Terbium#Characteristics

Terbium is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife. It is relatively stable in air compared to the more reactive lanthanides in the first half of the lanthanide series.{{cite web| url = http://www.elementsales.com/re_exp/index.htm |title = Rare-Earth Metal Long Term Air Exposure Test| access-date = 2009-05-05}} Terbium exists in two crystal allotropes with a transformation temperature of 1289 °C between them. The 65 electrons of a terbium atom are arranged in the electron configuration [Xe]4f⁹6s². The eleven 4f and 6s electrons are valence. 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.

The terbium(III) cation (Tb³⁺) 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. Trivalent europium (Eu³⁺) and Tb³⁺ ions are among the lanthanide ions that have garnered the most attention because of their strong luminosity and great color purity.V.B. Taxak, R. Kumar, J.K. Makrandi, S.P. Khatkar Displays, 30 (2009), pp. 170–174{{cite journal|last1=Shimada|first1=T.|last2=Ohno|first2=Y.|last3=Okazaki|first3=T.|last4=Sugai|first4=T.|last5=Suenaga|first5=K.|last6=Kishimoto|first6=S.|last7=Mizutani|first7=T.|last8=Inoue|first8=T.|last9=Taniguchi|first9=R.|last10=Fukui|display-authors=3 | first10=N.|last11=Okubo | first11=H.|last12=Shinohara | first12=H.|title=Transport properties of C₇₈, C₉₀ and Dy@C₈₂ fullerenes – nanopeapods by field effect transistors|journal=Physica E: Low-dimensional Systems and Nanostructures|year=2004|volume=21|issue=2–4|pages=1089–1092|doi=10.1016/j.physe.2003.11.197|bibcode = 2004PhyE...21.1089S}}

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 antiferromagnetism transforms into a disordered paramagnetic state at 230 K.{{cite journal| author =Jackson, M. | title =Magnetism of Rare Earth| url =http://www.irm.umn.edu/quarterly/irmq10-3.pdf | journal = The IRM Quarterly | volume =10| issue = 3| page = 1| date = 2000}}

Terbium metal is an electropositive element and oxidizes in the presence of most acids (such as sulfuric acid), all of the halogens, and water.

:{{chem2|2 Tb (s) + 3 H2SO4 → 2 Tb(3+) + 3 SO4(2-) + 3 H2↑}}

:{{chem2|1=2 Tb + 3 X2 → 2 TbX3 (X = F, Cl, Br, I)}}

:{{chem2|2 Tb (s) + 6 H2O → 2 Tb(OH)3 + 3 H2↑}}

Terbium oxidizes readily in air to form a mixed terbium(III,IV) oxide:{{cite web| url =https://www.webelements.com/terbium/chemistry.html| title =Chemical reactions of Terbium| publisher=Webelements| access-date=2009-06-06}}

:{{chem2|8 Tb + 7 O2 → 2 Tb4O7}}

The most common oxidation state of terbium is +3 (trivalent), such as in Terbium trichloride. In the solid state, tetravalent terbium is also known, in compounds such as terbium oxide ({{chem2|TbO2}}) and terbium tetrafluoride.{{cite journal|title=Higher Oxides of the Lanthanide Elements: Terbium Dioxide|author=Gruen, D. M. |author2=Koehler, W. C. |author3=Katz, J. J. |date=April 1951|pages=1475–1479|volume=73|journal=Journal of the American Chemical Society|doi=10.1021/ja01148a020|issue=4|bibcode=1951JAChS..73.1475G }} In solution, terbium typically forms trivalent species, but can be oxidized to the tetravalent state with ozone in highly basic aqueous conditions.{{cite journal |title=Stabilization of Praseodymium(IV) and Terbium(IV) in Aqueous Carbonate Solution |author1=Hobart, D. E. |author2= Samhoun, K. |author3= Young, J. P. |author4=Norvell, V. E. |author5= Mamantov, G. |author6= Peterson, J. R. |date=1980 |pages=321–328 |volume=16 |journal=Inorganic and Nuclear Chemistry Letters |doi=10.1016/0020-1650(80)80069-9 |issue=5}}

The coordination and organometallic chemistry of terbium is similar to other lanthanides. In aqueous conditions, terbium can be coordinated by nine water molecules, which are arranged in a tricapped trigonal prismatic molecular geometry.{{Cite journal |last1=Zhuang |first1=Jia-Jia |last2=Chen |first2=Ming-Guang |last3=Sun |first3=Yan-Bing |last4=Hang |first4=Pei |last5=Sui |first5=Yang |last6=Tong |first6=Jia-Ping |date=2020-03-01 |title=Synthesis, Structure and Magnetic Property of a Tricapped Trigonal Prismatic Tb^III-Based 3d-4f Complex |journal=IOP Conference Series: Materials Science and Engineering |volume=774 |issue=1 |pages=012042 |doi=10.1088/1757-899X/774/1/012042 |issn=1757-8981|doi-access=free |bibcode=2020MS&E..774a2042Z }} Complexes of terbium with lower coordination number are also known, typically with bulky ligands like bis(trimethylsilyl)amide, which forms the three-coordinate tris[N,N-bis(trimethylsilyl)amide]terbium(III) ({{chem2|Tb[N(SiMe3)2]3}}) complex.{{Cite journal |last1=Boyde |first1=Nicholas C. |last2=Chmely |first2=Stephen C. |last3=Hanusa |first3=Timothy P. |last4=Rheingold |first4=Arnold L. |last5=Brennessel |first5=William W. |date=2014-09-15 |title=Structural Distortions in M[E(SiMe₃)₂]₃ Complexes (M = Group 15, f-Element; E = N, CH): Is Three a Crowd? |url=https://pubs.acs.org/doi/10.1021/ic501232z |journal=Inorganic Chemistry |language=en |volume=53 |issue=18 |pages=9703–9714 |doi=10.1021/ic501232z |pmid=25171144 |issn=0020-1669}}

Most coordination and organometallic complexes contain terbium in the trivalent oxidation state. Divalent Tb²⁺ complexes are also known, usually with bulky cyclopentadienyl-type ligands.{{cite journal |title=Tetramethylcyclopentadienyl Ligands Allow Isolation of Ln(II) Ions across the Lanthanide Series in [K(2.2.2-cryptand)][(C₅Me₄H)₃Ln] Complexes |author1=Jenkins, T. F. |author2= Woen, D. H |author3= Mohanam, L. N. |author4=Ziller, J. W. |author5=Furche, F. |author6=Evans, W. J. |date=2018|pages=3863–3873|volume=141 |journal=Organometallics |doi=10.1021/acs.organomet.8b00557 |issue=21|s2cid=105379627 }}{{cite journal |title=Completing the Series of +2 Ions for the Lanthanide Elements: Synthesis of Molecular Complexes of Pr²⁺, Gd²⁺, Tb²⁺, and Lu²⁺ |author1=Macdonald, M. R. |author2= Bates, J. E. |author3= Ziller, J. W. |author4=Furche, F. |author5=Evans, W. J. |date=2013|pages=9857–9868|volume=135|journal=Journal of the American Chemical Society|doi=10.1021/ja403753j|issue=21|pmid=23697603 |bibcode=2013JAChS.135.9857M }}{{Cite journal|last1=Gould|first1=C. A.|last2=McClain|first2=K. R. |last3=Yu|first3=J. M.|last4=Groshens|first4=T. J.|last5=Furche|first5=F. P.|last6=Harvey|first6=B. G.|last7=Long|first7=J. R.|date=2019-08-21|title=Synthesis and Magnetism of Neutral, Linear Metallocene Complexes of Terbium(II) and Dysprosium(II)|journal=Journal of the American Chemical Society|volume=141|issue=33|pages=12967–12973|doi=10.1021/jacs.9b05816|pmid=31375028|bibcode=2019JAChS.14112967G |s2cid=199388151|issn=0002-7863}} A few coordination compounds containing terbium in its tetravalent state are also known.{{cite journal |title=Molecular Complex of Tb in the +4 Oxidation State |author1=Palumbo, C. T. |author2=Zivkovic, I. |author3=Scopelliti, R. |author4=Mazzanti, M. |date=2019 |pages=9827–9831 |volume=141 |journal=Journal of the American Chemical Society |doi=10.1021/jacs.9b05337 |pmid=31194529 |issue=25 |bibcode=2019JAChS.141.9827P |s2cid=189814301 |url=http://infoscience.epfl.ch/record/268286/files/Palumbo%20ja-2019-05337d%20manuscriptR1.pdf |archive-url=https://web.archive.org/web/20240423040613/https://infoscience.epfl.ch/record/268286/files/Palumbo%20ja-2019-05337d%20manuscriptR1.pdf |url-status=dead |archive-date=April 23, 2024 }}{{Cite journal|last1=Rice|first1=N. T.|last2=Popov|first2=I. A.|last3=Russo|first3=D. R.|last4=Bacsa|first4=J.|last5=Batista|first5=E. R.|last6=Yang|first6=P.|last7=Telser|first7=J.|last8=La Pierre|first8=H. S.|date=2019-08-21|title=Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex|journal=Journal of the American Chemical Society|volume=141|issue=33|pages=13222–13233|doi=10.1021/jacs.9b06622|pmid=31352780|bibcode=2019JAChS.14113222R |osti=1558225|s2cid=207197096|issn=0002-7863|url=https://figshare.com/articles/journal_contribution/9450461 }}{{cite journal |title= Stabilization of the Oxidation State +IV in Siloxide-Supported Terbium Compounds |author1=Willauer, A. R. |author2=Palumbo, C. T. |author3=Scopelliti, R. |author4=Zivkovic, I. |author5=Douair, I. |author6=Maron, L. |author7=Mazzanti, M. |date=2020 |pages=3549–3553|volume=59 |journal=Angewandte Chemie International Edition |issue=9 |doi=10.1002/anie.201914733|pmid=31840371 |s2cid=209385870 |url=https://infoscience.epfl.ch/record/275738/files/Mazzanti_et_al-2019-Angewandte_Chemie_International_Edition-2.pdf }}

Like most rare-earth elements and lanthanides, terbium is usually found in the +3 oxidation state. Like cerium and praseodymium, terbium can also form a +4 oxidation state,{{Cite journal |last1=Palumbo |first1=Chad T. |last2=Zivkovic |first2=Ivica |last3=Scopelliti |first3=Rosario |last4=Mazzanti |first4=Marinella |date=2019-06-26 |title=Molecular Complex of Tb in the +4 Oxidation State |url=https://pubs.acs.org/doi/10.1021/jacs.9b05337 |journal=Journal of the American Chemical Society |language=en |volume=141 |issue=25 |pages=9827–9831 |doi=10.1021/jacs.9b05337 |pmid=31194529 |bibcode=2019JAChS.141.9827P |issn=0002-7863}} although it is unstable in water.{{Greenwood&Earnshaw2nd}} It is possible for terbium to be found in the 0,{{cite journal |last=Cloke |first=F. Geoffrey N. |date=1993 |title=Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides |journal=Chem. Soc. Rev. |volume=22 |pages=17–24 |doi=10.1039/CS9932200017}}{{cite journal |last1=Arnold |first1=Polly L. |last2=Petrukhina |first2=Marina A. |last3=Bochenkov |first3=Vladimir E. |last4=Shabatina |first4=Tatyana I. |last5=Zagorskii |first5=Vyacheslav V. |last6=Cloke |first9=F. Geoffrey N. |date=2003-12-15 |title=Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation |journal=Journal of Organometallic Chemistry |volume=688 |issue=1–2 |pages=49–55 |doi=10.1016/j.jorganchem.2003.08.028}} +1,{{cite journal |last1=Li |first1=Wan-Lu |last2=Chen |first2=Teng-Teng |last3=Chen |first3=Wei-Jia |last4=Li |first4=Jun |last5=Wang |first5=Lai-Sheng |year=2021 |title=Monovalent lanthanide(I) in borozene complexes |journal=Nature Communications |volume=12 |issue=1 |page=6467 |bibcode=2021NatCo..12.6467L |doi=10.1038/s41467-021-26785-9 |pmc=8578558 |pmid=34753931}} and +2 oxidation states.

{{Main article|Terbium compounds}}

{{multiple image | direction = vertical | width = 200

|align=right

|image1=Tb-sulfate.jpg

|image2=Tb-sulfate-luminescence.jpg

|caption2=Terbium sulfate, {{chem2|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 {{chem2|TbH2}}, {{chem2|TbH3}}, {{chem2|TbB2}}, {{chem2|Tb2S3}}, {{chem2|TbSe}}, {{chem2|TbTe}} and {{chem2|TbN}}. In these compounds, terbium mainly exhibits the oxidation state +3, with the +2 state appearing rarely. Terbium(II) halides are obtained by annealing terbium(III) halides in presence of metallic terbium in tantalum containers. Terbium also forms the sesquichloride {{chem2|Tb2Cl3}}, which can be further reduced to terbium(I) chloride ({{Chem2|TbCl}}) by annealing at 800 °C; this compound forms platelets with layered graphite-like structure.{{cite book| page=1128| url=https://books.google.com/books?id=U3MWRONWAmMC&pg=PA1128| title =Advanced inorganic chemistry| edition =6th| author= Cotton| publisher= Wiley-India| date = 2007| isbn =978-81-265-1338-3}}

Terbium(IV) fluoride ({{Chem2|TbF4}}) is the only halide that tetravalent terbium can form. It has strong oxidizing properties and is a strong fluorinating agent, emitting relatively pure atomic fluorine when heated, rather than the mixture of fluoride vapors emitted from cobalt(III) fluoride or cerium(IV) fluoride.{{cite journal |last1=Rau |first1=J. V. |last2=Chilingarov |first2=N. S. |last3=Leskiv |first3=M. S. |last4=Sukhoverkhov |first4=V. F. |last5=Rossi Albertini |first5=V. |last6=Sidorov |first6=L. N. |title=Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine |journal=Le Journal de Physique IV |date=August 2001 |volume=11 |issue=PR3 |pages=Pr3–109–Pr3-113 |doi=10.1051/jp4:2001314}} It can be obtained by reacting terbium(III) chloride or terbium(III) fluoride with fluorine gas at 320 °C:{{Cite book|author=G. Meyer |author2=Lester R. Morss |title= Synthesis of Lanthanide and Actinide Compounds |publisher=Springer Science & Business Media|year= 1991|page=60|isbn= 978-0-7923-1018-1 |url = https://books.google.com/books?id=bnS5elHL2w8C&pg=PA60}}

: 2 TbF₃ + F₂ → 2 TbF₄

When {{Chem2|TbF4}} and caesium fluoride (CsF) is mixed in a stoichiometric ratio in a fluorine gas atmosphere, caesium pentafluoroterbate ({{Chem2|CsTbF5}}) is obtained. It is an orthorhombic crystal with space group Cmca and a layered structure composed of [TbF₈]⁴⁻ and 11-coordinated Cs⁺.{{cite journal|last1=Gaumet|first1=V.|last2=Avignant|first2=D.|title=Caesium Pentafluoroterbate, CsTbF₅|journal=Acta Crystallographica Section C: Crystal Structure Communications|volume=53|issue=9|year=1997|pages=1176–1178 |doi=10.1107/S0108270197005556|bibcode=1997AcCrC..53.1176G }} The compound barium hexafluoroterbate ({{Chem2|BaTbF6}}), an orthorhombic crystal with space group Cmma, can be prepared in a similar method. The terbium fluoride ion [TbF₈]⁴⁻{{cite journal|last1=Largeau|first1=E.|last2=El-Ghozzi|first2=M.|last3=Métin|first3=J.|last4=Avignant|first4=D.|title=β-BaTbF6|journal=Acta Crystallographica Section C: Crystal Structure Communications|volume=53|issue=5|year=1997|pages=530–532 |doi=10.1107/S0108270196014527|bibcode=1997AcCrC..53..530L }} also exists in the structure of potassium terbium fluoride crystals.{{Cite journal |last1=Balodhi |first1=Ashiwini |last2=Chang |first2=Kelvin |last3=Stevens |first3=Kevin T. |last4=Chakrapani |first4=Sunil K. |last5=Ennaceur |first5=Susan M. |last6=Migliori |first6=Albert |last7=Zevalkink |first7=Alexandra |date=2020-10-26 |title=Determination of single crystal elastic moduli of KTb₃F₁₀ by resonant ultrasound spectroscopy |url=https://pubs.aip.org/aip/jap/article/128/16/165104/568450/Determination-of-single-crystal-elastic-moduli-of |journal=Journal of Applied Physics |volume=128 |issue=16 |doi=10.1063/5.0024723 |bibcode=2020JAP...128p5104B |issn=0021-8979}}{{Cite journal |last1=Valiev |first1=Uygun V. |last2=Karimov |first2=Denis N. |last3=Ma |first3=Chong-Geng |last4=Sultonov |first4=Odiljon Z. |last5=Pelenovich |first5=Vasiliy O. |date=2022-11-12 |title=Tb³⁺ Ion Optical and Magneto-Optical Properties in the Cubic Crystals KTb₃F₁₀ |journal=Materials |language=en |volume=15 |issue=22 |pages=7999 |doi=10.3390/ma15227999 |issn=1996-1944 |pmc=9693278 |pmid=36431487 |doi-access=free|bibcode=2022Mate...15.7999V }}

Terbium(III) oxide or terbia is the main oxide of terbium, and appears as a dark brown water-insoluble solid. It is slightly hygroscopic{{Cite book |last1=Larrañaga |first1=Michael D. |url=https://onlinelibrary.wiley.com/doi/book/10.1002/9781119312468 |title=Hawley's Condensed Chemical Dictionary |last2=Lewis |first2=Richard J. |last3=Lewis |first3=Robert A. |date=September 2016 |publisher=Wiley |isbn=978-1-118-13515-0 |edition=16th |pages=1310 |language=en |doi=10.1002/9781119312468}} and is the main terbium compound found in rare earth-containing minerals and clays.

Other compounds include:

• Chlorides: {{chem2|TbCl3}}
• Bromides: {{chem2|TbBr3}}
• Iodides: {{chem2|TbI3}}
• Fluorides: {{chem2|TbF3}}, {{chem2|TbF4}}

{{Main|Isotopes of terbium}}

Naturally occurring terbium is composed of its only stable isotope, terbium-159; the element is thus mononuclidic and monoisotopic. Thirty-nine radioisotopes have been characterized,{{AME2020 II|ref}} with the heaviest being terbium-174 and lightest being terbium-135 (both with unknown exact mass).{{NUBASE2020|ref}} 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 less than three months, and the majority of these have half-lives that are less than half a minute.{{NUBASE2020|ref}} The primary decay mode before the most abundant stable isotope, {{sup|159}}Tb, is electron capture, which results in production of gadolinium isotopes, and the primary mode after is beta minus decay, resulting in dysprosium isotopes.{{NUBASE2020|ref}}

The element also has 31 nuclear isomers, with masses of 141–154, 156, 158, 162, and 164–168 (not every mass number corresponds to only one isomer).{{AME2020 II|ref}} The most stable of them are terbium-156m, with a half-life of 24.4 hours, and terbium-156m2, with a half-life of 22.7 hours; this is longer than half-lives of most ground states of radioactive terbium isotopes, except those with mass numbers 155–161.{{NUBASE2020|ref}}

Terbium-149, with a half-life of 4.1 hours, is a promising candidate in targeted alpha therapy and positron emission tomography.{{cite journal | last1=Müller | first1=Cristina | last2=Vermeulen | first2=Christiaan | last3=Köster | first3=Ulli | last4=Johnston | first4=Karl | last5=Türler | first5=Andreas | last6=Schibli | first6=Roger | last7=van der Meulen | first7=Nicholas P. | title=Alpha-PET with terbium-149: evidence and perspectives for radiotheragnostics | journal=EJNMMI Radiopharmacy and Chemistry | publisher=Springer Science and Business Media LLC | volume=1 | issue=1 | date=2016-03-28 | page=5 | issn=2365-421X | doi=10.1186/s41181-016-0008-2| pmid=29564382 | pmc=5843804 | doi-access=free }}{{cite journal | last1=Eychenne | first1=Romain | last2=Chérel | first2=Michel | last3=Haddad | first3=Férid | last4=Guérard | first4=François | last5=Gestin | first5=Jean-François | title=Overview of the Most Promising Radionuclides for Targeted Alpha Therapy: The "Hopeful Eight" | journal=Pharmaceutics | publisher=MDPI AG | volume=13 | issue=6 | date=2021-06-18 | issn=1999-4923 | doi=10.3390/pharmaceutics13060906 | page=906 | pmid=34207408 | pmc=8234975 | doi-access=free }}

File:Mosander Carl Gustav bw.jpg, the scientist who discovered terbium, lanthanum and erbium]]

Swedish chemist Carl Gustaf Mosander discovered terbium in 1843.{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Rare Earths–The Beginnings |journal=The Hexagon |date=2015 |pages=41–45 |url=http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20I.pdf |access-date=30 December 2019}}{{cite journal |last1=Marshall |first1=James L. Marshall |last2=Marshall |first2=Virginia R. Marshall |title=Rediscovery of the elements: The Rare Earths–The Confusing Years |journal=The Hexagon |date=2015 |pages=72–77 |url=http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20II.pdf |access-date=30 December 2019}} He detected it as an impurity in yttrium oxide, {{chem2|Y2O3}}, then known as yttria. Yttrium, erbium, and terbium are all named after the village of Ytterby in Sweden.{{Unbulleted list citebundle|{{cite journal | author = Weeks, Mary Elvira |author-link=Mary Elvira Weeks| title = The discovery of the elements: XVI. The rare earth elements | journal = Journal of Chemical Education | year = 1932 | volume = 9 | issue = 10 | pages = 1751–1773 | doi = 10.1021/ed009p1751 | bibcode=1932JChEd...9.1751W}}|{{cite book |last1=Weeks |first1=Mary Elvira |url=https://archive.org/details/discoveryoftheel002045mbp |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |edition=6th |location=Easton, PA |pages=705–706}}}}{{cite book |last1=Marshall |first1=James L. |title=Science history: a traveler's guide |last2=Marshall |first2=Virginia R. |date=October 31, 2014 |publisher=ACS Symposium Series |isbn=978-0-8412-3020-0 |volume=1179 |pages=209–257 |chapter=Northern Scandinavia: An Elemental Treasure Trove |doi=10.1021/bk-2014-1179.ch011}} Terbium was not isolated in pure form until the advent of ion exchange techniques.{{cite book |author=Gupta, C. K. |url=https://books.google.com/books?id=E1npz8pwmYwC&pg=PA5 |title=Extractive metallurgy of rare earths |author2=Krishnamurthy, Nagaiyar |date=2004 |publisher=CRC Press |isbn=978-0-415-33340-5 |page=5}}

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", the oxide containing what is now known as terbium, originally was the fraction that was yellow or dark orange in solution. The insoluble oxide of this element was noted to be tinged brown,{{Cite journal|url=https://adsabs.harvard.edu/full/1906ApJ....24..309E |journal=Astrophysical Journal |volume=24 |page=309 |date=1906 |first1=G. |last1=Eberhard |title=A Spectroscopic Investigation of Dr. G. Urbain's Preparations of Terbium |issue=5|doi=10.1086/141398 |bibcode=1906ApJ....24..309E }}{{Cite journal |last1=Stubblefield |first1=C. T. |last2=Eick |first2=H. |last3=Eyring |first3=L. |date=August 1956 |title=Terbium Oxides. II. The Heats of Formation of Several Oxides 1 |url=https://pubs.acs.org/doi/abs/10.1021/ja01597a005 |journal=Journal of the American Chemical Society |language=en |volume=78 |issue=16 |pages=3877–3879 |doi=10.1021/ja01597a005 |bibcode=1956JAChS..78.3877S |issn=0002-7863|url-access=subscription }} and soluble oxides after combustion were noted to be colorless.{{Cite book |last=Watts |first=Henry |url=https://books.google.com/books?id=sYEPAQAAIAAJ&dq=terbium+sulfates+discovery&pg=PA2155 |title=A Dictionary of Chemistry and the Allied Branches of Other Sciences |date=1881 |publisher=Longmans, Green, and Company |pages=2155 |language=en}} Until the advent of spectral analysis, arguments went back and forth as to whether erbia even existed. Spectral analysis by Marc Delafontaine allowed the separate elements and their oxides to be identified, but in his publications, the names of erbium and terbium were switched,{{Sfn|Voncken|2016|p=10-11}} following a brief period where terbium was renamed "mosandrum", after Mosander.{{Cite journal |last=Holden |first=Norman E. |date=March 12, 2004 |orig-date=July 8th, 2001 |title=History of the Origin of the Chemical Elements and Their Discoverers |url=https://www.nndc.bnl.gov/content/elements.html |journal=41st IUPAC General Assembly in Brisbane, Australia}} The names have remained switched ever since.

The early years of preparing terbium (as terbium oxide) were difficult. Metal oxides from gadolinite and samarskite were dissolved in nitric acid, and the solution was further separated using oxalic acid and potassium sulfate. There was great difficulty in separating erbia from terbia; in 1881, it was noted that there was no satisfactory method to separate the two. By 1914, different solvents had been used to separate terbium from its host minerals, but the process of separating terbium from its neighbor elements - gadolinium and dysprosium - was described as "tedious" but possible.{{Cite journal |last1=James |first1=C. |url=https://books.google.com/books?id=Yf_yAAAAMAAJ |journal=Journal of the American Chemical Society |last2=Bissel |first2=D. W. |date=June 4, 1914 |publisher=American Chemical Society |pages=2062 |language=en |title=Terbium}} Modern terbium extraction methods are based on the liquid–liquid extraction process developed by Werner Fischer et al., in 1937.{{Cite book |last1=Bünzli |first1=Jean-Claude G. |url=https://onlinelibrary.wiley.com/doi/book/10.1002/14356007 |title=Ullmann's Encyclopedia of Industrial Chemistry |last2=Mcgill |first2=Ian |date=2003-03-11 |publisher=Wiley |isbn=978-3-527-30385-4 |edition=1 |language=en |chapter=Rare Earth Elements |doi=10.1002/14356007.a22_607.pub2}}

Image:Xenotim mineralogisches museum bonn.jpg

Terbium occurs with other rare earth elements in many minerals, including monazite ({{chem2|(Ce,La,Th,Nd,Y)PO4}} with up to 0.03% terbium), xenotime ({{chem2|YPO4}}) and euxenite ({{chem2|(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.{{cite book | last =Patnaik | first =Pradyot | date = 2003 | title =Handbook of Inorganic Chemical Compounds | publisher = McGraw-Hill | pages = 920–921| isbn =978-0-07-049439-8 | url= https://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA243 | access-date = 2009-06-06}} No terbium-dominant mineral has yet been found.{{Cite journal |last=Attia |first=Yosry A. |date=October 1990 |title=Extraction and Refining of High Purity Terbium Metal From Rare Earth Resources |url=http://www.tandfonline.com/doi/abs/10.1080/08827509008952668 |journal=Mineral Processing and Extractive Metallurgy Review |language=en |volume=7 |issue=2 |pages=95–114 |doi=10.1080/08827509008952668 |bibcode=1990MPEMR...7...95A |issn=0882-7508|url-access=subscription }}

Terbium (as the species Tb II) has been detected in the atmosphere of KELT-9b, a hot-Jupiter planet outside the Solar System.{{Cite journal |last1=Borsato |first1=N. W. |last2=Hoeijmakers |first2=H. J. |last3=Prinoth |first3=B. |last4=Thorsbro |first4=B. |last5=Forsberg |first5=R. |last6=Kitzmann |first6=D. |last7=Jones |first7=K. |last8=Heng |first8=K. |date=May 2023 |title=The Mantis Network: III. Expanding the limits of chemical searches within ultra-hot Jupiters: New detections of Ca I, V I, Ti I, Cr I, Ni I, Sr II, Ba II, and Tb II in KELT-9 b |url=https://www.aanda.org/10.1051/0004-6361/202245121 |journal=Astronomy & Astrophysics |volume=673 |pages=A158 |arxiv=2304.04285 |doi=10.1051/0004-6361/202245121 |bibcode=2023A&A...673A.158B |issn=0004-6361}}

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.

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".{{cite journal | last1=Takaya | first1=Yutaro | last2=Yasukawa | first2=Kazutaka | last3=Kawasaki | first3=Takehiro | display-authors=etal | title=The tremendous potential of deep-sea mud as a source of rare-earth elements | journal=Scientific Reports | volume=8 | issue=1 | date=2018-04-10 | issn=2045-2322 | doi=10.1038/s41598-018-23948-5 | page=5763| pmid=29636486 | pmc=5893572 | bibcode=2018NatSR...8.5763T }}

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. 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 {{chem2|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 agents. 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 2020, the annual demand for terbium was estimated at {{Convert|340|t|lb}}.{{Cite journal |last1=Gao |first1=Cuixia |last2=Xu |first2=Yufei |last3=Geng |first3=Yong |last4=Xiao |first4=Shijiang |date=2022-12-01 |title=Uncovering terbium metabolism in China: A dynamic material flow analysis |url=https://linkinghub.elsevier.com/retrieve/pii/S0301420722004603 |journal=Resources Policy |volume=79 |pages=103017 |doi=10.1016/j.resourpol.2022.103017 |bibcode=2022RePol..7903017G |issn=0301-4207|url-access=subscription }} Terbium is not distinguished from other rare earths in the United States Geological Survey's Mineral Commodity Summaries, which in 2024 estimated the global reserves of rare earth minerals at {{Convert|110000000|t|lb}}.{{Cite journal |date=January 2024 |title=Rare Earths |url=https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-rare-earths.pdf |journal=Mineral Commodity Summaries |pages=144–145 |via=U. S. Geological Survey}}

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 zirconium dioxide ({{chem2|ZrO2}}).{{cite book | editor = Lide, D. R. | title = CRC Handbook of Chemistry and Physics | edition = 86th | location = Boca Raton (FL) | publisher = CRC Press | year = 2005 | isbn = 978-0-8493-0486-6 |author=Hammond, C. R. |chapter=The Elements}}{{Sfn|Voncken|2016|p=101}}

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, and other magnetomechanical devices. Terfenol-D is a terbium alloy that expands or contracts in the presence of a magnetic field.{{Cite journal |last=Deng |first=Geng |date=January 2018 |title=Terbium glows green |url=https://www.nature.com/articles/nchem.2914 |journal=Nature Chemistry |language=en |volume=10 |issue=1 |pages=110 |doi=10.1038/nchem.2914 |pmid=29256517 |bibcode=2018NatCh..10..110D |issn=1755-4349}} It has the highest magnetostriction of any alloy.{{cite journal|doi=10.1016/j.sna.2008.11.026|title=New elastomer–Terfenol-D magnetostrictive composites|date=2009|author=Rodriguez, C|journal=Sensors and Actuators A: Physical|volume=149|page=251|last2=Rodriguez|first2=M.|last3=Orue|first3=I.|last4=Vilas|first4=J.|last5=Barandiaran|first5=J.|last6=Gubieda|first6=M.|last7=Leon|first7=L.|issue=2|bibcode=2009SeAcA.149..251R }} It is used to increase verdet constant in long-distance fiber optic communication.{{cite web |url=https://www.stanfordmaterials.com/blog/terbium-uses-in-electronics.html |title=Terbium Uses in Electronics |last=Loewen |first=Eric |website=Stanford Advanced Materials |access-date=Aug 25, 2024}}{{cite journal |last1=Sun |first1=L. |last2=Jiang |first2=S. |year=2010 |title=Compact all-fiber optical Faraday components using 65-wt%-terbium–doped fiber with a record Verdet constant of −32 rad/(Tm) |journal=Optics Express |volume=18 |issue=12 |pages=12191–12196 |doi=10.1364/OE.18.012191|pmid=20588343 |bibcode=2010OExpr..1812191S }} Terbium-doped garnets are also used in optical isolators, which prevents reflected light from traveling back along the optical fiber.{{cite journal |last1=Geho |first1=Mikio |last2=Takagi |first2=Takashi |year=2005 |title=Development of Optical Isolators for Visible Light Using Terbium Aluminum Garnet (Tb₃Al₅O₁₂) Single Crystals |journal=Japanese Journal of Applied Physics |volume=44 |issue=7R |page=4967 |doi=10.1143/JJAP.44.4967|bibcode=2005JaJAP..44.4967G }}

Terbium oxides are used in green phosphors in fluorescent lamps, color TV tubes, and flat screen monitors.{{Sfn|Voncken|2016|p=100}} Terbium, along with all other lanthanides except lanthanum and lutetium, is luminescent in the 3+ oxidation state.{{Cite book |last1=Hänninen |first1=Pekka |url=https://books.google.com/books?id=SWxwcXO94M8C |title=Lanthanide Luminescence: Photophysical, Analytical and Biological Aspects |last2=Härmä |first2=Harri |date=2011-06-21 |publisher=Springer Science & Business Media |isbn=978-3-642-21023-5 |pages=15–20 |language=en}} 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 trichromatic lighting, 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.

In 2023, terbium compounds were used to create a lattice with a single iron atom that was then examined by synchrotron x-ray beam. This was the first successful attempt to characterize a single atom at sub-atomic levels.{{Cite journal |last1=Ajayi |first1=Tolulope M. |last2=Shirato |first2=Nozomi |last3=Rojas |first3=Tomas |last4=Wieghold |first4=Sarah |last5=Cheng |first5=Xinyue |last6=Latt |first6=Kyaw Zin |last7=Trainer |first7=Daniel J. |last8=Dandu |first8=Naveen K. |last9=Li |first9=Yiming |last10=Premarathna |first10=Sineth |last11=Sarkar |first11=Sanjoy |last12=Rosenmann |first12=Daniel |last13=Liu |first13=Yuzi |last14=Kyritsakas |first14=Nathalie |last15=Wang |first15=Shaoze |date=June 2023 |title=Characterization of just one atom using synchrotron X-rays |url=https://www.nature.com/articles/s41586-023-06011-w |journal=Nature |language=en |volume=618 |issue=7963 |pages=69–73 |doi=10.1038/s41586-023-06011-w |pmid=37259001 |bibcode=2023Natur.618...69A |osti=2001465 |s2cid=258992110 |issn=1476-4687}}

Terbium, along with many of the other rare earth elements, is poorly studied in terms of its toxicology and environmental impacts. Few health-based guidance values for safe exposure to terbium are available.{{Cite journal |last1=Kowalczyk |first1=Ewelina |last2=Givelet |first2=Lucas |last3=Amlund |first3=Heidi |last4=Sloth |first4=Jens Jørgen |last5=Hansen |first5=Max |date=May 2022 |title=Risk assessment of rare earth elements, antimony, barium, boron, lithium, tellurium, thallium and vanadium in teas |journal=EFSA Journal |volume=20 |issue=Suppl 1 |pages=e200410 |doi=10.2903/j.efsa.2022.e200410 |pmc=9131585 |pmid=35634564}} No values are established in the United States by the Occupational Safety and Health Administration or American Conference of Governmental Industrial Hygienists at which terbium exposure becomes hazardous, and it is not considered a hazardous substance under the Globally Harmonized System of Classification and Labelling of Chemicals.{{Cite web |date=January 26, 2016 |title=Terbium Safety Data Sheet |url=https://www.ameslab.gov/sites/default/files/inline-files/65_Terbium_SDS.pdf |access-date=August 25, 2024 |website=Ames Laboratory, U. S. Department of Energy}}

Reviews of the toxicity of the rare earth elements place terbium and its compounds as "of low to moderately toxicity", remarking on the lack of detailed studies on their hazards{{Cite journal |last1=Rim |first1=Kyung Taek |last2=Koo |first2=Kwon Ho |last3=Park |first3=Jung Sun |date=March 2013 |title=Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review |journal=Safety and Health at Work |language=en |volume=4 |issue=1 |pages=12–26 |doi=10.5491/SHAW.2013.4.1.12 |pmc=3601293 |pmid=23516020}} and the lack of market demand forestalling evidence of toxicity.{{Cite journal |last1=Chen |first1=Haibin |last2=Chen |first2=Zhibiao |last3=Chen |first3=Zhiqiang |last4=Ou |first4=Xiaolin |last5=Chen |first5=Junjia |date=May 2020 |title=Calculation of Toxicity Coefficient of Potential Ecological Risk Assessment of Rare Earth Elements |url=https://link.springer.com/10.1007/s00128-020-02840-x |journal=Bulletin of Environmental Contamination and Toxicology |language=en |volume=104 |issue=5 |pages=582–587 |doi=10.1007/s00128-020-02840-x |pmid=32296855 |bibcode=2020BuECT.104..582C |issn=0007-4861|url-access=subscription }}

Some studies demonstrate environmental accumulation of terbium as hazardous to fish and plants.{{Cite journal |last1=Hanana |first1=Houda |last2=Taranu |first2=Zofia E. |last3=Turcotte |first3=Patrice |last4=Gagnon |first4=Christian |last5=Kowalczyk |first5=Joanna |last6=Gagné |first6=François |date=2021-07-10 |title=Sublethal effects of terbium and praseodymium in juvenile rainbow trout |url=https://linkinghub.elsevier.com/retrieve/pii/S0048969721011098 |journal=Science of the Total Environment |volume=777 |pages=146042 |doi=10.1016/j.scitotenv.2021.146042 |bibcode=2021ScTEn.77746042H |issn=0048-9697|url-access=subscription }}{{Cite journal |last1=Sturla Lompré |first1=Julieta |last2=Moleiro |first2=Pedro |last3=De Marchi |first3=Lucia |last4=Soares |first4=Amadeu M. V. M. |last5=Pretti |first5=Carlo |last6=Chielini |first6=Federica |last7=Pereira |first7=Eduarda |last8=Freitas |first8=Rosa |date=2021-08-25 |title=Bioaccumulation and ecotoxicological responses of clams exposed to terbium and carbon nanotubes: Comparison between native (Ruditapes decussatus) and invasive (Ruditapes philippinarum) species |url=https://linkinghub.elsevier.com/retrieve/pii/S0048969721019847 |journal=Science of the Total Environment |volume=784 |pages=146914 |doi=10.1016/j.scitotenv.2021.146914 |pmid=33901954 |bibcode=2021ScTEn.78446914S |issn=0048-9697|url-access=subscription }} High exposures of terbium may enhance the toxicity of other substances causing endocytosis in plant cells.{{Cite journal |last1=Cheng |first1=Mengzhu |last2=Zhou |first2=Qing |last3=Wang |first3=Lihong |last4=Jiao |first4=Yunlong |last5=Liu |first5=Yongqiang |last6=Tan |first6=Li |last7=Zhu |first7=Hong |last8=Nagawa |first8=Shingo |last9=Wei |first9=Haiyan |last10=Yang |first10=Zhenbiao |last11=Yang |first11=Qing |last12=Huang |first12=Xiaohua |date=2022-01-05 |title=A new mechanism by which environmental hazardous substances enhance their toxicities to plants |url=https://linkinghub.elsevier.com/retrieve/pii/S0304389421017696 |journal=Journal of Hazardous Materials |volume=421 |pages=126802 |doi=10.1016/j.jhazmat.2021.126802 |pmid=34396977 |bibcode=2022JHzM..42126802C |issn=0304-3894|url-access=subscription }}

• Terbium compounds
• List of elements facing shortage

{{Reflist}}

• {{Cite book |last=Voncken |first=J.H.L. |title=The Rare Earth Elements: An Introduction |series=SpringerBriefs in Earth Sciences |publisher=Cham : Springer International Publishing |year=2016 |isbn=978-3-319-26809-5 |edition=1st |language=en |doi=10.1007/978-3-319-26809-5}}

{{Commons|Terbium}}

{{wiktionary|terbium}}

• [http://www.webelements.com/webelements/elements/text/Tb/index.html WebElements.com – Terbium]
• [http://education.jlab.org/itselemental/ele065.html It's Elemental – Terbium]

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