Terbium
Encyclopedia
Terbium is a chemical element
with the 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. Terbium is never found in nature as a free element, but it is contained in many mineral
s, including cerite
, gadolinite
, monazite
, xenotime
and euxenite
.
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 cell
s 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 actuator
s, in naval sonar
systems and in sensor
s.
The largest consumer of the world's terbium supply is in "green" phosphors (which are usually yellow). Terbium oxide
is in fluorescent lamp
s and TV tubes. Terbium "green" phosphor
s (which fluoresce a brilliant lemon-yellow) 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.
metal
that is malleable, ductile and soft enough to be cut with a knife. It is relatively stable in air as compared to other lanthanides. Terbium exists in two crystal allotropes
with a transformation temperature of 1289 °C between them.
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 Tb atoms have been isolated by implanting them into fullerene
molecules.
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.
. The +4 state is known in TbO2 and TbF4.
Terbium burns readily to form a mixed terbium(III,IV) oxide
:
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:
Terbium metal reacts with all the halogens, forming white trihalides:
Terbium dissolves readily in dilute sulfuric acid
to form solutions containing the pale pink terbium(III) ions, which exist as a [Tb(OH2)9]3+ complexes:
Other compounds include
Terbium(IV) fluoride is a strong fluorinating agent, emitting relatively pure atomic fluorine when heated rather than the mixture of fluoride vapors emitted from CoF3 or CeF4.
, terbium-159; the element is thus called mononuclidic and monoisotopic
. 36 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). The most stable synthetic radioisotope
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 well less than quarter a year, and the majority of these have half-lives that are less than half a minute. 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.
The element also has 27 nuclear isomer
s, 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.
chemist
Carl Gustaf Mosander
,
who detected it as an impurity in Yttrium oxide, Y2O3, and named after the village Ytterby
in Sweden
. It was not isolated in pure form until the recent advent of ion exchange
techniques.
When Mosander first partitioned "yttria" into three fractions, "terbia" was the fraction that contained the pink color (due to what is now known as erbium), and "erbia" was the fraction that was essentially colorless in solution, but gave a brown-tinged oxide. Later workers had difficulty in observing the latter, but the 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. It is now thought that those workers who used the double sodium or potassium sulfates to remove "ceria" from "yttria" inadvertently lost the terbium content of the system into the ceria-containing precipitate. In any case, 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 oxide. Thus, terbium was a minor component in the original terbium fraction, 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 it was pure. The 19th century investigators did not have the benefit of fluorescence technology, wherewith to observe the brilliant fluorescence that would have made this element much easier to track in mixtures.
Terbium is never found in nature by itself, but 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.
Currently, the richest commercial sources of terbium are the ion-adsorption clay
s 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.
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 oxalate
s. 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. Terbium is separated as a double salt with ammonium nitrate by crystallization.
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
.
in calcium fluoride
, calcium tungstate
and strontium
molybdate
, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cell
s which operate at elevated temperatures, together with ZrO2.
Terbium is also used in alloy
s and in the production of electronic devices. As a component of Terfenol-D
, terbium is of use in actuator
s, in naval sonar
systems, sensor
s, in the SoundBug
device (its first commercial application), and other magnetomechanical devices. Terfenol-D is an alloy that expands or contracts in the presence of a magnetic field. It has the highest magnetostriction
of any alloy
.
Terbium oxide
is used in green phosphor
s 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.
s, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Terbium has no known biological role.
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with the symbol Tb and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
65. It is a silvery-white rare earth
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
that is malleable, ductile and soft enough to be cut with a knife. Terbium is never found in nature as a free element, but it is contained in many mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s, including cerite
Cerite
Cerite is a complex silicate mineral group containing cerium, formula 963. The cerium and lanthanum content varies with the Ce rich species and the La rich species...
, gadolinite
Gadolinite
Gadolinite, sometimes also known as Ytterbite, is a silicate mineral which consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula 2FeBe2Si2O10...
, monazite
Monazite
Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral:...
, xenotime
Xenotime
Xenotime is a rare earth phosphate mineral, whose major component is yttrium orthophosphate . It forms a solid solution series with chernovite- and therefore may contain trace impurities of arsenic, as well as silicon dioxide and calcium...
and euxenite
Euxenite
Euxenite or euxenite- is a brownish black mineral with a metallic luster.-Chemistry:It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6...
.
Terbium is used to dope
Dopant
A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance in order to alter the electrical properties or the optical properties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that...
calcium fluoride
Calcium fluoride
Calcium fluoride is the inorganic compound with the formula CaF2. This ionic compound of calcium and fluorine occurs naturally as the mineral fluorite . It is the source of most of the world's fluorine. This insoluble solid adopts a cubic structure wherein calcium is coordinated to eight fluoride...
, calcium tungstate
Tungstate
In chemistry a tungstate is a compound that contains an oxoanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is WO42−, "orthotungstate"...
and strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
molybdate
Molybdate
In chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state.The...
, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
s which operate at elevated temperatures. As a component of Terfenol-D
Terfenol-D
Terfenol-D, an alloy of the formula x1-x is a magnetostrictive material. It was initially developed in the 1970s by the Naval Ordnance Laboratory in North America. The technology for manufacturing the material efficiently was developed in the 1980s at Ames Laboratory under a U.S. Navy funded...
(an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuator
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
s, in naval sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
systems and in sensor
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
s.
The largest consumer of the world's terbium supply is in "green" phosphors (which are usually yellow). Terbium oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
is in fluorescent lamp
Fluorescent lamp
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
s and TV tubes. Terbium "green" phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s (which fluoresce a brilliant lemon-yellow) are combined with divalent europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
blue phosphors and trivalent europium red phosphors to provide "trichromatic" lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.
Physical properties
Terbium is a silvery-white rare earthRare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
that is malleable, ductile and soft enough to be cut with a knife. It is relatively stable in air as compared to other lanthanides. Terbium exists in two crystal allotropes
Allotropy
Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, known as allotropes of these elements...
with a transformation temperature of 1289 °C between them.
The terbium(III) cation is brilliantly fluorescent
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
, 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
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
owes its creamy-yellow fluorescence in part to terbium. Terbium easily oxidizes, and is therefore used in its elemental form specifically for research. Single Tb atoms have been isolated by implanting them into fullerene
Fullerene
A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and they resemble the balls used in association football. Cylindrical ones are called carbon nanotubes or buckytubes...
molecules.
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.
Chemical properties
The most common valence state of terbium is +3, as inTerbium(III) oxide
Terbium oxide, also known as terbium sesquioxide, is a sesquioxide of the rare earth metal terbium, having chemical formula . It is a p-type semiconductor when doped with calcium, and may be prepared by the reduction of in hydrogen at 1300 °C for 24 hours.It is a p-type semiconductor.It is a basic...
. The +4 state is known in TbO2 and TbF4.
Terbium burns readily to form a mixed terbium(III,IV) oxide
Terbium(III,IV) oxide
Terbium 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...
:
- 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:
- 2 Tb + 6 H2O → 2 Tb(OH)3 + 3 H2↑
Terbium metal reacts with all the halogens, forming white trihalides:
- 2 Tb + 3 X2 → 2 TbX3 (X = FFluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
, ClChlorineChlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, BrBromineBromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
, IIodineIodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
)
Terbium dissolves readily in dilute sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
to form solutions containing the pale pink terbium(III) ions, which exist as a [Tb(OH2)9]3+ complexes:
- 2 Tb (s) + 3 H2SO4 → 2 Tb3+ + 3 + 3 H2↑
Compounds
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. In those compounds, Tb mostly exhibit 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.Other compounds include
- ChlorideChlorideThe chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
s: TbCl3Terbium(III) chlorideTerbium chloride is a chemical compound. In the solid state TbCl3 has the YCl3 layer structure. Terbium chloride frequently forms a hexahydrate.-Hazards:Terbium chloride causes hyperemia of the iris.... - BromideBromideA bromide is a chemical compound containing bromide ion, that is bromine atom with effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.-Natural occurrence:...
s: TbBr3Terbium(III) bromideTerbium bromide is a chemical compound.... - IodideIodideAn iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...
s: TbI3Terbium(III) iodideTerbium iodide is an inorganic chemical compound.... - FluorideFluorideFluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
s: TbF3, TbF4
Terbium(IV) fluoride is a strong fluorinating agent, emitting relatively pure atomic fluorine when heated rather than the mixture of fluoride vapors emitted from CoF3 or CeF4.
Isotopes
Naturally occurring terbium is composed of its only stable isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
, terbium-159; the element is thus called mononuclidic and monoisotopic
Monoisotopic element
A monoisotopic element is one of 26 chemical elements which have only a single stable isotope . A list is given in a following section....
. 36 radioisotopes have been characterized, with the heaviest being terbium-171 (with atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....
of 170.95330(86) u) and lightest being terbium-135 (exact mass unknown). The most stable synthetic radioisotope
Synthetic radioisotope
A synthetic radioisotope is a radionuclide that is not found in nature: no natural process or mechanism exists which produces it, or it is so unstable that it decays away in a very short period of time. Examples include technetium-95 and promethium-146. Many of these are found in, and harvested...
of terbium are terbium-158, with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 180 years, and terbium-157, with a half-life of 71 years. All of the remaining radioactive isotopes have half-lives that are well less than quarter a year, and the majority of these have half-lives that are less than half a minute. The primary decay mode before the most abundant stable isotope, 159Tb, is electron capture
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
, which results in production of gadolinium
Gadolinium
Gadolinium is a chemical element with the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined form. Gadolinium was first detected spectroscopically in 1880 by de Marignac who separated its oxide and is credited with...
isotopes, and the primary mode after is beta minus decay, resulting in dysprosium
Dysprosium
Dysprosium is a chemical element with the symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime...
isotopes.
The element also has 27 nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
s, 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.
History
Terbium was discovered in 1843 by SwedishSweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
chemist
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...
Carl Gustaf Mosander
Carl Gustaf Mosander
Carl Gustaf Mosander was a Swedish chemist. He discovered the elements lanthanum, erbium and terbium....
,
who detected it as an impurity in Yttrium oxide, Y2O3, and named after the village Ytterby
Ytterby
Ytterby is a village on the Swedish island of Resarö, in Vaxholm Municipality in the Stockholm archipelago.The name of the village means "outer village", implying that its location is its most noteworthy feature....
in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
. It was not isolated in pure form until the recent advent of ion exchange
Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
techniques.
When Mosander first partitioned "yttria" into three fractions, "terbia" was the fraction that contained the pink color (due to what is now known as erbium), and "erbia" was the fraction that was essentially colorless in solution, but gave a brown-tinged oxide. Later workers had difficulty in observing the latter, but the 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. It is now thought that those workers who used the double sodium or potassium sulfates to remove "ceria" from "yttria" inadvertently lost the terbium content of the system into the ceria-containing precipitate. In any case, 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 oxide. Thus, terbium was a minor component in the original terbium fraction, dominated by its immediate neighbors, gadolinium
Gadolinium
Gadolinium is a chemical element with the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined form. Gadolinium was first detected spectroscopically in 1880 by de Marignac who separated its oxide and is credited with...
and dysprosium
Dysprosium
Dysprosium is a chemical element with the symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime...
. Thereafter, whenever other rare earths were teased apart from this mixture, whichever fraction gave the brown oxide retained the terbium name, until at last it was pure. The 19th century investigators did not have the benefit of fluorescence technology, wherewith to observe the brilliant fluorescence that would have made this element much easier to track in mixtures.
Occurrence
Monazite
Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral:...
((Ce,La,Th,Nd,Y)PO4 with up to 0.03% terbium), xenotime
Xenotime
Xenotime is a rare earth phosphate mineral, whose major component is yttrium orthophosphate . It forms a solid solution series with chernovite- and therefore may contain trace impurities of arsenic, as well as silicon dioxide and calcium...
(YPO4) and euxenite
Euxenite
Euxenite or euxenite- is a brownish black mineral with a metallic luster.-Chemistry:It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6...
((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.
Currently, the richest commercial sources of terbium are the ion-adsorption clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s of southern China; the concentrates with about two-thirds yttrium oxide by weight have about 1% terbia. Small amounts of terbium occur in bastnäsite
Bastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
and monazite; when these are processed by solvent extraction to recover the valuable heavy lanthanides as samarium
Samarium
Samarium is a chemical element with the symbol Sm, atomic number 62 and atomic weight 150.36. It is a moderately hard silvery metal which readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3...
-europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
-gadolinium
Gadolinium
Gadolinium is a chemical element with the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined form. Gadolinium was first detected spectroscopically in 1880 by de Marignac who separated its oxide and is credited with...
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.
Production
Crushed terbium-containing minerals are treated with hot concentrated sulfuric acidSulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with caustic soda to pH 3-4. Thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate
Ammonium oxalate
Ammonium oxalate, C2H8N2O4, is an oxalate salt with ammonia. It is a constituent of some types of kidney stone. Found also in guano....
to convert rare earths into their insoluble oxalate
Oxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...
s. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
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.
The most efficient separation routine for terbium salt from the rare-earth salt solution is ion exchange
Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
. 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
Zone melting
Zone melting is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal...
.
Applications
Terbium is used as a DopantDopant
A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance in order to alter the electrical properties or the optical properties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that...
in calcium fluoride
Calcium fluoride
Calcium fluoride is the inorganic compound with the formula CaF2. This ionic compound of calcium and fluorine occurs naturally as the mineral fluorite . It is the source of most of the world's fluorine. This insoluble solid adopts a cubic structure wherein calcium is coordinated to eight fluoride...
, calcium tungstate
Tungstate
In chemistry a tungstate is a compound that contains an oxoanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is WO42−, "orthotungstate"...
and strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
molybdate
Molybdate
In chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state.The...
, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
s which operate at elevated temperatures, together with ZrO2.
Terbium is also used in alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
s and in the production of electronic devices. As a component of Terfenol-D
Terfenol-D
Terfenol-D, an alloy of the formula x1-x is a magnetostrictive material. It was initially developed in the 1970s by the Naval Ordnance Laboratory in North America. The technology for manufacturing the material efficiently was developed in the 1980s at Ames Laboratory under a U.S. Navy funded...
, terbium is of use in actuator
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
s, in naval sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
systems, sensor
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
s, in the SoundBug
SoundBug
Soundbug is a small speaker that can turn a resonant flat surface into a flat panel speaker. The Soundbug is attached to a smooth resonant surface, this surface then acts as speaker. The tone differs depending on the surface...
device (its first commercial application), and other magnetomechanical devices. Terfenol-D is an alloy that expands or contracts in the presence of a magnetic field. It has the highest magnetostriction
Magnetostriction
Magnetostriction is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of material's magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ...
of any alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
.
Terbium oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
is used in green phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s in fluorescent lamps and color TV tubes. Sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
terbium borate
Borate
Borates are chemical compounds which contain oxoanions of boron in oxidation state +3. The simplest borate ion, BO33−, has a trigonal planar structure. Other borates are made up of trigonal BO3 or tetrahedral BO4 structural units, sharing oxygen atoms...
is used in solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
devices. The brilliant fluorescence allows terbium to be used as a probe in biochemistry, where it somewhat resembles calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
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.
Precautions
As with the other lanthanideLanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
s, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. Terbium has no known biological role.