oxide has a pink colour, and is sometimes used as a colorant for glass and porcelain. The glass is then often used in sunglasses and cheap jewelry.
• Erbium is also used to provide the pink color in cubic zirconia, also used in inexpensive jewelry. The pink colour is especially intense and beautiful under white fluorescent lighting.
• Erbium-doped optical silica-glass fibers are the active element in erbium-doped fibre amplifiers (EDFAs), which are widely used in optical communications. The same fibers can be used to create fibre lasers. Co-doping of optical fibre with Er and Yb is used in high-power Er/Yb fibre lasers, which gradually replace CO₂ lasers for metal welding and cutting applications. Erbium can also be used in erbium-doped waveguide amplifiers.

History

Erbium (for Ytterby, a town in Sweden) was discovered by Carl Gustaf Mosander in 1843. Mosander separated "yttria" from the mineral gadolinite into three fractions which he called yttria, erbia, and terbia. He named the new element after the town of Ytterby where large concentrations of yttria and erbium are located. Erbia and terbia, however, were confused at this time. After 1860, terbia was renamed erbia and after 1877 what had been known as erbia was renamed terbia. Fairly pure Er₂O₃ was independently isolated in 1905 by Georges Urbain and Charles James. Reasonably pure metal wasn't produced until 1934 when workers reduced the anhydrous chloride with potassium vapor.

Occurrence

Like other rare earths, this element is never found as a free element in nature but is found bound in monazite sand ores. It has historically been very difficult and expensive to separate rare earths from each other in their ores but ion-exchange production techniques developed in the late 20th century have greatly brought down the cost of production of all rare-earth metals and their chemical compounds. The principal commercial sources of erbium are from the minerals xenotime and euxenite, and most recently, the ion adsorption clays of southern China. In the high-yttrium versions of these ore concentrates, yttrium is about two-thirds of the total by weight, and erbia is about 4-5%. This is enough erbium to impart a distinct pink color to the solution when the concentrate is dissolved in acid. This color behaviour is highly similar to what Mosander and the other early workers in the lanthanides would have seen, in their extracts from Ytterby gadolinite.

Isotopes

Naturally occurring erbium is composed of 6 stable isotopes, Er-162, Er-164, Er-166, Er-167, Er-168, and Er-170 with Er-166 being the most abundant (33.503% natural abundance). 29 radioisotopes have been characterized, with the most stable being Er-169 with a half life of 9.4 days, Er-172 with a half-life of 49.3 hours, Er-160 with a half-life of 28.58 hours, Er-165 with a half-life of 10.36 hours, and Er-171 with a half life of 7.516 hours. All of the remaining radioactive isotopes have half-lifes that are less than 3.5 hours, and the majority of these have half lifes that are less than 4 minutes. This element also has 13 meta states, with the most stable being Er-167m (t_½ 2.269 seconds).

The isotopes of erbium range in atomic weight from 142.9663 u (Er-143) to 176.9541 u (Er-177). The primary decay mode before the most abundant stable isotope, Er-166, is electron capture, and the primary mode after is beta decay. The primary decay products before Er-166 are element 67 (holmium) isotopes, and the primary products after are element 69 (thulium) isotopes.

Precautions

As with the other lanthanides, erbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Metallic erbium in dust form presents a fire and explosion hazard.