Erbium

\( \require{mhchem} \)

Erbium is a chemical element; it has symbol Er and atomic number 68. A silvery-white[5] solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements. It is a lanthanide, a rare-earth element, originally found in the gadolinite mine in Ytterby, Sweden, which is the source of the element's name.

Erbium, ₆₈Er

Erbium

Pronunciation

/ˈɜːrbiəm/ (UR-bee-əm)

Appearance

silvery white

Standard atomic weight A_r°(Er)

167.259±0.003
167.26±0.01 (abridged)^[1]

Erbium in the periodic table

Atomic number (Z)

Group

f-block groups (no number)

Period

period 6

Block

f-block

Electron configuration

[Xe] 4f¹² 6s²

Electrons per shell

2, 8, 18, 30, 8, 2

Physical properties

Phase at STP

solid

Melting point

1802 K (1529 °C, 2784 °F)

Boiling point

3141 K (2868 °C, 5194 °F)

Density (near r.t.)

9.066 g/cm³

when liquid (at m.p.)

8.86 g/cm³

Heat of fusion

19.90 kJ/mol

Heat of vaporization

280 kJ/mol

Molar heat capacity

28.12 J/(mol·K)

Vapor pressure

P (Pa)	1	10	100	1 k	10 k	100 k
at T (K)	1504	1663	(1885)	(2163)	(2552)	(3132)

Atomic properties

Oxidation states

0,^[2] +1, +2, +3 (a basic oxide)

Electronegativity

Pauling scale: 1.24

Ionization energies

1st: 589.3 kJ/mol
2nd: 1150 kJ/mol
3rd: 2194 kJ/mol

Atomic radius

empirical: 176 pm

Covalent radius

189±6 pm

Spectral lines of erbium

Other properties

Natural occurrence

primordial

Crystal structure

hexagonal close-packed (hcp)

Speed of sound thin rod

2830 m/s (at 20 °C)

Thermal expansion

poly: 12.2 µm/(m⋅K) (r.t.)

Thermal conductivity

14.5 W/(m⋅K)

Electrical resistivity

poly: 0.860 µΩ⋅m (r.t.)

Magnetic ordering

paramagnetic at 300 K

Molar magnetic susceptibility

+44300.00×10⁻⁶ cm³/mol^[3]

Young's modulus

69.9 GPa

Shear modulus

28.3 GPa

Bulk modulus

44.4 GPa

Poisson ratio

0.237

Vickers hardness

430–700 MPa

Brinell hardness

600–1070 MPa

CAS Number

7440-52-0

History

Naming

after Ytterby (Sweden), where it was mined

Discovery

Carl Gustaf Mosander (1843)

Isotopes of erbium

Main isotopes^[4]			Decay
	abundance	half-life (t_1/2)	mode	product
¹⁶⁰Er	synth	28.58 h	ε	¹⁶⁰Ho
¹⁶²Er	0.139%	stable
¹⁶⁴Er	1.60%	stable
¹⁶⁵Er	synth	10.36 h	ε	¹⁶⁵Ho
¹⁶⁶Er	33.5%	stable
¹⁶⁷Er	22.9%	stable
¹⁶⁸Er	27.0%	stable
¹⁶⁹Er	synth	9.4 d	β⁻	¹⁶⁹Tm
¹⁷⁰Er	14.9%	stable
¹⁷¹Er	synth	7.516 h	β⁻	¹⁷¹Tm
¹⁷²Er	synth	49.3 h	β⁻	¹⁷²Tm

Erbium's principal uses involve its pink-colored Er3+ ions, which have optical fluorescent properties particularly useful in certain laser applications. Erbium-doped glasses or crystals can be used as optical amplification media, where Er3+ ions are optically pumped at around 980 or 1480 nm and then radiate light at 1530 nm in stimulated emission. This process results in an unusually mechanically simple laser optical amplifier for signals transmitted by fiber optics. The 1550 nm wavelength is especially important for optical communications because standard single mode optical fibers have minimal loss at this particular wavelength.

In addition to optical fiber amplifier-lasers, a large variety of medical applications (i.e. dermatology, dentistry) rely on the erbium ion's 2940 nm emission (see Er:YAG laser) when lit at another wavelength, which is highly absorbed in water in tissues, making its effect very superficial. Such shallow tissue deposition of laser energy is helpful in laser surgery, and for the efficient production of steam which produces enamel ablation by common types of dental laser.

Characteristics
Physical properties
Erbium(III) chloride in sunlight, showing some pink fluorescence of Er+3 from natural ultraviolet.

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.[6] 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 to be able to stimulate metabolism.[7]

Erbium is ferromagnetic below 19 K, antiferromagnetic between 19 and 80 K and paramagnetic above 80 K.[8]

Erbium can form propeller-shaped atomic clusters Er3N, where the distance between the erbium atoms is 0.35 nm. Those clusters can be isolated by encapsulating them into fullerene molecules, as confirmed by transmission electron microscopy.[9]

Like most rare-earth elements, erbium is usually found in the +3 oxidation state. However, it is possible for erbium to also be found in the 0, +1 and +2 oxidation states.
Chemical properties

Erbium metal retains its luster in dry air, however will tarnish slowly in moist air and burns readily to form erbium(III) oxide:[10]

\( \ce{4Er + 3O2 -> 2Er2O3} \)

Erbium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form erbium hydroxide:[11]

\( \ce{ 2Er (s) + 6H2O (l) -> 2Er(OH)3 (aq) + 3H2 (g) } \)

Erbium metal reacts with all the halogens:[12]

\( \ce{ 2Er (s) + 3F2 (g) -> 2ErF3 (s) } \) [pink]
\( \ce{2Er (s) + 3Cl2 (g) -> 2ErCl3 (s) } \) [violet]
\( \ce{2Er (s) + 3Br2 (g) -> 2ErBr3 (s) } \) [violet]
\( \ce{2Er (s) + 3I2 (g) -> 2ErI3 (s) } \) [violet]

Erbium dissolves readily in dilute sulfuric acid to form solutions containing hydrated Er(III) ions, which exist as rose red \( \ce{[Er(OH2)9]3+} \) hydration complexes:[12]

\( \ce{2Er (s) + 3H2SO4 (aq) → 2Er3+ (aq) + 3SO2−} \)
\( \ce{4(aq) + 3H2 (g)} \)

Isotopes
Main article: Isotopes of erbium

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

The isotopes of erbium range in atomic weight from 142.9663 u (¹⁴³Er ) to 176.9541 u (¹⁷⁷Er ). The primary decay mode before the most abundant stable isotope, ¹⁶⁶Er, is electron capture, and the primary mode after is beta decay. The primary decay products before ¹⁶⁶Er are element 67 (holmium) isotopes, and the primary products after are element 69 (thulium) isotopes.^[13]

Compounds
Main article: Erbium compounds
Oxides
Erbium(III) oxide powder
Main article: Erbium(III) oxide

Erbium(III) oxide (also known as erbia) is the only known oxide of erbium, first isolated by Carl Gustaf Mosander in 1843, and first obtained in pure form in 1905 by Georges Urbain and Charles James.[14] It has a cubic structure resembling the bixbyite motif. The Er3+ centers are octahedral.[15] The formation of erbium oxide is accomplished by burning erbium metal.[16] Erbium oxide is insoluble in water and soluble in mineral acids.
Halides
Erbium(III) chloride hydrate

Erbium(III) fluoride is a pinkish powder[17] that can be produced by reacting erbium(III) nitrate and ammonium fluoride.[18] It can be used to make infrared light-transmitting materials[19] and up-converting luminescent materials.[20] Erbium(III) chloride is a violet compounds that can be formed by first heating erbium(III) oxide and ammonium chloride to produce the ammonium salt of the pentachloride ([NH4]2ErCl5) then heating it in a vacuum at 350-400 °C.[21][22][23] It forms crystals of the AlCl3 type, with monoclinic crystals and the point group C2/m.[24] Erbium(III) chloride hexahydrate also forms monoclinic crystals with the point group of P2/n (P2/c) - C42h. In this compound, erbium is octa-coordinated to form [Er(H2O)6Cl2]+ ions with the isolated Cl− completing the structure.[25]

Erbium(III) bromide is a violet solid. It is used, like other metal bromide compounds, in water treatment, chemical analysis and for certain crystal growth applications.[26] Erbium(III) iodide[27] is a slightly pink compound that is insoluble in water. It can be prepared by directly reacting erbium with iodine.[28]
Organoerbium compounds
See also: Organolanthanide chemistry

Organoerbium compounds are very similar to those of the other lanthanides, as they all share an inability to undergo π backbonding. They are thus mostly restricted to the mostly ionic cyclopentadienides (isostructural with those of lanthanum) and the σ-bonded simple alkyls and aryls, some of which may be polymeric.[29]
History
Carl Gustaf Mosander, the scientist who discovered erbium, lanthanum and terbium.

Erbium (for Ytterby, a village in Sweden) was discovered by Carl Gustaf Mosander in 1843.[30] Mosander was working with a sample of what was thought to be the single metal oxide yttria, derived from the mineral gadolinite. He discovered that the sample contained at least two metal oxides in addition to pure yttria, which he named "erbia" and "terbia" after the village of Ytterby where the gadolinite had been found. Mosander was not certain of the purity of the oxides and later tests confirmed his uncertainty. Not only did the "yttria" contain yttrium, erbium, and terbium; in the ensuing years, chemists, geologists and spectroscopists discovered five additional elements: ytterbium, scandium, thulium, holmium, and gadolinium.[31]: 701 [32][33][34][35][36]

Erbia and terbia, however, were confused at this time. A spectroscopist mistakenly switched the names of the two elements during spectroscopy. 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 erbium metal was not produced until 1934 when Wilhelm Klemm and Heinrich Bommer reduced the anhydrous chloride with potassium vapor.[37] It was only in the 1990s that the price for Chinese-derived erbium oxide became low enough for erbium to be considered for use as a colorant in art glass.[38]
Occurrence
Monazite sand

The concentration of erbium in the Earth crust is about 2.8 mg/kg and in seawater 0.9 ng/L.[39] Erbium is the 44th most abundant element in the Earth's crust at about 3.0–3.8 ppm.

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 chromatography methods[40] 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 consequence, China has now become the principal global supplier of this element.[41] 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%. When the concentrate is dissolved in acid, the erbia liberates enough erbium ion to impart a distinct and characteristic pink color to the solution. This color behavior is similar to what Mosander and the other early workers in the lanthanides would have seen in their extracts from the gadolinite minerals of Ytterby.
Production

Crushed minerals are attacked by hydrochloric or sulfuric acid that transforms insoluble rare-earth oxides into soluble chlorides or sulfates. The acidic filtrates are partially neutralized with caustic soda (sodium hydroxide) to pH 3–4. Thorium precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3. The solution is treated with magnesium nitrate to produce a crystallized mixture of double salts of rare-earth metals. The salts are separated by ion exchange. In this process, rare-earth ions are sorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by suitable complexing agent.[39] Erbium metal is obtained from its oxide or salts by heating with calcium at 1450 °C under argon atmosphere.[39]
Applications
Erbium-colored glass

Erbium's everyday uses are varied. It is commonly used as a photographic filter,[42] and because of its resilience it is useful as a metallurgical additive.
Lasers and optics

A large variety of medical applications (i.e. dermatology, dentistry) utilize erbium ion's 2940 nm emission (see Er:YAG laser), which is highly absorbed in water (absorption coefficient about 12000/cm). Such shallow tissue deposition of laser energy is necessary for laser surgery, and the efficient production of steam for laser enamel ablation in dentistry.[43]

Erbium-doped optical silica-glass fibers are the active element in erbium-doped fiber amplifiers (EDFAs), which are widely used in optical communications.[44] The same fibers can be used to create fiber lasers. In order to work efficiently, erbium-doped fiber is usually co-doped with glass modifiers/homogenizers, often aluminium or phosphorus. These dopants help prevent clustering of Er ions and transfer the energy more efficiently between excitation light (also known as optical pump) and the signal. Co-doping of optical fiber with Er and Yb is used in high-power Er/Yb fiber lasers. Erbium can also be used in erbium-doped waveguide amplifiers.[7]
Other applications

When added to vanadium as an alloy, erbium lowers hardness and improves workability.[45] An erbium-nickel alloy Er3Ni has an unusually high specific heat capacity at liquid-helium temperatures and is used in cryocoolers; a mixture of 65% Er3Co and 35% Er0.9Yb0.1Ni by volume improves the specific heat capacity even more.[46][47]

Erbium oxide has a pink color, and is sometimes used as a colorant for glass, cubic zirconia and porcelain. The glass is then often used in sunglasses and cheap jewelry.[45][48]

Erbium is used in nuclear technology in neutron-absorbing control rods.[7][49] or as a burnable poison in nuclear fuel design.[50] Recently, erbium has been used in experiments related to lattice confinement fusion.[51][52]
Biological role and precautions

Erbium does not have a biological role, but erbium salts can stimulate metabolism. Humans consume 1 milligram of erbium a year on average. The highest concentration of erbium in humans is in the bones, but there is also erbium in the human kidneys and liver.[7] Erbium is slightly toxic if ingested, but erbium compounds are not toxic.[7] Metallic erbium in dust form presents a fire and explosion hazard.[53][54][55]
References

"Standard Atomic Weights: Erbium". CIAAW. 1999.
Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
"Erbium (Er) | AMERICAN ELEMENTS ®". American Elements: The Materials Science Company. Retrieved 2023-10-31.
Humpidge, J. S.; Burney, W. (1879-01-01). "XIV.—On erbium and yttrium". Journal of the Chemical Society, Transactions. 35: 111–117. doi:10.1039/CT8793500111. ISSN 0368-1645.
Emsley, John (2001). "Erbium". Nature's Building Blocks: An A-Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 136–139. ISBN 978-0-19-850340-8.
Jackson, M. (2000). "Magnetism of Rare Earth" (PDF). The IRM Quarterly. 10 (3): 1. Archived from the original (PDF) on 2017-07-12. Retrieved 2009-05-03.
Sato, Yuta; Suenaga, Kazu; Okubo, Shingo; Okazaki, Toshiya; Iijima, Sumio (2007). "Structures of D5d-C80 and Ih-Er3N@C80 Fullerenes and Their Rotation Inside Carbon Nanotubes Demonstrated by Aberration-Corrected Electron Microscopy". Nano Letters. 7 (12): 3704. Bibcode:2007NanoL...7.3704S. doi:10.1021/nl0720152.
Emsley, John (2001). "Erbium" Nature's Building Blocks: An A-Z Guide to Elements. Oxford, England, Uk: Oxford University Press. pp. 136–139. ISBN 978-0-19-850340-8.
Assaaoudi, H.; Fang, Z.; Butler, I. S.; Kozinski, J. A. (2008). "Synthesis of erbium hydroxide microflowers and nanostructures in subcritical water". Nanotechnology. 19 (18): 185606. Bibcode:2008Nanot..19r5606A. doi:10.1088/0957-4484/19/18/185606. PMID 21825694. S2CID 24755693.
"Chemical reactions of Erbium". Webelements. Retrieved 2009-06-06.
Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A. 729 (1): 3–128. Bibcode:2003NuPhA.729....3A. CiteSeerX 10.1.1.692.8504. doi:10.1016/j.nuclphysa.2003.11.001.
Aaron John Ihde (1984). The development of modern chemistry. Courier Dover Publications. pp. 378–379. ISBN 978-0-486-64235-2.
Adachi, Gin-ya; Imanaka, Nobuhito (1998). "The Binary Rare Earth Oxides". Chemical Reviews. 98 (4): 1479–1514. doi:10.1021/cr940055h. PMID 11848940.
Emsley, John (2001). "Erbium" Nature's Building Blocks: An A-Z Guide to Elements. Oxford, England, Uk: Oxford University Press. pp. 136–139. ISBN 978-0-19-850340-8.
"Erbium Fluoride".
Linna Guo, Yuhua Wang, Zehua Zou, Bing Wang, Xiaoxia Guo, Lili Han, Wei Zeng (2014). "Facile synthesis and enhancement upconversion luminescence of ErF3 nano/microstructures via Li+ doping". Journal of Materials Chemistry C. 2 (15): 2765. doi:10.1039/c3tc32540g. ISSN 2050-7526. Retrieved 2019-03-26.
苏伟涛, 李斌, 刘定权,等. 氟化铒薄膜晶体结构与红外光学性能的关系[J]. 物理学报, 2007, 56(5):2541-2546.
Yingxin Hao, Shichao Lv, Zhijun Ma, Jianrong Qiu (2018). "Understanding differences in Er 3+ –Yb 3+ codoped glass and glass ceramic based on upconversion luminescence for optical thermometry". RSC Advances. 8 (22): 12165–12172. doi:10.1039/C8RA01245H. ISSN 2046-2069. PMC 9079277. PMID 35539388.
Brauer, G., ed. (1963). Handbook of Preparative Inorganic Chemistry (2nd ed.). New York: Academic Press.
Meyer, G. (1989). "The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides—The Example of Ycl 3". The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides-The Example of YCl3. Inorganic Syntheses. Vol. 25. pp. 146–150. doi:10.1002/9780470132562.ch35. ISBN 978-0-470-13256-2.
Edelmann, F. T.; Poremba, P. (1997). Herrmann, W. A. (ed.). Synthetic Methods of Organometallic and Inorganic Chemistry. Vol. VI. Stuttgart: Georg Thieme Verlag. ISBN 978-3-13-103021-4.
Tempelton DH, Carter GF (1954). "The Crystal Structure of Yttrium Trichloride and Similar Compounds". J Phys Chem. 58 (11): 940–943. doi:10.1021/j150521a002.
Graebner EJ, Conrad GH, Duliere SF (1966). "Crystallographic data for solvated rare earth chlorides". Acta Crystallographica. 21 (6): 1012–1013. doi:10.1107/S0365110X66004420.
Elements, American. "Erbium Bromide". American Elements. Retrieved 2020-11-16.
Perry, Dale L (2011). Handbook of Inorganic Compounds (2 ed.). Taylor & Francis. p. 163. ISBN 9781439814628. Retrieved 14 December 2013.
Elements, American. "Erbium Iodide". American Elements. Retrieved 2020-11-16.
Greenwood and Earnshaw, pp. 1248–9
Mosander, C. G. (1843). "On the new metals, Lanthanium and Didymium, which are associated with Cerium; and on Erbium and Terbium, new metals associated with Yttria". Philosophical Magazine. 23 (152): 241–254. doi:10.1080/14786444308644728. Note: The first part of this article, which does NOT concern erbium, is a translation of: C. G. Mosander (1842) "Något om Cer och Lanthan" [Some (news) about cerium and lanthanum], Förhandlingar vid de Skandinaviske naturforskarnes tredje möte (Stockholm) [Transactions of the Third Scandinavian Scientist Conference (Stockholm)], vol. 3, pp. 387–398.
Weeks, Mary Elvira (1956). The discovery of the elements (6th ed.). Easton, PA: Journal of Chemical Education.
Weeks, Mary Elvira (1932). "The discovery of the elements: XVI. The rare earth elements". Journal of Chemical Education. 9 (10): 1751–1773. Bibcode:1932JChEd...9.1751W. doi:10.1021/ed009p1751.
Marshall, James L. Marshall; Marshall, Virginia R. Marshall (2015). "Rediscovery of the elements: The Rare Earths–The Beginnings" (PDF). The Hexagon: 41–45. Retrieved 30 December 2019.
Marshall, James L. Marshall; Marshall, Virginia R. Marshall (2015). "Rediscovery of the elements: The Rare Earths–The Confusing Years" (PDF). The Hexagon: 72–77. Retrieved 30 December 2019.
Piguet, Claude (2014). "Extricating erbium". Nature Chemistry. 6 (4): 370. Bibcode:2014NatCh...6..370P. doi:10.1038/nchem.1908. PMID 24651207.
"Erbium". Royal Society of Chemistry. 2020. Retrieved 4 January 2020.
"Facts About Erbium". Live Science. July 23, 2013. Retrieved 22 October 2018.
Ihde, Aaron John (1984). The development of modern chemistry. Courier Dover Publications. pp. 378–379. ISBN 978-0-486-64235-2.
Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 293–295. ISBN 978-0-07-049439-8. Retrieved 2009-06-06.
Early paper on the use of displacement ion-exchange chromatography to separate rare earths: Spedding, F. H.; Powell, J. E. (1954). "A practical separation of yttrium group rare earths from gadolinite by ion-exchange". Chemical Engineering Progress. 50: 7–15.
Asad, F. M. M. (2010). Optical Properties of Dye Sensitized Zinc Oxide Thin Film Deposited by Sol-gel Method (Doctoral dissertation, Universiti Teknologi Malaysia).
Awwad, N. S.; Gad, H. M. H.; Ahmad, M. I.; Aly, H. F. (2010-12-01). "Sorption of lanthanum and erbium from aqueous solution by activated carbon prepared from rice husk". Colloids and Surfaces B: Biointerfaces. 81 (2): 593–599. doi:10.1016/j.colsurfb.2010.08.002. ISSN 0927-7765. PMID 20800456.
Šulc, J.; Jelínková, H. (2013-01-01), Jelínková, Helena (ed.), "5 - Solid-state lasers for medical applications", Lasers for Medical Applications, Woodhead Publishing Series in Electronic and Optical Materials, Woodhead Publishing, pp. 127–176, doi:10.1533/9780857097545.2.127, ISBN 978-0-85709-237-3, retrieved 2022-04-28
Becker, P. C.; Olsson, N. A.; Simpson, J. R. (1999). Erbium-doped fiber amplifiers fundamentals and technology. San Diego: Academic Press. ISBN 978-0-12-084590-3.
Hammond, C. R. (2000). The Elements, in Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0481-1.
Kittel, Peter (ed.). Advances in Cryogenic Engineering. Vol. 39a.
Ackermann, Robert A. (1997). Cryogenic Regenerative Heat Exchangers. Springer. p. 58. ISBN 978-0-306-45449-3.
Stwertka, Albert. A Guide to the Elements, Oxford University Press, 1996, p. 162. ISBN 0-19-508083-1
Parish, Theodore A.; Khromov, Vyacheslav V.; Carron, Igor, eds. (1999). "Use of UraniumErbium and PlutoniumErbium Fuel in RBMK Reactors". Safety issues associated with Plutonium involvement in the nuclear fuel cycle. CBoston: Kluwer. pp. 121–125. ISBN 978-0-7923-5593-9.
Grossbeck, Renier, and Bigelow (September 2003). "DEVELOPMENT OF IMPROVED BURNABLE POISONS FOR COMMERCIAL NUCLEAR POWER REACTORS" (PDF). University of North Texas (UNT) digital library.
"NASA's New Shortcut to Fusion Power". 27 February 2022.
Steinetz, Bruce M.; Benyo, Theresa L.; Chait, Arnon; Hendricks, Robert C.; Forsley, Lawrence P.; Baramsai, Bayarbadrakh; Ugorowski, Philip B.; Becks, Michael D.; Pines, Vladimir; Pines, Marianna; Martin, Richard E.; Penney, Nicholas; Fralick, Gustave C.; Sandifer, Carl E. (2020). "Novel nuclear reactions observed in bremsstrahlung-irradiated deuterated metals". Physical Review C. 101 (4): 044610. Bibcode:2020PhRvC.101d4610S. doi:10.1103/PhysRevC.101.044610. S2CID 219083603.
Haley, T. J.; Koste, L.; Komesu, N.; Efros, M.; Upham, H. C. (1966). "Pharmacology and toxicology of dysprosium, holmium, and erbium chlorides". Toxicology and Applied Pharmacology. 8 (1): 37–43. doi:10.1016/0041-008x(66)90098-6. PMID 5921895.
Haley, T. J. (1965). "Pharmacology and toxicology of the rare earth elements". Journal of Pharmaceutical Sciences. 54 (5): 663–70. doi:10.1002/jps.2600540502. PMID 5321124.

Bruce, D. W.; Hietbrink, B. E.; Dubois, K. P. (1963). "The acute mammalian toxicity of rare earth nitrates and oxides". Toxicology and Applied Pharmacology. 5 (6): 750–9. doi:10.1016/0041-008X(63)90067-X. PMID 14082480.