Terbium is a chemical element with symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, ductile, and soft enough to be cut with a knife. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with water, evolving hydrogen gas. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime, and euxenite.

Swedish chemist Carl Gustaf Mosander discovered terbium as a chemical element in 1843. He detected it as an impurity in yttrium oxide, Y2O3. Yttrium and terbium are named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques.

Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures. As a component of Terfenol-D (an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuators, in naval sonar systems and in sensors.

Most of the world's terbium supply is used in green phosphors. Terbium oxide is in fluorescent lamps and television and monitor cathode ray tubes (CRTs). Terbium green phosphors are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide trichromatic lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.

Terbium,  65Tb
Pronunciation/ˈtɜːrbiəm/ (TUR-bee-əm)
Appearancesilvery white
Standard atomic weight Ar, std(Tb)158.925354(8)[1]
Terbium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


Atomic number (Z)65
Groupgroup n/a
Periodperiod 6
Element category  lanthanide
Electron configuration[Xe] 4f9 6s2
Electrons per shell
2, 8, 18, 27, 8, 2
Physical properties
Phase at STPsolid
Melting point1629 K ​(1356 °C, ​2473 °F)
Boiling point3396 K ​(3123 °C, ​5653 °F)
Density (near r.t.)8.23 g/cm3
when liquid (at m.p.)7.65 g/cm3
Heat of fusion10.15 kJ/mol
Heat of vaporization391 kJ/mol
Molar heat capacity28.91 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1789 1979 (2201) (2505) (2913) (3491)
Atomic properties
Oxidation states+1, +2, +3, +4 (a weakly basic oxide)
ElectronegativityPauling scale: 1.2 (?)
Ionization energies
  • 1st: 565.8 kJ/mol
  • 2nd: 1110 kJ/mol
  • 3rd: 2114 kJ/mol
Atomic radiusempirical: 177 pm
Covalent radius194±5 pm
Color lines in a spectral range
Spectral lines of terbium
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for terbium
Speed of sound thin rod2620 m/s (at 20 °C)
Thermal expansionat r.t. α, poly: 10.3 µm/(m·K)
Thermal conductivity11.1 W/(m·K)
Electrical resistivityα, poly: 1.150 µΩ·m (at r.t.)
Magnetic orderingparamagnetic at 300 K
Magnetic susceptibility+146,000·10−6 cm3/mol (273 K)[2]
Young's modulusα form: 55.7 GPa
Shear modulusα form: 22.1 GPa
Bulk modulusα form: 38.7 GPa
Poisson ratioα form: 0.261
Vickers hardness450–865 MPa
Brinell hardness675–1200 MPa
CAS Number7440-27-9
Namingafter Ytterby (Sweden), where it was mined
Discovery and first isolationCarl Gustaf Mosander (1843)
Main isotopes of terbium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
157Tb syn 71 y ε 157Gd
158Tb syn 180 y ε 158Gd
β 158Dy
159Tb 100% stable


Physical properties

Terbium is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife.[3] It is relatively stable in air compared to the earlier, more reactive lanthanides in the first half of the lanthanide series.[4] Terbium exists in two crystal allotropes with a transformation temperature of 1289 °C between them.[3] The 65 electrons of a terbium atom are arranged in the electron configuration [Xe]4f96s2; normally, only three electrons can be removed before the nuclear charge becomes too great to allow further ionization, but in the case of terbium, the stability of the half-filled [Xe]4f7 configuration allows further ionization of a fourth electron in the presence of very strong oxidizing agents such as fluorine gas.[3]

The terbium(III) cation is brilliantly fluorescent, in a bright lemon-yellow color that is the result of a strong green emission line in combination with other lines in the orange and red. The yttrofluorite variety of the mineral fluorite owes its creamy-yellow fluorescence in part to terbium. Terbium easily oxidizes, and is therefore used in its elemental form specifically for research. Single terbium atoms have been isolated by implanting them into fullerene molecules.[5]

Terbium has a simple ferromagnetic ordering at temperatures below 219 K. Above 219 K, it turns into a helical antiferromagnetic state in which all of the atomic moments in a particular basal plane layer are parallel, and oriented at a fixed angle to the moments of adjacent layers. This unusual antiferromagnetism transforms into a disordered paramagnetic state at 230 K.[6]

Chemical properties

The most common oxidation state of terbium is +3, as in Tb
. The +4 state is known in TbO2 and TbF4.[7][8] Terbium burns readily to form a mixed terbium(III,IV) oxide:[9]

8 Tb + 7 O2 → 2 Tb4O7

In solution, terbium forms only trivalent ions. Terbium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form terbium hydroxide:[9]

2 Tb + 6 H2O → 2 Tb(OH)3 + 3 H2

Terbium metal reacts with all the halogens, forming white trihalides:[9]

2 Tb + 3 X2 → 2 TbX3 (X = F, Cl, Br, I)

Terbium dissolves readily in dilute sulfuric acid to form solutions containing the pale pink terbium(III) ions, which exist as [Tb(OH2)9]3+ complexes:[9]

2 Tb (s) + 3 H2SO4 → 2 Tb3+ + 3 SO2−
+ 3 H2


Terbium sulfate, Tb2(SO4)3 (top), fluoresces green under ultraviolet light (bottom)

Terbium combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic at elevated temperatures, forming various binary compounds such as TbH2, TbH3, TbB2, Tb2S3, TbSe, TbTe and TbN.[8] In those compounds, Tb mostly exhibits the oxidation states +3 and sometimes +2. Terbium(II) halogenides are obtained by annealing Tb(III) halogenides in presence of metallic Tb in tantalum containers. Terbium also forms sesquichloride Tb2Cl3, which can be further reduced to TbCl by annealing at 800 °C. This terbium(I) chloride forms platelets with layered graphite-like structure.[10]

Other compounds include

Terbium(IV) fluoride is a strong fluorinating agent, emitting relatively pure atomic fluorine when heated[11] rather than the mixture of fluoride vapors emitted from CoF3 or CeF4.


Naturally occurring terbium is composed of its only stable isotope, terbium-159; the element is thus called mononuclidic and monoisotopic. Thirty-six radioisotopes have been characterized, with the heaviest being terbium-171 (with atomic mass of 170.95330(86) u) and lightest being terbium-135 (exact mass unknown).[12] The most stable synthetic radioisotopes of terbium are terbium-158, with a half-life of 180 years, and terbium-157, with a half-life of 71 years. All of the remaining radioactive isotopes have half-lives that are much less than a quarter of a year, and the majority of these have half-lives that are less than half a minute.[12] The primary decay mode before the most abundant stable isotope, 159Tb, is electron capture, which results in production of gadolinium isotopes, and the primary mode after is beta minus decay, resulting in dysprosium isotopes.[12]

The element also has 27 nuclear isomers, with masses of 141–154, 156, and 158 (not every mass number corresponds to only one isomer). The most stable of them are terbium-156m, with half-life of 24.4 hours and terbium-156m2, with half-life of 22.7 hours; this is longer than half-lives of most ground states of radioactive terbium isotopes, except only those with mass numbers 155–161.[12]


Swedish chemist Carl Gustaf Mosander discovered terbium in 1843. He detected it as an impurity in yttrium oxide, Y2O3. Yttrium is named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques.[13]

Mosander first separated yttria into three fractions, all named for the ore: yttria, erbia, and terbia. "Terbia" was originally the fraction that contained the pink color, due to the element now known as erbium. "Erbia" (containing what we now call terbium) originally was the fraction that was essentially colorless in solution. The insoluble oxide of this element was noted to be tinged brown.

Later workers had difficulty in observing the minor colorless "erbia", but the soluble pink fraction was impossible to miss. Arguments went back and forth as to whether erbia even existed. In the confusion, the original names got reversed, and the exchange of names stuck, so that the pink fraction referred eventually to the solution containing erbium (which in solution, is pink). It is now thought that workers using double sodium or potassium sulfates to remove ceria from yttria inadvertently lost the terbium into the ceria-containing precipitate. What is now known as terbium was only about 1% of the original yttria, but that was sufficient to impart a yellowish color to the yttrium oxide. Thus, terbium was a minor component in the original fraction containing it, where it was dominated by its immediate neighbors, gadolinium and dysprosium.

Thereafter, whenever other rare earths were teased apart from this mixture, whichever fraction gave the brown oxide retained the terbium name, until at last, the brown oxide of terbium was obtained in pure form. The 19th century investigators did not have the benefit of the UV fluorescence technology to observe the brilliant yellow or green Tb(III) fluorescence that would have made terbium easier to identify in solid mixtures or solutions.[13]


Xenotim mineralogisches museum bonn

Terbium is contained along with other rare earth elements in many minerals, including monazite ((Ce,La,Th,Nd,Y)PO4 with up to 0.03% terbium), xenotime (YPO4) and euxenite ((Y,Ca,Er,La,Ce,U,Th)(Nb,Ta,Ti)2O6 with 1% or more terbium). The crust abundance of terbium is estimated as 1.2 mg/kg.[8] No terbium-dominant mineral has yet been found.[14]

Currently, the richest commercial sources of terbium are the ion-adsorption clays of southern China; the concentrates with about two-thirds yttrium oxide by weight have about 1% terbia. Small amounts of terbium occur in bastnäsite and monazite; when these are processed by solvent extraction to recover the valuable heavy lanthanides as samarium-europium-gadolinium concentrate, terbium is recovered therein. Due to the large volumes of bastnäsite processed relative to the ion-adsorption clays, a significant proportion of the world's terbium supply comes from bastnäsite.[3]

In 2018, a rich terbium supply was discovered off the coast of Japan's Minamitori Island, with the stated supply being "enough to meet the global demand for 420 years".[15]


Crushed terbium-containing minerals are treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with caustic soda 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 decomposed to oxides by heating. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3. Terbium is separated as a double salt with ammonium nitrate by crystallization.[8]

The most efficient separation routine for terbium salt from the rare-earth salt solution is 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. As with other rare earths, terbium metal is produced by reducing the anhydrous chloride or fluoride with calcium metal. Calcium and tantalum impurities can be removed by vacuum remelting, distillation, amalgam formation or zone melting.[8]


Terbium is used as a dopant in calcium fluoride, calcium tungstate, and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures, together with ZrO2.[3]

Terbium is also used in alloys and in the production of electronic devices. As a component of Terfenol-D, terbium is used in actuators, in naval sonar systems, sensors, in the SoundBug device (its first commercial application), and other magnetomechanical devices. Terfenol-D is a terbium alloy that expands or contracts in the presence of a magnetic field. It has the highest magnetostriction of any alloy.[16]

Terbium oxide is used in green phosphors in fluorescent lamps and color TV tubes. Sodium terbium borate is used in solid state devices. The brilliant fluorescence allows terbium to be used as a probe in biochemistry, where it somewhat resembles calcium in its behavior. Terbium "green" phosphors (which fluoresce a brilliant lemon-yellow) are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide the trichromatic lighting technology which is by far the largest consumer of the world's terbium supply. Trichromatic lighting provides much higher light output for a given amount of electrical energy than does incandescent lighting.[3]

Terbium is also used to detect endospores, as it acts as an assay of dipicolinic acid based on photoluminescence.[17]


As with the other lanthanides, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Terbium has no known biological role.[3]


  1. ^ Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  2. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  3. ^ a b c d e f g Hammond, C. R. (2005). "The Elements". In Lide, D. R. CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 978-0-8493-0486-6.
  4. ^ "Rare-Earth Metal Long Term Air Exposure Test". Retrieved 2009-05-05.
  5. ^ Shimada, T.; Ohno, Y.; Okazaki, T.; et al. (2004). "Transport properties of C78, C90 and Dy@C82 fullerenes – nanopeapods by field effect transistors". Physica E: Low-dimensional Systems and Nanostructures. 21 (2–4): 1089–1092. Bibcode:2004PhyE...21.1089S. doi:10.1016/j.physe.2003.11.197.
  6. ^ Jackson, M. (2000). "Magnetism of Rare Earth" (PDF). The IRM Quarterly. 10 (3): 1.
  7. ^ Gruen, D.M.; Koehler, W.C.; Katz, J.J. (April 1951). "Higher Oxides of the Lanthanide Elements: Terbium Dioxide". Journal of the American Chemical Society. 73 (4): 1475–1479. doi:10.1021/ja01148a020.
  8. ^ a b c d e Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 920–921. ISBN 978-0-07-049439-8. Retrieved 2009-06-06.
  9. ^ a b c d "Chemical reactions of Terbium". Webelements. Retrieved 2009-06-06.
  10. ^ Cotton (2007). Advanced inorganic chemistry (6th ed.). Wiley-India. p. 1128. ISBN 978-81-265-1338-3.
  11. ^ Rau, J. V.; Chilingarov, N. S.; Leskiv, M. S.; Sukhoverkhov', V. F.; Rossi Albertini, V.; Sidorov, L. N. (2001). "Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine".
  12. ^ a b c d G. Audi; A. H. Wapstra; C. Thibault; J. Blachot & O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729 (1): 3–128. Bibcode:2003NuPhA.729....3A. CiteSeerX doi:10.1016/j.nuclphysa.2003.11.001. Archived from the original (PDF) on 2008-09-23.
  13. ^ a b Gupta, C. K.; Krishnamurthy, Nagaiyar (2004). Extractive metallurgy of rare earths. CRC Press. p. 5. ISBN 978-0-415-33340-5.
  14. ^ Hudson Institute of Mineralogy (1993–2018). "Mindat.org". www.mindat.org. Retrieved 14 January 2018.
  15. ^ https://www.sciencealert.com/japan-discovered-a-rare-earth-mineral-deposit-that-can-supply-the-world-for-centuries
  16. ^ Rodriguez, C; Rodriguez, M.; Orue, I.; Vilas, J.; Barandiaran, J.; Gubieda, M.; Leon, L. (2009). "New elastomer–Terfenol-D magnetostrictive composites". Sensors and Actuators A: Physical. 149 (2): 251. doi:10.1016/j.sna.2008.11.026.
  17. ^ Rosen, D. L.; Sharpless, C.; McGown, L. B. (1997). "Bacterial Spore Detection and Determination by Use of Terbium Dipicolinate Photoluminescence". Analytical Chemistry. 69 (6): 1082–1085. doi:10.1021/ac960939w.

External links

Carl Gustaf Mosander

Carl Gustaf Mosander (10 September 1797 – 15 October 1858) was a Swedish chemist. He discovered the elements lanthanum, erbium and terbium.

Dipicolinic acid

Dipicolinic acid (pyridine-2,6-dicarboxylic acid or PDC and DPA) is a chemical compound which composes 5% to 15% of the dry weight of bacterial spores. It is implicated as responsible for the heat resistance of the endospore.However, mutants resistant to heat but lacking dipicolinic acid have been isolated, suggesting other mechanisms contributing to heat resistance are at work.Dipicolinic acid forms a complex with calcium ions within the endospore core. This complex binds free water molecules, causing dehydration of the spore. As a result, the heat resistance of macromolecules within the core increases. The calcium-dipicolinic acid complex also functions to protect DNA from heat denaturation by inserting itself between the nucleobases, thereby increasing the stability of DNA.Two genera of bacterial pathogens are known to produce endospores: the aerobic Bacillus and anaerobic Clostridium.The high concentration of DPA in and specificity to bacterial endospores has long made it a prime target in analytical methods for the detection and measurement of bacterial endospores. A particularly important development in this area was the demonstration by Rosen et al. of an assay for DPA based on photoluminescence in the presence of terbium, although this phenomenon was first investigated for using DPA in an assay for terbium by Barela and Sherry. Extensive subsequent work by numerous scientists has elaborated on and further developed this approach.

It is also used to prepare dipicolinato ligated lanthanide and transition metal complexes for ion chromatography.

Isotopes of terbium

Naturally occurring terbium (65Tb) is composed of 1 stable isotope, 159Tb. Thirty-six radioisotopes have been characterized, with the most stable being 158Tb with a half-life of 180 years, 157Tb with a half-life of 71 years, and 160Tb with a half-life of 72.3 days. All of the remaining radioactive isotopes have half-lives that are less than 6.907 days, and the majority of these have half-lives that are less than 24 seconds. This element also has 27 meta states, with the most stable being 156m1Tb (t1/2 24.4 hours), 154m2Tb (t1/2 22.7 hours) and 154m1Tb (t1/2 9.4 hours).

The primary decay mode before the most abundant stable isotope, 159Tb, is electron capture, and the primary mode behind is beta decay. The primary decay products before 159Tb are element Gd (gadolinium) isotopes, and the primary products behind are element Dy (dysprosium) isotopes.

Major actinide

Major actinides is a term used in the nuclear power industry that refers to the plutonium and uranium present in used nuclear fuel, as opposed to the minor actinides neptunium, americium, curium, berkelium, and californium.

Rare-earth element

A rare-earth element (REE) or rare-earth metal (REM), as defined by IUPAC, is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Scandium and yttrium are considered rare-earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties. Rarely, a broader definition that includes actinides may be used, since the actinides share some mineralogical, chemical, and physical (especially electron shell configuration) characteristics.The 17 rare-earth elements are cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y).

Despite their name, rare-earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, more abundant than copper. However, because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals; as a result economically exploitable ore deposits are less common. The first rare-earth mineral discovered (1787) was gadolinite, a mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village of Ytterby in Sweden; four of the rare-earth elements bear names derived from this single location.

Terbium(III) bromide

Terbium(III) bromide (TbBr3) is a crystalline chemical compound.

Terbium(III) chloride

Terbium(III) chloride (TbCl3) is a chemical compound. In the solid state TbCl3 has the YCl3 layer structure. Terbium(III) chloride frequently forms a hexahydrate.

Terbium(III) iodide

Terbium(III) iodide (TbI3) is an inorganic chemical compound.

Terbium(III) nitrate

Terbium(III) nitrate is an inorganic chemical compound with the formula Tb(NO3)3. The hexahydrate crystallizes as triclinic colorless crystals with the formula [Tb(NO3)3(H2O)4]·2H2O. It can be used to synthesize materials with green emission.

Terbium(III) oxide

Terbium(III) oxide, also known as terbium sesquioxide, is a sesquioxide of the rare earth metal terbium, having chemical formula Tb2O3. It is a p-type semiconductor when doped with calcium, and may be prepared by the reduction of Tb4O7 in hydrogen at 1300 °C for 24 hours.It is a p-type semiconductor.It is a basic oxide and easily dissolved to dilute acids, and then almost colourless terbium salt is formed.

Tb2O3 + 6 H+ → 2 Tb3+ + 3 H2OThe crystal structure is cubic and the lattice constant is a = 1057 pm.

Terbium(III,IV) oxide

Terbium(III,IV) oxide, occasionally called tetraterbium heptaoxide, has the formula Tb4O7, though some texts refer to it as TbO1.75. There is some debate as to whether it is a discrete compound, or simply one phase in an interstitial oxide system. Tb4O7 is one of the main commercial terbium compounds, and the only such product containing at least some Tb(IV) (terbium in the +4 oxidation state), along with the more stable Tb(III). It is produced by heating the metal oxalate, and it is used in the preparation of other terbium compounds. Terbium forms three other major oxides: Tb2O3, TbO2, and Tb6O11.

Terbium gallium garnet

Terbium gallium garnet (TGG) is a kind of synthetic garnet, with the chemical composition Tb3Ga5O12. This is a Faraday rotator material with excellent transparency properties and is very resistant to laser damage. TGG can be used in optical isolators for laser systems, in optical circulators for fiber optic systems, in optical modulators, and in current and magnetic field sensors.

TGG has a high Verdet constant which results in the Faraday effect. The Verdet constant increases substantially as the mineral approaches cryogenic temperatures. The highest Verdet constants are found in terbium doped dense flint glasses or in crystals of TGG. The Faraday effect is chromatic (i.e. it depends on wavelength) and therefore the Verdet constant is quite a strong function of wavelength. At 632 nm, the Verdet constant for TGG is reported to be −134 rad/(T·m), whereas at 1064 nm it falls to −40 rad/(T·m). This behavior means that the devices manufactured with a certain degree of rotation at one wavelength, will produce much less rotation at longer wavelengths. Many Faraday rotators and isolators are adjustable by varying the degree to which the amount of the Faraday rotator material is inserted into the magnetic field of the device. In this way, the device can be tuned for use with a range of lasers within the design range of the device.

Terbium oxide

Terbium oxide may refer to either of the following:

Terbium(III) oxide, Tb2O3

Terbium(III,IV) oxide, Tb4O7

Terbium silicide

Terbium silicide is a chemical compound of the rare earth metal terbium with silicon having chemical formula TbSi2. It is a gray solid first described in detail in the late 1950s.The metallic resistivity and low Schottky barrier of TbSi2 (on n-type doped silicon) make it a potential candidate for applications such as infrared detectors, ohmic contacts, magnetoresistive devices, and thermoelectric devices.

It exhibits antiferromagnetism at 16K.


Terfenol-D, an alloy of the formula TbxDy1−xFe2 (x ~ 0.3), is a magnetostrictive material. It was initially developed in the 1970s by the Naval Ordnance Laboratory in United States. The technology for manufacturing the material efficiently was developed in the 1980s at Ames Laboratory under a U.S. Navy funded program. It is named after terbium, iron (Fe), Naval Ordnance Laboratory (NOL), and the D comes from dysprosium.

Thor Lake

Thor Lake is a deposit of rare metals located in the Blachford Lake intrusive complex. It is situated 5 km north of the Hearne Channel of Great Slave Lake, Northwest Territories, Canada, approximately 100 kilometers east-southeast of the capital city of Yellowknife. Geologically located on the Canadian Shield it is mostly composed of peralkaline syenite (granitic rock with low quartz content). The Blatchford Lake complex was created in the early Proterozoic, 2.14 Ga ago. The deposit is divided in several sub-structures. In a small zone at the northern edge of the syenite, the T-Zone, minerals like bastnäsite, phenakite and xenotime can be found.

Within the Mackenzie mining district, Thor Lake may contain some of the largest deposits of light and heavy rare-earth element (REE) ores. The major elements of these ores are europium, terbium, dysprosium, neodymium, gallium, niobium, thorium, zirconium and beryllium. A significant proportion of the REE deposits lie within the boundaries of the Nechalacho Rare Earth Element Project, funded by Avalon Rare Metals.

The extraction of these resources could be important for the global REE production, which almost exclusively occurs in China, especially around the Inner Mongolia Autonomous Region in Bayan Obo.

Verdet constant

The Verdet constant is an optical property named after the French physicist Émile Verdet. It describes the strength of the Faraday effect for a particular material.

The Verdet constant for most materials is extremely small and is wavelength dependent. It is strongest in substances containing paramagnetic ions such as terbium. The highest Verdet constants in bulk media are found in terbium doped dense flint glasses or in crystals of terbium gallium garnet (TGG). These materials have excellent transparency properties and high damage thresholds for laser radiation. Atomic vapours, however, can have Verdet constants which are orders of magnitude larger than TGG, but only over a very narrow wavelength range. Alkali vapours can therefore be used as an optical isolator, as demonstrated in Durham University's Atomic and Molecular Physics research group.The Faraday effect is chromatic (i.e. it depends on wavelength) and therefore the Verdet constant is quite a strong function of wavelength. At 632.8 nm, the Verdet constant for TGG is reported to be −134 rad/(T·m), whereas at 1064 nm it falls to −40 rad/(T·m). This behavior means that the devices manufactured with a certain degree of rotation at one wavelength, will produce much less rotation at longer wavelengths. Many Faraday rotators and isolators are adjustable by varying the degree to which the active TGG rod is inserted into the magnetic field of the device. In this way, the device can be tuned for use with a range of lasers within the design range of the device. Truly broadband sources (such as ultrashort-pulse lasers and the tunable vibronic lasers) will not see the same rotation across the whole wavelength band.


Ytterby (Swedish pronunciation: [²ʏtːɛrˌbyː]) is a village on the Swedish island of Resarö, in Vaxholm Municipality in the Stockholm archipelago. Today the residential area is dominated by suburban homes.

The name of the village translates to "outer village". Ytterby is perhaps most famous for having the single richest source of elemental discoveries in the world; the chemical elements Yttrium (Y), Ytterbium (Yb), Erbium (Er) and Terbium (Tb) are all named after Ytterby.

Terbium compounds

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