View source for Samarium

{{Use American English|date=December 2022}}
{{Infobox samarium}}
'''Samarium''' is a [[chemical element]]; it has [[chemical symbol|symbol]] '''Sm''' and [[atomic number]] 62. It is a moderately hard silvery [[metal]] that slowly oxidizes in air. Being a typical member of the [[lanthanide]] series, samarium usually has the [[oxidation state]] +3. Compounds of samarium(II) are also known, most notably the [[monoxide]] SmO, [[samarium monochalcogenides|monochalcogenides]] SmS, SmSe and SmTe, as well as [[samarium(II) iodide]].

Discovered in 1879 by French chemist [[Paul-Émile Lecoq de Boisbaudran]], samarium was named after the mineral [[samarskite]] from which it was isolated. The mineral itself was named after a Russian mine official, Colonel [[Vassili Samarsky-Bykhovets]], who thus became the first person to have a chemical element named after him, though the name was indirect.

Samarium occurs in concentration up to 2.8% in several minerals including [[cerite]], [[gadolinite]], samarskite, [[monazite]] and [[bastnäsite]], the last two being the most common commercial sources of the element. These minerals are mostly found in China, the United States, Brazil, India, Sri Lanka and Australia; China is by far the world leader in samarium mining and production.

The main commercial use of samarium is in [[samarium–cobalt magnet]]s, which have permanent [[magnet]]ization second only to [[neodymium magnet]]s; however, samarium compounds can withstand significantly higher temperatures, above {{convert|700|C|F}}, without losing their permanent magnetic properties. The [[radioisotope]] samarium-153 is the active component of the drug [[samarium (153Sm) lexidronam|samarium (<sup>153</sup>Sm) lexidronam]] (Quadramet), which kills cancer cells in [[lung cancer]], [[prostate cancer]], [[breast cancer]] and [[osteosarcoma]]. Another isotope, [[samarium-149]], is a strong [[neutron]] absorber and so is added to [[control rod]]s of [[nuclear reactor]]s. It also forms as a decay product during the reactor operation and is one of the important factors considered in the reactor design and operation. Other uses of samarium include [[catalysis]] of [[chemical reaction]]s, [[samarium–neodymium dating|radioactive dating]] and [[X-ray laser]]s. Samarium(II) iodide, in particular, is a common [[reducing agent]] in [[chemical synthesis]].

Samarium has no biological role; some samarium salts are slightly toxic.<ref name=emsley />

==Physical properties==
Samarium is a [[rare earth element]] with a hardness and density similar to [[zinc]]. With a boiling point of {{convert|1794|C|F}}, samarium is the third most [[Volatility (chemistry)|volatile]] lanthanide after [[ytterbium]] and [[europium]] and comparable in this respect to [[lead]] and [[barium]]; this helps separation of samarium from its ores.<ref name="Lange">{{cite book|editor=J.A. Dean|title=Lange's Handbook of Chemistry|edition=15th|publisher=McGraw-Hill|location=New York, NY|year=1999|at=Section 3; Table 3.2 Physical Constants of Inorganic Compounds|isbn= 978-0-07016384-3}}</ref><ref name="CRC" /> When freshly prepared, samarium has a silvery [[Lustre (mineralogy)|lustre]], and takes on a duller appearance when oxidized in air. Samarium is calculated to have one of the largest [[atomic radius|atomic radii]] of the elements; with a radius of 238&nbsp;pm, only [[potassium]], [[praseodymium]], [[barium]], [[rubidium]] and [[caesium]] are larger.<ref>{{cite journal |last1=Clementi |first1=E. |last2=Raimond |first2=D. L. |last3=Reinhardt |first3=W. P. |year=1967 |title=Atomic Screening Constants from SCF Functions. II. Atoms with 37 to 86 Electrons |journal=[[Journal of Chemical Physics]] |volume=47 |issue=4 |pages=1300–1307 |bibcode=1967JChPh..47.1300C |doi=10.1063/1.1712084}}</ref>

In ambient conditions, samarium has a [[rhombohedral]] structure (α form). Upon heating to {{convert|731|C|F}}, its crystal symmetry changes to [[Hexagonal crystal system|hexagonal close-packed]] (''hcp''),; it has  actual transition temperature depending on metal purity. Further heating to {{convert|922|C|F}} transforms the metal into a [[Cubic crystal system|body-centered cubic]] (''bcc'') phase. Heating to {{convert|300|C|F}} plus compression to 40&nbsp;[[bar (unit)|kbar]] results in a double-hexagonally close-packed structure (''dhcp''). Higher pressure of the order of hundreds or thousands of kilobars induces a series of phase transformations, in particular with a [[tetragonal crystal system|tetragonal]] phase appearing at about 900&nbsp;kbar.<ref name="sm" /> In one study, the ''dhcp'' phase could be produced without compression, using a nonequilibrium annealing regime with a rapid temperature change between about {{convert|400|C|F}} and {{convert|700|C|F}}, confirming the transient character of this samarium phase. Thin films of samarium obtained by vapor deposition may contain the ''hcp'' or ''dhcp'' phases in ambient conditions.<ref name="sm">{{cite journal|doi=10.1016/0022-5088(85)90294-2|last1=Shi|first1=N.|date=1985|page=21|volume=113|journal=Journal of the Less Common Metals|last2=Fort|first2=D.|title=Preparation of samarium in the double hexagonal close packed form|issue=2}}</ref>

Samarium and its [[sesquioxide]] are [[paramagnetism|paramagnetic]] at room temperature. Their corresponding effective magnetic moments, below 2 [[bohr magneton]]s, are the third-lowest among lanthanides (and their oxides) after lanthanum and lutetium. The metal transforms to an [[antiferromagnetism|antiferromagnetic]] state upon cooling to 14.8&nbsp;K.<ref>{{cite journal |last1=Lock |first1=J. M. |title=The Magnetic Susceptibilities of Lanthanum, Cerium, Praseodymium, Neodymium and Samarium, from 1.5 K to 300 K |journal=Proceedings of the Physical Society |series=Series B |volume=70 |page=566 |date=1957 |doi=10.1088/0370-1301/70/6/304 |issue=6 |bibcode=1957PPSB...70..566L}}</ref><ref>{{cite journal |last1=Huray |first1=P. |last2=Nave |first2=S. |last3=Haire |first3=R. |title=Magnetism of the heavy 5f elements |journal=Journal of the Less Common Metals |volume=93 |page=293 |date=1983 |doi=10.1016/0022-5088(83)90175-3 |issue=2}}</ref> Individual samarium atoms can be isolated by encapsulating them into [[fullerene]] molecules.<ref>{{cite journal |doi=10.1016/S0921-4526(02)00991-2 |title=Electronic and geometric structures of metallofullerene peapods |date=2002 |last1=Okazaki |first1=T. |journal=Physica B |volume=323 |issue=1–4 |page=97 |bibcode=2002PhyB..323...97O |last2=Suenaga |first2=Kazutomo |last3=Hirahara |first3=Kaori |last4=Bandow |first4=Shunji |last5=Iijima |first5=Sumio |last6=Shinohara |first6=Hisanori |display-authors=3}}</ref> They can also be intercalated into the interstices of the bulk C<sub>60</sub> to form a solid solution of nominal composition Sm<sub>3</sub>C<sub>60</sub>, which is [[superconductivity|superconductive]] at a temperature of 8&nbsp;K.<ref>{{cite journal |last1=Chen |first1=X. |last2=Roth |first2=G. |title=Superconductivity at 8 K in samarium-doped C60 |journal=Physical Review B |volume=52 |date=1995 |doi=10.1103/PhysRevB.52.15534 |pmid=9980911 |issue=21 |pages=15534–15536 |bibcode=1995PhRvB..5215534C}}</ref> Samarium doping of [[iron-based superconductor]]s – a class of [[high-temperature superconductor]] – increases their transition to normal conductivity temperature up to 56&nbsp;K, the highest value achieved so far in this series.<ref name="Wu2008">{{cite journal |arxiv=0811.0761 |title=Superconductivity at 56 K in Samarium-doped SrFeAsF |last1=Wu |first1=G. |date=2008 |doi=10.1088/0953-8984/21/14/142203 |pmid=21825317 |journal=Journal of Physics: Condensed Matter |volume=21 |issue=14 |page=142203|bibcode=2009JPCM...21n2203W |last2=Xie |first2=Y. L. |last3=Chen |first3=H. |last4=Zhong |first4=M. |last5=Liu |first5=R. H. |last6=Shi |first6=B. C. |last7=Li |first7=Q. J. |last8=Wang |first8=X. F. |last9=Wu |first9=T. |s2cid=41728130 |display-authors=3}}</ref>

== Chemical properties ==

In air, samarium slowly oxidizes at room temperature and spontaneously ignites at {{convert|150|C|F}}.<ref name="emsley" /><ref name="CRC" /> Even when stored under [[mineral oil]], samarium gradually oxidizes and develops a grayish-yellow powder of the [[oxide]]-[[hydroxide]] mixture at the surface. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as [[argon]].

Samarium is quite electropositive and reacts slowly with cold water and rapidly with hot water to form samarium hydroxide:<ref name="we" />
: {{chem2|2Sm_{(s)} + 6H2O_{(l)} → 2Sm(OH)3_{(aq)} + 3H2_{(g)}|}}

Samarium dissolves readily in dilute [[sulfuric acid]] to form solutions containing the yellow<ref name="g1243">[[#Greenwood|Greenwood]], p. 1243</ref> to pale green Sm(III) ions, which exist as {{chem2|[Sm(OH2)9](3+)|}} complexes:<ref name="we">{{cite web| url =https://www.webelements.com/samarium/chemistry.html| title =Chemical reactions of Samarium| publisher=Webelements| access-date=2009-06-06}}</ref>

: {{chem2|2Sm_{(s)} + 3H2SO4_{(aq)} → 2Sm(3+)_{(aq)} + 3SO4(2-)_{(aq)} + 3H2_{(g)}|}}

Samarium is one of the few lanthanides with a relatively accessible +2 oxidation state, alongside Eu and Yb.<ref>{{Cite book |title=The lanthanides and actinides: synthesis, reactivity, properties and applications |date=2022 |editor=Stephen T. Liddle |editor2=David P. Mills |editor3=Louise S. Natrajan |isbn=978-1-80061-015-6 |location=London |oclc=1251740566 |page=213}}</ref> {{chem2|Sm(2+)}} ions are blood-red in aqueous solution.<ref name="g1248">[[#Greenwood|Greenwood]], p. 1248</ref>

==Compounds==
{{Main article|Samarium compounds}}

{| class="wikitable" style="text-align: center; font-size: 90%;"
|-
! Formula
! color
! symmetry
! [[space group]]
! No
! [[Pearson symbol]]
! ''a'' (pm)
! ''b'' (pm)
! ''c'' (pm)
! ''Z''
! density, <br/>g/cm<sup>3</sup>
|-
| Sm
| silvery
| trigonal<ref name="sm"/>
| R{{overline|3}}m
| 166
| hR9
| 362.9
| 362.9
| 2621.3
| 9
| 7.52
|-
| Sm
| silvery
| hexagonal<ref name="sm" />
| P6<sub>3</sub>/mmc
| 194
| hP4
| 362
| 362
| 1168
| 4
| 7.54
|-
| Sm
| silvery
| tetragonal<ref name="sm2">{{cite journal |doi=10.1016/0375-9601(91)90346-A |date=1991|page=89 |volume=158 |issue=1–2 |journal=Physics Letters A |title=A new ultra-high pressure phase in samarium |bibcode=1991PhLA..158...89V |last1=Vohra |first1=Y. |last2=Akella |first2=Jagannadham |last3=Weir |first3=Sam |last4=Smith |first4=Gordon S. |url=https://zenodo.org/record/1258493}}</ref>
| I4/mmm
| 139
| tI2
| 240.2
| 240.2
| 423.1
| 2
| 20.46
|-
| SmO
| golden
| cubic<ref name="smox">{{cite journal|last1=Leger|first1=J.|last2=Yacoubi|first2=N.|last3=Loriers|first3=J. |title=Synthesis of rare earth monoxides |journal=Journal of Solid State Chemistry |volume=36 |page=261 |date=1981 |doi=10.1016/0022-4596(81)90436-9 |issue=3 |bibcode=1981JSSCh..36..261L |doi-access=}}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 494.3
| 494.3
| 494.3
| 4
| 9.15
|-
| Sm<sub>2</sub>O<sub>3</sub>
|
| trigonal<ref name="smo">{{cite journal|doi=10.1016/0022-4596(81)90058-X|last1=Gouteron|date=1981|first1=J.|page=288|volume=38|journal=Journal of Solid State Chemistry|title=Raman spectra of lanthanide sesquioxide single crystals: Correlation between A and B-type structures|issue=3|bibcode=1981JSSCh..38..288G|last2=Michel|first2=D.|last3=Lejus|first3=A. M.|last4=Zarembowitch|first4=J. }}</ref>
| P{{overline|3}}m1
| 164
| hP5
| 377.8
| 377.8
| 594
| 1
| 7.89
|-
| Sm<sub>2</sub>O<sub>3</sub>
|
| monoclinic<ref name="smo" />
| C2/m
| 12
| mS30
| 1418
| 362.4
| 885.5
| 6
| 7.76
|-
| Sm<sub>2</sub>O<sub>3</sub>
|
| cubic<ref name="smo2">{{cite journal |journal=British Ceramic Transactions and Journal|date=1984|volume=83|issue=4|pages=92–98|last=Taylor |first=D. |title=Thermal Expansion Data: III Sesquioxides, M<sub>2</sub>O<sub>3</sub>, with the corundum and the A-, B- and C-M<sub>2</sub>O<sub>3</sub> structures}}</ref>
| Ia{{overline|3}}
| 206
| cI80
| 1093
| 1093
| 1093
| 16
| 7.1
|-
| SmH<sub>2</sub>
|
| cubic<ref name="smh2">{{cite journal|last1=Daou|first1=J.|last2=Vajda|first2=P.|last3=Burger|first3=J.|title=Low temperature thermal expansion in SmH2+x|journal=Solid State Communications|volume=71|page=1145|date=1989|doi=10.1016/0038-1098(89)90728-X|issue=12|bibcode=1989SSCom..71.1145D }}</ref>
| Fm{{overline|3}}m
| 225
| cF12
| 537.73
| 537.73
| 537.73
| 4
| 6.51
|-
| SmH<sub>3</sub>
|
| hexagonal<ref name="smh3">{{cite journal|doi=10.1016/S0925-8388(96)03071-X|last1=Dolukhanyan|date=1997|first1=S.|page=10|volume=253–254|journal=Journal of Alloys and Compounds|title=Synthesis of novel compounds by hydrogen combustion}}</ref>
| P{{overline|3}}c1
| 165
| hP24
| 377.1
| 377.1
| 667.2
| 6
|
|-
| Sm<sub>2</sub>B<sub>5</sub>
| gray
| monoclinic<ref>{{cite journal|doi=10.1007/BF00795346|last1=Zavalii|date=1990|first1=L. V.|page=471|volume=29|journal=Soviet Powder Metallurgy and Metal Ceramics|last2=Kuz'ma|first2=Yu. B.|last3=Mikhalenko|first3=S. I.|title=Sm2B5 boride and its structure|issue=6|s2cid=138416728}}</ref>
| P2<sub>1</sub>/c
| 14
| mP28
| 717.9
| 718
| 720.5
| 4
| 6.49
|-
| SmB<sub>2</sub>
|
| hexagonal<ref name="smb2">{{cite journal|doi=10.1016/0022-5088(77)90221-1|last1=Cannon|date=1977|first1=J.|page=83|volume=56|journal=Journal of the Less Common Metals|last2=Cannon|first2=D.|last3=Tracyhall|first3=H.|title=High pressure syntheses of SmB2 and GdB12}}</ref>
| P6/mmm
| 191
| hP3
| 331
| 331
| 401.9
| 1
| 7.49
|-
| SmB<sub>4</sub>
|
| tetragonal<ref>{{cite journal|last1=Etourneau|doi=10.1016/0022-5088(79)90038-9|first1=J.|date=1979|page=531|volume=67|last2=Mercurio|journal=Journal of the Less Common Metals |first2=J. |last3=Berrada |first3=A. |last4=Hagenmuller |first4=P. |last5=Georges |first5=R. |last6=Bourezg |first6=R. |last7=Gianduzzo |first7=J.|title=The magnetic and electrical properties of some rare earth tetraborides|issue=2}}</ref>
| P4/mbm
| 127
| tP20
| 717.9
| 717.9
| 406.7
| 4
| 6.14
|-
| SmB<sub>6</sub>
|
| cubic<ref name="smb6">{{cite journal|doi=10.1111/j.1151-2916.1972.tb11344.x|last1=Solovyev|first1=G. I.|date=1972|page=475|volume=55|journal=Journal of the American Ceramic Society|last2=Spear|first2=K. E.|title=Phase Behavior in the Sm-B System|issue=9}}</ref>
| Pm{{overline|3}}m
| 221
| cP7
| 413.4
| 413.4
| 413.4
| 1
| 5.06
|-
| SmB<sub>66</sub>
|
| cubic<ref>{{cite journal|last1=Schwetz|first1=K.|last2=Ettmayer|first2=P.|last3=Kieffer|first3=R.|last4=Lipp|first4=A.|title=Über die Hektoboridphasen der Lanthaniden und Aktiniden|journal=Journal of the Less Common Metals|volume=26|page=99|date=1972|doi=10.1016/0022-5088(72)90012-4}}</ref>
| Fm{{overline|3}}c
| 226
| cF1936
| 2348.7
| 2348.7
| 2348.7
| 24
| 2.66
|-
| Sm<sub>2</sub>C<sub>3</sub>
|
| cubic<ref name="smc" />
| I{{overline|4}}3d
| 220
| cI40
| 839.89
| 839.89
| 839.89
| 8
| 7.55
|-
| SmC<sub>2</sub>
|
| tetragonal<ref name="smc">{{cite journal|doi=10.1021/ja01550a017|last1=Spedding|date=1958|first1=F. H.|page=4499|volume=80|journal=Journal of the American Chemical Society|last2=Gschneidner|first2=K.|last3=Daane|first3=A. H.|title=The Crystal Structures of Some of the Rare Earth Carbides|issue=17|bibcode=1958JAChS..80.4499S }}</ref>
| I4/mmm
| 139
| tI6
| 377
| 377
| 633.1
| 2
| 6.44
|-
| SmF<sub>2</sub>
| purple<ref name="g1241" />
| cubic<ref name="smf2">{{cite journal|last1=Greis|first1=O.|title=Über neue Verbindungen im system SmF2_SmF3|journal=Journal of Solid State Chemistry|volume=24|page=227|date=1978|doi=10.1016/0022-4596(78)90013-0|issue=2|bibcode=1978JSSCh..24..227G }}</ref>
| Fm{{overline|3}}m
| 225
| cF12
| 587.1
| 587.1
| 587.1
| 4
| 6.18
|-
| SmF<sub>3</sub>
| white<ref name="g1241" />
| orthorhombic<ref name="smf2" />
| Pnma
| 62
| oP16
| 667.22
| 705.85
| 440.43
| 4
| 6.64
|-
| SmCl<sub>2</sub>
| brown<ref name="g1241" />
| orthorhombic<ref name="smcl2">{{cite journal|doi=10.1016/0022-5088(86)90228-6|last1=Meyer|first1=G.|date=1986|page=187|volume=116|journal=Journal of the Less Common Metals|last2=Schleid|first2=T.|title=The metallothermic reduction of several rare-earth trichlorides with lithium and sodium}}</ref>
| Pnma
| 62
| oP12
| 756.28
| 450.77
| 901.09
| 4
| 4.79
|-
| SmCl<sub>3</sub>
| yellow<ref name="g1241" />
| hexagonal<ref name="smf2" />
| P6<sub>3</sub>/m
| 176
| hP8
| 737.33
| 737.33
| 416.84
| 2
| 4.35
|-
| SmBr<sub>2</sub>
| brown<ref name="g1241" />
| orthorhombic<ref name="smbr2">{{cite journal |journal=Revue de chimie minérale.|title=Revue für anorganic Chemie|date=1973|volume=10|pages=77–92|author=Bärnighausen, H.}}</ref>
| Pnma
| 62
| oP12
| 797.7
| 475.4
| 950.6
| 4
| 5.72
|-
| SmBr<sub>3</sub>
| yellow<ref name="g1241" />
| orthorhombic<ref name="smbr3">{{cite journal|last1=Zachariasen|first1=W. H.|title=Crystal chemical studies of the 5f-series of elements. I. New structure types|journal=Acta Crystallographica|volume=1|page=265|date=1948|doi=10.1107/S0365110X48000703|issue=5|doi-access=|bibcode=1948AcCry...1..265Z }}</ref>
| Cmcm
| 63
| oS16
| 404
| 1265
| 908
| 2
| 5.58
|-
| SmI<sub>2</sub>
| green<ref name="g1241">[[#Greenwood|Greenwood]], p. 1241</ref>
| monoclinic
| P2<sub>1</sub>/c
| 14
| mP12
|
|
|
|
|
|-
| SmI<sub>3</sub>
| orange<ref name="g1241" />
| trigonal<ref name="smI3">{{cite journal|title=Preparation and Crystal Data for Lanthanide and Actinide Triiodides|last1=Asprey|first1=L. B.|last2=Keenan|first2=T. K.|last3=Kruse|first3=F. H.|journal=Inorganic Chemistry|volume=3|page=1137|date=1964|doi=10.1021/ic50018a015|issue=8|url=https://digital.library.unt.edu/ark:/67531/metadc867868/m2/1/high_res_d/4067674.pdf}}</ref>
| R{{overline|3}}
| 63
| hR24
| 749
| 749
| 2080
| 6
| 5.24
|-
| SmN
|
| cubic<ref name="smn">{{cite journal|last1=Brown|first1=R.|title=Composition limits and vaporization behaviour of rare earth nitrides|journal=Journal of Inorganic and Nuclear Chemistry|volume=36|page=2507|date=1974 |doi=10.1016/0022-1902(74)80462-8|issue=11|last2=Clark|first2=N. J.}}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 357
| 357
| 357
| 4
| 8.48
|-
| SmP
|
| cubic<ref name="smp">{{cite journal|last1=Meng|first1=J.|title=Studies on the electrical properties of rare earth monophosphides|journal=Journal of Solid State Chemistry|volume=95|page=346|date=1991 |doi=10.1016/0022-4596(91)90115-X|issue=2|bibcode=1991JSSCh..95..346M|last2=Ren|first2=Yufang }}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 576
| 576
| 576
| 4
| 6.3
|-
| SmAs
|
| cubic<ref name="smas">{{cite journal|last1=Beeken|first1=R.|last2=Schweitzer|first2=J.|title=Intermediate valence in alloys of SmSe with SmAs|journal=Physical Review B|volume=23|page=3620|date=1981|doi=10.1103/PhysRevB.23.3620|issue=8|bibcode=1981PhRvB..23.3620B }}</ref>
| Fm{{overline|3}}m
| 225
| cF8
| 591.5
| 591.5
| 591.5
| 4
| 7.23
|}

===Oxides===
The most stable oxide of samarium is the [[sesquioxide]] Sm<sub>2</sub>O<sub>3</sub>. Like many samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm<sub>2</sub>O<sub>3</sub> is high (2345&nbsp;°C), so it is usually melted not by direct heating, but with [[induction heating]], through a radio-frequency coil. Sm<sub>2</sub>O<sub>3</sub> crystals of monoclinic symmetry can be grown by the flame fusion method ([[Verneuil process]]) from Sm<sub>2</sub>O<sub>3</sub> powder, that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm<sub>2</sub>O<sub>3</sub> to {{convert|1900|C|F}} converts it to the more stable monoclinic phase.<ref name="smo" /> Cubic Sm<sub>2</sub>O<sub>3</sub> has also been described.<ref name="smo2" />

Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm<sub>2</sub>O<sub>3</sub> with samarium metal at high temperature (1000&nbsp;°C) and a pressure above 50&nbsp;kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure.<ref name="smox" /><ref name="g1239">[[#Greenwood|Greenwood]], p. 1239</ref>

===Chalcogenides===
{{see also|Samarium monochalcogenides}}
Samarium forms a trivalent [[samarium(III) sulfide|sulfide]], [[selenide]] and [[telluride (chemistry)|telluride]]. Divalent chalcogenides SmS, SmSe and SmTe with a cubic rock-salt crystal structure are known. These chalcogenides convert from a semiconducting to metallic state at room temperature upon application of pressure.<ref>{{Cite journal |last1=Bakar |first1=Abu |last2=Afaq |first2=A. |last3=Khan |first3=M. Faizan |last4=ul Aarifeen |first4=Najm |last5=Imran Jamil |first5=M. |last6=Asif |first6=Muhammad |date=2020-01-01 |title=Insight into the structural, vibrational and thermodynamic properties of SmX (X = S, Se, Te) chalcogenides: First-principles investigations |url=https://www.sciencedirect.com/science/article/pii/S0921452619306209 |journal=Physica B: Condensed Matter |language=en |volume=576 |pages=411715 |doi=10.1016/j.physb.2019.411715 |s2cid=204206623 |issn=0921-4526|url-access=subscription }}</ref> Whereas the transition is continuous and occurs at about 20–30&nbsp;kbar in SmSe and SmTe, it is abrupt in SmS and requires only 6.5&nbsp;kbar. This effect results in a spectacular color change in SmS from black to golden yellow when its crystals of films are scratched or polished. The transition does not change the lattice symmetry, but there is a sharp decrease (~15%) in the crystal volume.<ref name="b1">{{Cite book |title=Magnetism: a synchrotron radiation approach |date=2006 |publisher=Springer |first1=E. |last1=Beaurepaire |isbn=978-3-540-33242-8 |location=Berlin |oclc=262692720}}</ref> It exhibits [[hysteresis]], i.e., when the pressure is released, SmS returns to the semiconducting state at a much lower pressure of about 0.4 kbar.<ref name="emsley" /><ref>{{cite journal|last1=Jayaraman|first1=A.|last2=Narayanamurti|first2=V.|last3=Bucher|first3=E.|last4=Maines|first4=R.|title=Continuous and Discontinuous Semiconductor-Metal Transition in Samarium Monochalcogenides Under Pressure|journal=Physical Review Letters|volume=25|page=1430|date=1970|doi=10.1103/PhysRevLett.25.1430|bibcode=1970PhRvL..25.1430J|issue=20}}</ref>

===Halides===

[[File:Samarium(III) chloride hexahydrate.jpg|thumb|right|Samarium trichloride]]

Samarium metal reacts with all the [[halogen]]s, forming trihalides:<ref name="g1236">[[#Greenwood|Greenwood]], pp. 1236, 1241</ref>
:2 Sm (s) + 3 X<sub>2</sub> (g) → 2 SmX<sub>3</sub> (s) (X = F, Cl, Br or I)

Their further reduction with samarium, lithium or sodium metals at elevated temperatures (about 700–900&nbsp;°C) yields the dihalides.<ref name="smcl2" /> The diiodide can also be prepared by heating SmI<sub>3</sub>, or by reacting the metal with [[1,2-Diiodoethane|1,2-diiodoethane]] in anhydrous [[tetrahydrofuran]] at room temperature:<ref name="g1240">[[#Greenwood|Greenwood]], p. 1240</ref>
:Sm (s) + ICH<sub>2</sub>-CH<sub>2</sub>I → SmI<sub>2</sub> + CH<sub>2</sub>=CH<sub>2</sub>.

In addition to dihalides, the reduction also produces many [[Non-stoichiometric compound|non-stoichiometric]] samarium halides with a well-defined crystal structure, such as Sm<sub>3</sub>F<sub>7</sub>, Sm<sub>14</sub>F<sub>33</sub>, Sm<sub>27</sub>F<sub>64</sub>,<ref name="smf2" /> Sm<sub>11</sub>Br<sub>24</sub>, Sm<sub>5</sub>Br<sub>11</sub> and Sm<sub>6</sub>Br<sub>13</sub>.<ref>{{cite journal |last1=Baernighausen |first1=H. |last2=Haschke |first2=John M. |title=Compositions and crystal structures of the intermediate phases in the samarium-bromine system |journal=Inorganic Chemistry |volume=17 |page=18 |date=1978 |doi=10.1021/ic50179a005}}</ref>

Samarium halides change their crystal structures when one type of halide anion is substituted for another, which is an uncommon behavior for most elements (e.g. actinides). Many halides have two major crystal phases for one composition, one being significantly more stable and another being metastable. The latter is formed upon compression or heating, followed by quenching to ambient conditions. For example, compressing the usual monoclinic samarium diiodide and releasing the pressure results in a PbCl<sub>2</sub>-type orthorhombic structure (density 5.90&nbsp;g/cm<sup>3</sup>),<ref>{{cite journal|last1=Beck|first1=H. P.|title=Hochdruckmodifikationen der Diiodide von Sr., Sm und Eu. Eine neue PbCl2-Variante?|journal=Zeitschrift für anorganische und allgemeine Chemie|volume=459|page=81|date=1979|doi=10.1002/zaac.19794590108}}</ref> and similar treatment results in a new phase of samarium triiodide (density 5.97&nbsp;g/cm<sup>3</sup>).<ref>{{cite journal|last1=Beck|first1=H. P.|last2=Gladrow|first2=E.|title=Zur Hochdruckpolymorphie der Seltenerd-Trihalogenide|journal=Zeitschrift für anorganische und allgemeine Chemie|volume=453|page=79|date=1979|doi=10.1002/zaac.19794530610}}</ref>

===Borides===
[[Sintering]] powders of samarium oxide and boron, in a vacuum, yields a powder containing several samarium boride phases; the ratio between these phases can be controlled through the mixing proportion.<ref name="smb6b" /> The powder can be converted into larger crystals of samarium borides using [[Electric arc furnace|arc melting]] or [[zone melting]] techniques, relying on the different melting/crystallization temperature of SmB<sub>6</sub> (2580&nbsp;°C), SmB<sub>4</sub> (about 2300&nbsp;°C) and SmB<sub>66</sub> (2150&nbsp;°C). All these materials are hard, brittle, dark-gray solids with the hardness increasing with the boron content.<ref name="smb6" /> Samarium diboride is too volatile to be produced with these methods and requires high pressure (about 65&nbsp;kbar) and low temperatures between 1140 and 1240&nbsp;°C to stabilize its growth. Increasing the temperature results in the preferential formation of SmB<sub>6</sub>.<ref name="smb2" />

====Samarium hexaboride====
{{Main|Samarium hexaboride}}

Samarium hexaboride is a typical intermediate-valence compound where samarium is present both as Sm<sup>2+</sup> and Sm<sup>3+</sup> ions in a 3:7 ratio.<ref name="smb6b">{{cite journal|last1=Nickerson|first1=J.|last2=White|first2=R.|last3=Lee|first3=K.|last4=Bachmann|first4=R.|last5=Geballe|first5=T.|last6=Hull|first6=G.|title=Physical Properties of SmB<sub>6</sub> |journal=Physical Review B|volume=3|page=2030|date=1971|doi=10.1103/PhysRevB.3.2030|issue=6|bibcode=1971PhRvB...3.2030N }}</ref> It belongs to a class of [[Kondo insulator]]s; at temperatures above 50&nbsp;K, its properties are typical of a Kondo metal, with metallic electrical conductivity characterized by strong electron scattering, whereas at lower temperatures, it behaves as a non-magnetic insulator with a narrow [[band gap]] of about 4–14&nbsp;[[electronvolt|meV]].<ref>{{cite journal |doi=10.1103/PhysRevB.52.R14308 |pmid=9980746 |last1=Nyhus |date=1995 |first1=P. |pages=14308–14311 |volume=52|last2=Cooper|journal=Physical Review B|first2=S.|last3=Fisk|first3=Z.|author4-link=John Sarrao |last4=Sarrao |first4=J. |title=Light scattering from gap excitations and bound states in SmB<sub>6</sub> |issue=20|bibcode=1995PhRvB..5214308N }}</ref> The cooling-induced metal-insulator transition in SmB<sub>6</sub> is accompanied by a sharp increase in the [[thermal conductivity]], peaking at about 15&nbsp;K. The reason for this increase is that electrons themselves do not contribute to the thermal conductivity at low temperatures, which is dominated by [[phonon]]s, but the decrease in electron concentration reduces the rate of electron-phonon scattering.<ref>{{cite journal |last1=Sera |first1=M. |last2=Kobayashi |first2=S. |last3=Hiroi |first3=M.|last4=Kobayashi|first4=N.|last5=Kunii|first5=S.|title=Thermal conductivity of RB<sub>6</sub> (R=Ce, Pr, Nd, Sm, Gd) single crystals |journal=Physical Review B |volume=54 |date=1996 |doi=10.1103/PhysRevB.54.R5207 |pmid=9986570|issue=8 |pages=R5207–R5210|bibcode=1996PhRvB..54.5207S }}</ref>

===Other inorganic compounds===
[[File:Samarium-sulfate.jpg|thumb|upright|alt=A tube of samarium sulfate|Samarium sulfate, Sm<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>]]
Samarium [[carbide]]s are prepared by melting a graphite-metal mixture in an inert atmosphere. After the synthesis, they are unstable in air and need to be studied under an inert atmosphere.<ref name="smc" /> Samarium monophosphide SmP is a [[semiconductor]] with a bandgap of 1.10&nbsp;eV, the same as in [[silicon]], and electrical conductivity of [[N-type semiconductor|n-type]]. It can be prepared by annealing at {{convert|1100|C|F}} an evacuated quartz ampoule containing mixed powders of phosphorus and samarium. Phosphorus is highly volatile at high temperatures and may explode, thus the heating rate has to be kept well below 1&nbsp;°C/min.<ref name="smp" /> A similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at {{convert|1800|C|F}}.<ref name="smas" />

Numerous crystalline binary compounds are known for samarium and one of the group 14, 15, or 16 elements X, where X is Si, Ge, Sn, Pb, Sb or Te, and metallic alloys of samarium form another large group. They are all prepared by annealing mixed powders of the corresponding elements. Many of the resulting compounds are non-stoichiometric and have nominal compositions Sm<sub>a</sub>X<sub>b</sub>, where the b/a ratio varies between 0.5 and 3.<ref>{{cite journal |last1=Gladyshevskii|first1=E. I.|last2=Kripyakevich|first2=P. I.|title=Monosilicides of rare earth metals and their crystal structures|journal=Journal of Structural Chemistry|volume=5|page=789|date=1965|doi=10.1007/BF00744231|issue=6|bibcode=1965JStCh...5..789G |s2cid=93941853}}</ref><ref>{{cite journal|last1=Smith|first1=G. S.|last2=Tharp|first2=A. G.|last3=Johnson|first3=W.|title=Rare earth–germanium and –silicon compounds at 5:4 and 5:3 compositions|journal=Acta Crystallographica|volume=22|page=940|date=1967|doi=10.1107/S0365110X67001902|issue=6|doi-access=free|bibcode=1967AcCry..22..940S }}</ref>

===Organometallic compounds===
Samarium forms a [[Cyclopentadiene|cyclopentadienide]] {{chem2|Sm(C5H5)3}} and its chloroderivatives {{chem2|Sm(C5H5)2Cl}} and {{chem2|Sm(C5H5)Cl2}}. They are prepared by reacting samarium trichloride with {{chem2|NaC5H5}} in [[tetrahydrofuran]]. Contrary to cyclopentadienides of most other lanthanides, in {{chem2|Sm(C5H5)3}} some {{chem2|C5H5}} rings bridge each other by forming ring vertexes η<sup>1</sup> or edges η<sup>2</sup> toward another neighboring samarium, thus creating polymeric chains.<ref name="g1248" /> The chloroderivative {{chem2|Sm(C5H5)2Cl}} has a dimer structure, which is more accurately expressed as {{chem2|(η(5)\sC5H5)2Sm(\m\sCl)2(\h(5)\sC5H5)2}}. There, the chlorine bridges can be replaced, for instance, by iodine, hydrogen or nitrogen atoms or by [[cyanide|CN]] groups.<ref name="g1249">[[#Greenwood|Greenwood]], p. 1249</ref>

The ({{chem2|C5H5}})<sup>−</sup> ion in samarium cyclopentadienides can be replaced by the indenide ({{chem2|C9H7}})<sup>−</sup> or [[Cyclooctatetraene|cyclooctatetraenide]] ({{chem2|C8H8}})<sup>2−</sup> ring, resulting in {{chem2|Sm(C9H7)3}} or {{chem2|KSm(\h(8)\sC8H8)2}}. The latter compound has a structure similar to [[uranocene]]. There is also a cyclopentadienide of divalent samarium, {{chem2|Sm(C5H5)2}} a solid that sublimates at about {{convert|85|C|F}}. Contrary to [[ferrocene]], the {{chem2|C5H5}} rings in {{chem2|Sm(C5H5)2}} are not parallel but are tilted by 40°.<ref name="g1249" /><ref>{{cite journal|last1=Evans|first1=William J.|last2=Hughes|first2=Laura A.|last3=Hanusa|first3=Timothy P.|title=Synthesis and x-ray crystal structure of bis(pentamethylcyclopentadienyl) complexes of samarium and europium: (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Sm and (C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Eu|journal=Organometallics|volume=5|page=1285|date=1986|doi=10.1021/om00138a001|issue=7}}</ref>

A [[Salt metathesis reaction|metathesis reaction]] in tetrahydrofuran or [[diethyl ether|ether]] gives [[alkyl]]s and [[aryl]]s of samarium:<ref name="g1249" />
:{{chem2|SmCl3 + 3LiR → SmR3 + 3LiCl}}
:{{chem2|Sm(OR)3 + 3LiCH(SiMe3)2 → Sm{CH(SiMe3)2}3 + 3LiOR}}

Here R is a hydrocarbon group and Me = [[methyl]].

==Isotopes==
{{main|Isotopes of samarium}}
Naturally occurring samarium is composed of five stable [[isotope]]s: <sup>144</sup>Sm, <sup>149</sup>Sm, <sup>150</sup>Sm, <sup>152</sup>Sm and <sup>154</sup>Sm, and two extremely long-lived [[radioisotope]]s, [[samarium-147|<sup>147</sup>Sm]] (half-life ''t''<sub>1/2</sub>&nbsp;= 1.06{{e|11}} years) and <sup>148</sup>Sm (7{{e|15}} years), with <sup>152</sup>Sm being the most abundant ([[natural abundance|26.75%]]).{{NUBASE2020|ref}} <sup>149</sup>Sm is listed by various sources as being stable,{{NUBASE2020|ref}}<ref>{{Cite web |publisher=Brookhaven National Laboratory |title=Chart of the nuclides |url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=62&n=87 |access-date=2011-02-13 |archive-date=2017-07-29 |archive-url=https://web.archive.org/web/20170729181515/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=62&n=87 |url-status=dead }}</ref> but some sources state that it is radioactive,<ref>Holden, Norman E. "Table of the isotopes" in {{RubberBible86th}}</ref> with a lower bound for its half-life given as {{val|2|e=15}} years.{{NUBASE2020|ref}} Some [[observationally stable]] samarium isotopes are predicted to decay to [[isotopes of neodymium]].<ref name="rare_decays">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |title=Experimental searches for rare alpha and beta decays |date=2019 |journal=[[European Physical Journal A]] |volume=55 |number=140 |pages=4–6 <!--data table-->|doi=10.1140/epja/i2019-12823-2 |arxiv=1908.11458 |bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref> The long-lived isotopes <sup>146</sup>Sm, <sup>147</sup>Sm, and <sup>148</sup>Sm undergo [[alpha decay]] to [[neodymium]] isotopes. Lighter unstable isotopes of samarium mainly decay by [[electron capture]] to [[promethium]], while heavier ones [[beta decay]] to [[europium]].{{NUBASE2020|ref}} The known isotopes range from <sup>129</sup>Sm to <sup>168</sup>Sm.{{NUBASE2020|ref}}<ref name=Ln922>{{cite journal |last1=Kiss |first1=G. G. |last2=Vitéz-Sveiczer |first2=A. |last3=Saito |first3=Y. |display-authors=et al. |title=Measuring the β-decay properties of neutron-rich exotic Pm, Sm, Eu, and Gd isotopes to constrain the nucleosynthesis yields in the rare-earth region |journal=The Astrophysical Journal |volume=936 |issue=107 |date=2022 |page=107 |doi=10.3847/1538-4357/ac80fc |bibcode=2022ApJ...936..107K |s2cid=252108123 |doi-access=free |hdl=2117/375253 |hdl-access=free }}</ref> The half-lives of <sup>151</sup>Sm and <sup>145</sup>Sm are 90 years and 340 days, respectively. All remaining [[radioisotopes]] have half-lives that are less than 2 days, and most these have half-life less than 48 seconds. Samarium also has twelve known [[nuclear isomer]]s, the most stable of which are <sup>141m</sup>Sm ([[half-life]] 22.6 minutes), <sup>143m1</sup>Sm (''t''<sub>1/2</sub>&nbsp;= 66 seconds), and <sup>139m</sup>Sm (''t''<sub>1/2</sub>&nbsp;= 10.7 seconds).{{NUBASE2020|ref}} Natural samarium has a [[Radioactive decay|radioactivity]] of 127&nbsp;[[becquerel|Bq]]/g, mostly due to <sup>147</sup>Sm,<ref name=iaea1512>{{cite report |url=https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1512_web.pdf |title=Radiation Protection and NORM Residue Management in the Production of Rare Earths from Thorium Containing Minerals |publisher=[[International Atomic Energy Agency]] |series=Safety Report Series |number=68 |date=2011 |page=174 |access-date=2022-07-25}}</ref> which [[alpha decay]]s to <sup>143</sup>Nd with a [[half-life]] of 1.06{{e|11}} years and is used in [[samarium–neodymium dating]].<ref name=DePaolo147Sm>{{cite journal|last1=Depaolo|first1=D. J.|last2=Wasserburg|first2=G. J.|title=Nd isotopic variations and petrogenetic models |journal=Geophysical Research Letters|volume=3|pages=249|year=1976|doi=10.1029/GL003i005p00249|bibcode=1976GeoRL...3..249D|issue=5|url=https://authors.library.caltech.edu/41937/1/grl330.pdf}}</ref><ref name=McCulloch147Sm>{{cite journal|last1=McCulloch|first1=M. T.|last2=Wasserburg|first2=G. J. |title=Sm-Nd and Rb-Sr Chronology of Continental Crust Formation |journal=Science |volume=200 |pages=1003–11 |year=1978 |doi=10.1126/science.200.4345.1003 |issue=4345 |pmid=17740673 |bibcode=1978Sci...200.1003M |s2cid=40675318 |url=https://resolver.caltech.edu/CaltechAUTHORS:20131107-143832294 }}</ref> <sup>146</sup>Sm is an [[extinct radionuclide]], with the half-life of 9.20{{e|7}} years.<ref name=Chiera2024/> There have been searches of samarium-146 as a [[primordial nuclide]], because its half-life is long enough such that minute quantities of the element should persist today.<ref>{{cite journal | last=Macfarlane | first=Ronald D. | title=Natural Occurrence of Samarium-146 | journal=Nature | volume=188 | issue=4757 | year=1960 | issn=0028-0836 | doi=10.1038/1881180a0 | pages=1180–1181| bibcode=1960Natur.188.1180M | s2cid=4217617 }}</ref> It can be used in radiometric dating.<ref>{{cite journal |title=Separation of samarium and neodymium: a prerequisite for getting signals from nuclear synthesis |author=Samir Maji |journal=Analyst |volume=131 |pages=1332–1334 |year=2006 |doi=10.1039/b608157f |pmid=17124541 |issue=12 |bibcode=2006Ana...131.1332M |display-authors=1 |last2=Lahiri |first2=Susanta |last3=Wierczinski |first3=Birgit |last4=Korschinek |first4=Gunther}}</ref>

Samarium-149 is an observationally stable isotope of samarium (predicted to decay, but no decays have ever been observed, giving it a half-life at least several orders of magnitude longer than the age of the universe), and a product of the decay chain from the [[fission product]] <sup>149</sup>Nd (yield 1.0888%). <sup>149</sup>Sm is a decay product and [[neutron]]-absorber in [[nuclear reactor]]s, with a [[neutron poison]] effect that is second in importance for reactor design and operation only to [[Xenon-135|<sup>135</sup>Xe]].<ref>{{cite book|title=DOE Fundamentals Handbook: Nuclear Physics and Reactor Theory |date=January 1993 |publisher=[[U.S. Department of Energy]] |url=http://www.hss.energy.gov/nuclearsafety/ns/techstds/standard/hdbk1019/h1019v2.pdf |pages=34, 67 |archive-url=https://web.archive.org/web/20090322040810/http://www.hss.energy.gov/nuclearsafety/ns/techstds/standard/hdbk1019/h1019v2.pdf |archive-date=2009-03-22 }}</ref><ref>{{Cite web |last=K. |first=Khattab |date=2005 |title=Comparison of xenon-135 and samarium-149 poisoning in the Miniature Neutron Source Reactor |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:36069288 |language=Arabic}}</ref> Its [[neutron cross section]] is 41000 [[Barn (unit)|barn]]s for [[thermal neutron]]s.<ref>{{Cite conference |first1=Carlos E. |last1=Espinosa |first2=Bardo E.J. |last2=Bodmann |title=Modeling and simulation of nuclear fuel in scenarios with long time scales |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:46133777 |conference=19. ENFIR: meeting on nuclear reactor physics and thermal hydraulics |language=English}}</ref> Because samarium-149 is not radioactive and is not removed by decay, it presents problems somewhat different from those encountered with xenon-135. The equilibrium concentration (and thus the poisoning effect) builds to an equilibrium value during reactor operations in about 500 hours (about three weeks), and since samarium-149 is stable, its concentration remains essentially constant during reactor operation.<ref>DOE Handbook, pp. 43–47.</ref>

[[File:153Sm-lexidronam structure.svg|thumb|Chemical structure of [[Samarium (153Sm) lexidronam|Sm-EDTMP]]|alt=Chemical structure of samarium (153Sm) lexidronam]]
Samarium-153 is a beta emitter with a half-life of 46.3 hours. It is used to kill cancer cells in [[lung cancer]], [[prostate cancer]], [[breast cancer]], and [[osteosarcoma]]. For this purpose, samarium-153 is [[Chelation|chelated]] with ethylene diamine tetramethylene phosphonate ([[EDTMP]]) and injected intravenously. The chelation prevents accumulation of radioactive samarium in the body that would result in excessive irradiation and generation of new cancer cells.<ref name="emsley" /> The corresponding drug has several names including [[samarium (153Sm) lexidronam|samarium (<sup>153</sup>Sm) lexidronam]]; its [[trade name]] is Quadramet.<ref>{{cite web|access-date=2009-06-06|url=http://www.centerwatch.com/patient/drugs/dru267.html|title=Centerwatch About drug Quadramet|archive-date=2008-10-09|archive-url=https://web.archive.org/web/20081009094258/http://www.centerwatch.com/patient/drugs/dru267.html}}</ref><ref>{{cite journal |last1=Pattison |first1=John E. |title=Finger doses received during 153Sm injections |journal=Health Physics |volume=77 |issue=5 |pages=530–5 |date=1999 |pmid=10524506 |doi=10.1097/00004032-199911000-00006|bibcode=1999HeaPh..77..530P }}</ref><ref>{{cite journal |last1=Finlay |first1=I. G. |last2=Mason |first2=M. D. |last3=Shelley |first3=M. |title=Radioisotopes for the palliation of metastatic bone cancer: a systematic review |journal=The Lancet Oncology |volume=6 |issue=6 |pages=392–400 |date=2005 |pmid=15925817 |doi=10.1016/S1470-2045(05)70206-0}}</ref>

==History==
[[File:Lecoq de Boisbaudran.jpg|thumb|upright|[[Paul Émile Lecoq de Boisbaudran]], the discoverer of samarium | alt=Lecoq de Boisbaudran]]

Detection of samarium and related elements was announced by several scientists in the second half of the 19th century; however, most sources give priority to [[France|French]] chemist [[Paul-Émile Lecoq de Boisbaudran]].<ref>[[#Greenwood|Greenwood]], p. 1229</ref><ref name="brit">[http://www.britannica.com/EBchecked/topic/520309/samarium Samarium], Encyclopædia Britannica on-line</ref> Boisbaudran isolated samarium oxide and/or hydroxide in [[Paris]] in 1879 from the mineral [[samarskite]] {{chem2|((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16}}) and identified a new element in it via sharp optical absorption lines.<ref name="CRC">{{cite book |first=C. R. |last=Hammond |chapter=The Elements |title=Handbook of Chemistry and Physics |edition=81st |publisher=CRC press |isbn=978-0-8493-0481-1 |chapter-url-access=registration |chapter-url=https://archive.org/details/crchandbookofche81lide |date=2004-06-29 |pages=4–27 |location=Boca Raton New York Washington }}</ref> Swiss chemist [[Marc Delafontaine]] announced a new element ''[[decipium]]'' (from {{langx|la|decipiens}} meaning "deceptive, misleading") in 1878,<ref>{{cite journal |title=Sur le décepium, métal nouveau de la samarskite |first=Marc |last=Delafontaine |journal=Journal de pharmacie et de chimie |volume=28 |page=540 |date=1878 |url=https://gallica.bnf.fr/ark:/12148/bpt6k78100m.image.r=Decipium.f548.langEN |language=fr}}</ref><ref>{{cite journal |title=Sur le décepium, métal nouveau de la samarskite |first=Marc |last=Delafontaine |journal=Comptes rendus hebdomadaires des séances de l'Académie des Sciences |volume=87 |page=632 |date=1878 |url=https://gallica.bnf.fr/ark:/12148/bpt6k3044x.image.r=Decipium.f694.langEN |language=fr}}</ref> but later in 1880–1881 demonstrated that it was a mix of several elements, one being identical to Boisbaudran's samarium.<ref name="iupac">{{CIAAW2003}}</ref><ref>{{cite journal|title=Sur le décipium et le samarium |first=Marc |last=Delafontaine |journal=Comptes rendus hebdomadaires des séances de l'Académie des Sciences |volume=93 |page=63 |date=1881 |language=fr |url=https://gallica.bnf.fr/ark:/12148/bpt6k3049g.image.r=Decipium.f63.langEN}}</ref> Though samarskite was first found in the [[Ural Mountains]] in [[Russia]], by the late 1870s it had been found in other places, making it available to many researchers. In particular, it was found that the samarium isolated by Boisbaudran was also impure and had a comparable amount of [[europium]]. The pure samarium(III) oxide was produced only in 1901 by [[Eugène-Anatole Demarçay]],<ref name="van" /><ref name="Weeks">{{cite book |last1=Weeks |first1=Mary Elvira |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |location=Easton, PA |url=https://archive.org/details/discoveryoftheel002045mbp |edition=6th}}</ref><ref name="XIII">{{cite journal |title=The discovery of the elements. XIII. Some elements predicted by Mendeleeff |pages=1605–1619 |last=Weeks |first=Mary Elvira |author-link=Mary Elvira Weeks |doi=10.1021/ed009p1605 |journal=[[Journal of Chemical Education]] |volume=9 |issue=9 |date=1932 |bibcode=1932JChEd...9.1605W}}</ref> and in 1903 Wilhelm Muthmann isolated the element.

Boisbaudran named his element ''samarium'' after the mineral samarskite, which in turn honored [[Vassili Samarsky-Bykhovets]] (1803–1870). Samarsky-Bykhovets, as the Chief of Staff of the [[Russia]]n Corps of Mining Engineers, had granted access for two German mineralogists, the brothers [[Gustav Rose|Gustav]] and [[Heinrich Rose]], to study the mineral samples from the Urals.<ref name="bse">[https://bse.sci-lib.com/article099149.html Samarskite], [[Great Soviet Encyclopedia]] (in Russian)</ref><ref>{{cite journal|url= https://gallica.bnf.fr/ark:/12148/bpt6k3046j/f214.pagination|first= Lecoq de|last= Boisbaudran|title= Recherches sur le samarium, radical d'une terre nouvelle extraite de la samarskite|journal= Comptes rendus hebdomadaires des séances de l'Académie des sciences|volume= 89|date=1879|pages= 212–214}}</ref><ref>Shipley, Joseph Twadell. [https://books.google.com/books?id=m1UKpE4YEkEC&pg=PA90 ''The Origins of English Words: A Discursive Dictionary of Indo-European Roots''], JHU Press, 2001, p.90. {{ISBN|0-8018-6784-3}}</ref> Samarium was thus the first chemical element to be named after a person.<ref name="van" /><ref name="RSC" /> The word ''samaria'' is sometimes used to mean samarium(III) oxide, by analogy with [[yttria]], [[zirconia]], [[alumina]], [[ceria]], [[Holmium(III) oxide|holmia]], etc. The symbol ''Sm'' was suggested for samarium, but an alternative ''Sa'' was often used instead until the 1920s.<ref name="van">[https://elements.vanderkrogt.net/element.php?sym=Sm Samarium: History & Etymology]. Elements.vanderkrogt.net. Retrieved on 2013-03-21.</ref><ref>{{cite journal|last1=Coplen|first1=T. B.|last2=Peiser|first2=H. S.|title=History of the recommended atomic-weight values from 1882 to 1997: A comparison of differences from current values to the estimated uncertainties of earlier values (Technical Report)|journal=Pure and Applied Chemistry |volume=70 |page=237 |date=1998|doi=10.1351/pac199870010237|s2cid=96729044|url=https://zenodo.org/record/1236255|doi-access=free}}</ref>

Before the advent of [[ion-exchange]] separation technology in the 1950s, pure samarium had no commercial uses. However, a by-product of fractional crystallization purification of neodymium was a mix of samarium and gadolinium that got the name "Lindsay Mix" after the company that made it, and was used for nuclear [[control rod]]s in some early nuclear reactors.<ref>{{Cite journal |last1=Ghaemi |first1=Arezoo |last2=Tavakkoli |first2=Haman |last3=Rajabi |first3=Negar |date=2015-06-01 |title=Solvent influence upon complex formation between 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane with samarium(III) metal cation in binary mixed non-aqueous solvents |journal=Russian Journal of Applied Chemistry |language=en |volume=88 |issue=6 |pages=977–984 |doi=10.1134/S1070427215060130 |s2cid=97051960 |issn=1608-3296}}</ref> Nowadays, a similar commodity product has the name "samarium-europium-[[gadolinium]]" (SEG) concentrate.<ref name="RSC">{{Cite web |title=Chemistry in Its Element - Samarium |url=http://www.rsc.org/chemistryworld/podcast/Interactive_Periodic_Table_Transcripts/Samarium.asp |archive-url=https://web.archive.org/web/20160304045647/http://www.rsc.org/chemistryworld/podcast/Interactive_Periodic_Table_Transcripts/Samarium.asp |archive-date=4 March 2016}}</ref> It is prepared by solvent extraction from the mixed [[lanthanide]]s isolated from bastnäsite (or monazite). Since heavier lanthanides have more affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent. Not all rare-earth producers who process bastnäsite do so on a large enough scale to continue by separating the components of SEG, which typically makes up only 1{{endash}}2% of the original ore. Such producers therefore make SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium in the ore is rescued for use in making [[phosphor]]. Samarium purification follows the removal of the europium. {{As of | 2012}}, being in oversupply, samarium oxide is cheaper on a commercial scale than its relative abundance in the ore might suggest.<ref name="price" />

==Occurrence and production==
[[File:Samarskite-fresh.jpg|thumb|Samarskite|alt=Samarskite]]
Samarium concentration in soils varies between 2 and 23&nbsp;ppm, and oceans contain about 0.5–0.8&nbsp;parts per trillion.<ref name="emsley" /> The median value for its [[Abundance of elements in Earth's crust|abundance in the Earth's crust]] used by the CRC Handbook is 7 parts per million (ppm)<ref name=CRCabundance>ABUNDANCE OF ELEMENTS IN THE EARTH’S CRUST AND IN THE SEA, ''CRC Handbook of Chemistry and Physics,'' 97th edition (2016–2017), p. 14-17</ref> and is the 40th most abundant element.<ref>{{Cite book |last=Emsley |first=John |url=https://books.google.com/books?id=2EfYXzwPo3UC&dq=%2240th+most+abundant+element%22&pg=PA466 |title=Nature's Building Blocks: An A-Z Guide to the Elements |date=2011-08-25 |publisher=OUP Oxford |isbn=978-0-19-960563-7 |language=en}}</ref> Distribution of samarium in soils strongly depends on its chemical state and is very inhomogeneous: in sandy soils, samarium concentration is about 200 times higher at the surface of soil particles than in the water trapped between them, and this ratio can exceed 1,000 in clays.<ref name="LA2" />

Samarium is not found free in nature, but, like other rare earth elements, is contained in many minerals, including [[monazite]], [[bastnäsite]], [[cerite]], [[gadolinite]] and [[samarskite]]; monazite (in which samarium occurs at concentrations of up to 2.8%)<ref name="CRC" /> and bastnäsite are mostly used as commercial sources. World resources of samarium are estimated at two million [[tonne]]s; they are mostly located in China, US, Brazil, India, Sri Lanka and Australia, and the annual production is about 700 tonnes.<ref name="emsley" /> Country production reports are usually given for all rare-earth metals combined. By far, China has the largest production with 120,000 tonnes mined per year; it is followed by the US (about 5,000&nbsp;tonnes)<ref name="LA2" /> and India (2,700&nbsp;tonnes).<ref>{{cite web|url=http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/mcs-2010-raree.pdf|title=Rare Earths |publisher=United States Geological Survey|date=January 2010|access-date=2010-12-10}}</ref> Samarium is usually sold as oxide, which at the price of about US$30/kg is one of the cheapest lanthanide oxides.<ref name="price">[https://web.archive.org/web/20121014122537/http://lynascorp.com/page.asp?category_id=1&page_id=25 What are their prices?], Lynas corp.</ref> Whereas [[mischmetal]] – a mixture of rare earth metals containing about 1% of samarium – has long been used, relatively pure samarium has been isolated only recently, through [[ion exchange]] processes, [[solvent extraction]] techniques, and [[electrochemical deposition]]. The metal is often prepared by electrolysis of a molten mixture of [[samarium(III) chloride]] with [[sodium chloride]] or [[calcium chloride]]. Samarium can also be obtained by reducing its oxide with [[lanthanum]]. The product is then distilled to separate samarium (boiling point 1794&nbsp;°C) and lanthanum (b.p.&nbsp;3464&nbsp;°C).<ref name="brit" />

Very few minerals have samarium being the most dominant element. Minerals with essential (dominant) samarium include [[monazite-(Sm)]] and [[florencite-(Sm)]]. These minerals are very rare and are usually found containing other elements, usually [[cerium]] or [[neodymium]].<ref>{{Cite journal |last1=Masau |first1=M. |last2=Cerny |first2=P. |last3=Cooper |first3=M. A. |last4=Chapman |first4=R. |last5=Grice |first5=J. D. |date=2002-12-01 |title=MONAZITE-(Sm), A NEW MEMBER OF THE MONAZITE GROUP FROM THE ANNIE CLAIM #3 GRANITIC PEGMATITE, SOUTHEASTERN MANITOBA |url=http://www.canmin.org/cgi/doi/10.2113/gscanmin.40.6.1649 |journal=The Canadian Mineralogist |language=en |volume=40 |issue=6 |pages=1649–1655 |doi=10.2113/gscanmin.40.6.1649 |bibcode=2002CaMin..40.1649M |issn=0008-4476}}</ref><ref>{{Cite journal |last1=Repina |first1=S. A. |last2=Popova |first2=V. I. |last3=Churin |first3=E. I. |last4=Belogub |first4=E. V. |last5=Khiller |first5=V. V. |date=December 2011 |title=Florencite-(Sm)—(Sm,Nd)Al<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>: a new mineral species of the alunite–jarosite group from the subpolar Urals |url=https://link.springer.com/10.1134/S1075701511070191 |journal=Geology of Ore Deposits |language=en |volume=53 |issue=7 |pages=564–574 |doi=10.1134/S1075701511070191 |bibcode=2011GeoOD..53..564R |s2cid=97229772 |issn=1075-7015|url-access=subscription }}</ref><ref>{{cite web|url=http://www.mindat.org/min-11438.html |title=Monazite-(Sm): Monazite-(Sm) mineral information and data |website=Mindat.org |access-date=2016-03-04}}</ref><ref>{{cite web|url=http://www.mindat.org/min-42495.html |title=Florencite-(Sm): Florencite-(Sm) mineral information and data |website=Mindat.org |access-date=2016-03-04}}</ref> It is also made by [[neutron capture]] by samarium-149, which is added to the [[control rod]]s of nuclear reactors. Therefore, {{sup|151}}Sm is present in spent [[nuclear fuel]] and radioactive waste.<ref name="LA2" />

==Applications==
[[File:Samariumiodide.jpg|thumb|[[Barbier reaction]] using {{chem2|SmI2}}|alt=Barbier reaction using samarium diiodide]]

===Magnets===
An important use of samarium is [[samarium–cobalt magnet]]s, which are nominally {{chem2|SmCo5}} or {{chem2|Sm2Co17}}.<ref>{{cite web |url=https://www.stanfordmagnets.com/two-grades-of-samarium-cobalt-magnets-smco5-sm2co17.html |title=Two Grades of Samarium Cobalt Magnets: SmCo5 & Sm2Co17 |last=Marchio |first=Cathy |date=Apr 16, 2024 |website=Stanford Magnets |access-date=Aug 23, 2024}}</ref> They have high permanent magnetization, about 10,000 times that of iron and second only to [[neodymium magnet]]s. However, samarium magnets resist demagnetization better; they are stable to temperatures above {{convert|700|C|F}} (cf. 300–400&nbsp;°C for neodymium magnets). These magnets are found in small motors, headphones, and high-end magnetic [[Pick up (music technology)|pickup]]s for guitars and related musical instruments.<ref name="emsley" /> For example, they are used in the motors of a [[solar power|solar-powered]] [[electric aircraft]], the [[Solar Challenger]], and in the [[Vintage Noiseless|Samarium Cobalt Noiseless]] electric guitar and bass pickups.

===Chemical reagent===
Samarium and its compounds are important as catalysts and [[chemical reagent]]s. Samarium catalysts help the decomposition of plastics, dechlorination of pollutants such as [[polychlorinated biphenyl]]s (PCB), as well as dehydration and [[dehydrogenation]] of ethanol.<ref name="CRC" /> [[Lanthanide trifluoromethanesulfonates|Samarium(III) triflate]] {{chem2|Sm(OTf)3}}, that is {{chem2|Sm(CF3SO3)3}}, is one of the most efficient [[Lewis acid]] catalysts for a halogen-promoted [[Friedel–Crafts reaction]] with alkenes.<ref>{{cite journal|last1=Hajra |first1=S.|last2=Maji |first2=B.|last3=Bar |first3=S. |title=Samarium Triflate-Catalyzed Halogen-Promoted Friedel-Crafts Alkylation with Alkenes|date=2007|journal= [[Org. Lett.]]|volume= 9|issue= 15|pages= 2783–2786|doi= 10.1021/ol070813t|pmid=17585769}}</ref> [[Samarium(II) iodide]] is a very common reducing and coupling agent in [[organic synthesis]], for example in [[desulfonylation reactions]]; [[annulation]]; [[Danishefsky Taxol total synthesis|Danishefsky]], [[Kuwajima Taxol total synthesis|Kuwajima]], [[Mukaiyama Taxol total synthesis|Mukaiyama]] and [[Holton Taxol total synthesis|Holton Taxol total syntheses]]; [[strychnine total synthesis]]; [[Barbier reaction]] and other [[reductions with samarium(II) iodide]].<ref>{{cite book| page=1128| url=https://books.google.com/books?id=U3MWRONWAmMC&pg=PA1128|title =Advanced inorganic chemistry |edition=6th |last1= Cotton|first1=F. Albert |last2=Wilkinson |first2=Geoffrey |last3=Murillo |first3=Carlos A. |last4=Bochmann |first4=Manfred |publisher= Wiley|location=New Delhi, India|date=2007|isbn =978-81-265-1338-3}}</ref>

In its usual oxidized form, samarium is added to ceramics and glasses where it increases absorption of infrared light. As a (minor) part of [[mischmetal]], samarium is found in the "[[flint]]" ignition devices of many [[lighter]]s and torches.<ref name="emsley" /><ref name="CRC" />

===Neutron absorber===
Samarium-149 has a high [[neutron capture cross section|cross section for neutron capture]] (41,000&nbsp;[[barn (unit)|barns]]) and so is used in control rods of [[nuclear reactor]]s. Its advantage compared to competing materials, such as boron and cadmium, is stability of absorption – most of the fusion products of {{sup|149}}Sm are other isotopes of samarium that are also good [[neutron absorber]]s. For example, the cross section of samarium-151 is 15,000&nbsp;barns, it is on the order of hundreds of barns for {{sup|150}}Sm, {{sup|152}}Sm, and {{sup|153}}Sm, and 6,800&nbsp;barns for natural (mixed-isotope) samarium.<ref name="CRC" /><ref name="LA2" /><ref>[https://web.archive.org/web/20110706160607/http://www-nds.ipen.br/sgnucdat/b3.pdf Thermal neutron capture cross sections and resonance integrals – Fission product nuclear data]. ipen.br</ref>

===Lasers===
Samarium-doped [[calcium fluoride]] crystals were used as an active medium in one of the first [[solid-state laser]]s designed and built by [[Peter Sorokin]] (co-inventor of the [[dye laser]]) and Mirek Stevenson at [[IBM]] research labs in early 1961. This samarium laser gave pulses of red light at 708.5&nbsp;nm. It had to be cooled by liquid helium and so did not find practical applications.<ref>Bud, Robert and Gummett, Philip [https://books.google.com/books?id=HMx_6FtHBcUC&pg=PA268 ''Cold War, Hot Science: Applied Research in Britain's Defence Laboratories, 1945–1990''], NMSI Trading Ltd, 2002 {{ISBN|1-900747-47-2}} p. 268</ref><ref>{{cite journal|last1=Sorokin|first1=P. P.|title=Contributions of IBM to Laser Science—1960 to the Present|journal=IBM Journal of Research and Development|volume=23|page=476|date=1979|doi=10.1147/rd.235.0476|issue=5|bibcode=1979IBMJ...23..476S}}</ref> Another samarium-based laser became the first saturated [[X-ray laser]] operating at wavelengths shorter than 10 nanometers. It gave 50-picosecond pulses at 7.3 and 6.8&nbsp;nm suitable for uses in [[holography]], high-resolution [[microscopy]] of biological specimens, [[deflectometry]], [[interferometry]], and [[radiography]] of dense plasmas related to confinement fusion and [[astrophysics]]. Saturated operation meant that the maximum possible power was extracted from the lasing medium, resulting in the high peak energy of 0.3&nbsp;mJ. The active medium was samarium plasma produced by irradiating samarium-coated glass with a pulsed infrared [[Nd:YAG laser|Nd-glass laser]] (wavelength ~1.05&nbsp;μm).<ref>{{cite journal |last=Zhang |first=J. |title=A Saturated X-ray Laser Beam at 7 Nanometers |journal=Science |volume=276 |page=1097 |date=1997 |doi=10.1126/science.276.5315.1097 |issue=5315}}</ref>

===Storage phosphor===
In 2007 it was shown that nanocrystalline BaFCl:Sm{{sup|3+}} as prepared by co-precipitation can serve as a very efficient X-ray [[Photostimulated luminescence|storage phosphor]].<ref>{{cite journal|last1=Riesen|first1=Hans |last2=Kaczmarek|first2=Wieslaw |title=Efficient X-ray Generation of Sm{{sup|2+}} in Nanocrystalline BaFCl/Sm{{sup|3+}}: a Photoluminescent X-ray Storage Phosphor|journal=Inorganic Chemistry|date=2007-08-02|volume=46|issue=18|pages=7235–7 |doi=10.1021/ic062455g|pmid=17672448}}</ref> The co-precipitation leads to nanocrystallites of the order of 100–200&nbsp;nm in size and their sensitivity as X-ray storage phosphors is increased a remarkable ~500,000 times because of the specific arrangements and density of defect centers in comparison with microcrystalline samples prepared by sintering at high temperature.<ref>{{cite journal|last1=Liu|first1=Zhiqiang |last2=Stevens-Kalceff|first2=Marion |last3=Riesen|first3=Hans |title=Photoluminescence and Cathodoluminescence Properties of Nanocrystalline BaFCl:Sm3+ X-ray Storage Phosphor|journal=Journal of Physical Chemistry C|date=2012-03-16|volume=116|issue=14 |pages=8322–8331|doi=10.1021/jp301338b}}</ref> The mechanism is based on reduction of Sm{{sup|3+}} to Sm{{sup|2+}} by trapping electrons that are created upon exposure to ionizing radiation in the BaFCl host. The {{sup|5}}D{{sub|J}}–{{sup|7}}F{{sub|J}} f–f luminescence lines can be very efficiently excited via the parity allowed 4f{{sup|6}}→4f{{sup|5}}5d transition at ~417&nbsp;nm. The latter wavelength is ideal for efficient excitation by blue-violet laser diodes as the transition is electric dipole allowed and thus relatively intense (400 L/(mol⋅cm)).<ref>{{cite journal|last1=Wang|first1=Xianglei |last2=Liu|first2=Zhiqiang |last3=Stevens-Kalceff|first3=Marion |last4=Riesen|first4=Hans |title=Mechanochemical Preparation of Nanocrystalline BaFCl Doped with Samarium in the 2+ Oxidation State|journal=Inorganic Chemistry|date=August 12, 2014 |volume=53|issue=17|pages=8839–8841 |doi=10.1021/ic500712b|pmid=25113662}}</ref>
The phosphor has potential applications in personal dosimetry, dosimetry and imaging in radiotherapy, and medical imaging.<ref>{{cite web|title=Dosimetry&Imaging Pty Ltd|url=http://www.oelimaging.com |access-date=2018-11-28|archive-url= https://web.archive.org/web/20170926094926/http://oelimaging.com/ |archive-date=2017-09-26}}</ref>

===Non-commercial and potential uses===

* The change in electrical resistivity in [[samarium monochalcogenides]] can be used in a pressure sensor or in a memory device triggered between a low-resistance and high-resistance state by external pressure,<ref>{{Cite patent|number=20100073997|title=Piezo-Driven Non-Volatile Memory Cell with Hysteretic Resistance|gdate=2010-03-25|invent1=Elmegreen|invent2=Krusin-elbaum|invent3=Liu|invent4=Martyna|inventor1-first=Bruce G.|inventor2-first=Lia|inventor3-first=Xiao Hu|inventor4-first=Glenn J.|url=https://www.freepatentsonline.com/y2010/0073997.html}}</ref> and such devices are being developed commercially.<ref>{{Cite web |title=About us |url=https://tenzo-sms.ru/en/about |access-date=2022-12-31 |website=tenzo-sms.ru}}</ref> Samarium monosulfide also generates electric voltage upon moderate heating to about {{convert|150|C|F}} that can be applied in [[Thermoelectric generator|thermoelectric power converters]].<ref>{{cite journal|last1=Kaminskii|first1=V. V. |last2=Solov'ev |first2=S. M. |last3=Golubkov|first3=A. V.|title=Electromotive Force Generation in Homogeneously Heated Semiconducting Samarium Monosulfide |doi=10.1134/1.1467284 |date=2002 |page=229 |volume=28 |journal=Technical Physics Letters |url=http://www.tenzo-sms.ru/en/articles/5 |issue=3 |bibcode=2002TePhL..28..229K |s2cid=122463906 |archive-url=https://web.archive.org/web/20120315180549/http://www.tenzo-sms.ru/en/articles/5 |archive-date=2012-03-15|url-access=subscription }}</ref>
* Analysis of relative concentrations of samarium and neodymium isotopes {{sup|147}}Sm, {{sup|144}}Nd, and {{sup|143}}Nd allows determination of the age and origin of rocks and meteorites in [[samarium–neodymium dating]]. Both elements are lanthanides and are very similar physically and chemically. Thus, Sm–Nd dating is either insensitive to partitioning of the marker elements during various geologic processes, or such partitioning can well be understood and modeled from the [[ionic radius|ionic radii]] of said elements.<ref>Bowen, Robert and Attendorn, H -G [https://books.google.com/books?id=k90iAnFereYC&pg=PA270 ''Isotopes in the Earth Sciences''], Springer, 1988, {{ISBN|0-412-53710-9}}, pp. 270 ff</ref>
* The Sm{{sup|3+}} ion is a potential [[Activator (phosphor)|activator]] for use in warm-white light emitting diodes. It offers high [[luminous efficacy]] due to narrow emission bands; but the generally low [[quantum efficiency]] and too little absorption in the [[Ultraviolet#Subtypes|UV-A]] to blue spectral region hinders commercial application.<ref>{{cite journal|last1=Baur|first1=F.|last2=Katelnikovas|first2=A. |last3=Sazirnakovas|first3=S. |last4=Jüstel|first4=T. |title=Synthesis and Optical Properties of Li{{sub|3}}Ba{{sub|2}}La{{sub|3}}(MoO{{sub|4}}){{sub|8}}:Sm{{sup|3+}} |journal=Zeitschrift für Naturforschung B |volume=69|pages=183–192 |date=2014|doi=10.5560/ZNB.2014-3279|issue=2|s2cid=197099937}}</ref>
* Samarium is used for [[ionosphere]] testing. A rocket spreads samarium monoxide as a red vapor at high altitude, and researchers test how the atmosphere disperses it and how it impacts radio transmissions.<ref>{{cite journal |last1=Caton |first1=Ronald G. |last2=Pedersen |first2=Todd R. |last3=Groves |first3=Keith M. |last4=Hines |first4=Jack |last5=Cannon |first5=Paul S. |last6=Jackson-Booth |first6=Natasha |last7=Parris |first7=Richard T. |last8=Holmes |first8=Jeffrey M. |last9=Su |first9=Yi-Jiun |last10=Mishin |first10=Evgeny V. |last11=Roddy |first11=Patrick A. |last12=Viggiano |first12=Albert A. |last13=Shuman |first13=Nicholas S. |last14=Ard |first14=Shaun G. |last15=Bernhardt |first15=Paul A. |last16=Siefring |first16=Carl L. |last17=Retterer |first17=John |last18=Kudeki |first18=Erhan |last19=Reyes |first19=Pablo M. |title=Artificial ionospheric modification: The Metal Oxide Space Cloud experiment |journal=Radio Science |date=May 2017 |volume=52 |issue=5 |pages=539–558 |doi=10.1002/2016rs005988|url=https://pure-oai.bham.ac.uk/ws/files/40897676/Caton_et_al_2017_Radio_Science.pdf |bibcode=2017RaSc...52..539C |s2cid=55195732 }}</ref><ref>{{cite web |last1=Zell |first1=Holly |title=First of Four Sounding Rockets Launched from the Marshall Islands |url=https://www.nasa.gov/mission_pages/sounding-rockets/news/mosc.html |website=NASA |language=en |date=2013-06-07 |access-date=2019-08-15 |archive-date=2021-10-11 |archive-url=https://web.archive.org/web/20211011040155/https://www.nasa.gov/mission_pages/sounding-rockets/news/mosc.html |url-status=dead }}</ref>
* Samarium hexaboride, {{chem2|SmB6}}, has recently been shown to be a [[topological insulator]] with potential uses in [[quantum computing]].<ref name="physorgsamarium">{{Cite journal |last1=Li |first1=G. |last2=Xiang |first2=Z. |last3=Yu |first3=F. |last4=Asaba |first4=T. |last5=Lawson |first5=B. |last6=Cai |first6=P. |last7=Tinsman |first7=C. |last8=Berkley |first8=A. |last9=Wolgast |first9=S. |last10=Eo |first10=Y. S. |last11=Kim |first11=Dae-Jeong |last12=Kurdak |first12=C. |last13=Allen |first13=J. W. |last14=Sun |first14=K. |last15=Chen |first15=X. H. |date=2014-12-05 |title=Two-dimensional Fermi surfaces in Kondo insulator SmB 6 |url=https://www.science.org/doi/10.1126/science.1250366 |journal=Science |language=en |volume=346 |issue=6214 |pages=1208–1212 |doi=10.1126/science.1250366 |pmid=25477456 |arxiv=1306.5221 |bibcode=2014Sci...346.1208L |s2cid=119191689 |issn=0036-8075}}</ref><ref>{{Cite journal|last1=Botimer|arxiv=1211.6769 |first1=J. |last2=Kim |first2=D. J. |last3=Thomas  |first3=S. |last4=Grant |first4=T. |last5=Fisk |first5=Z. |author6=Jing Xia |title=Robust Surface Hall Effect and Nonlocal Transport in SmB<sub>6</sub>: Indication for an Ideal Topological Insulator |journal=Scientific Reports |volume=3 |issue=3150 |pages=3150 |year=2013|doi=10.1038/srep03150 |bibcode=2013NatSR...3.3150K |pmid=24193196 |pmc=3818682}}</ref><ref>{{cite journal |last1=Zhang |first1=Xiaohang |last2=Butch |first2=N. P. |last3=Syers |first3=P. |last4=Ziemak |first4=S. |last5=Greene |first5=Richard L. |last6=Paglione |first6=Johnpierre |title=Hybridization, Correlation, and In-Gap States in the Kondo Insulator SmB<sub>6</sub> |year=2013 |doi=10.1103/PhysRevX.3.011011 |journal=Physical Review X |volume=3 |issue=1|pages=011011 |arxiv=1211.5532|bibcode=2013PhRvX...3a1011Z |s2cid=53638956 }}</ref><ref>{{Cite journal |arxiv=1211.5104 |first1=Steven |last1=Wolgast |first2=Cagliyan |last2=Kurdak |first3=Kai |last3=Sun |first4=J. W. |last4=Allen |first5=Dae-Jeong |last5=Kim |first6=Zachary |last6=Fisk |title=Low-temperature surface conduction in the Kondo insulator SmB<sub>6</sub>|journal=Physical Review B |volume=88 |issue=18 |pages=180405 |date=2012 |display-authors=3|doi=10.1103/PhysRevB.88.180405 |bibcode=2013PhRvB..88r0405W |s2cid=119242604 }}</ref>

== Biological role and precautions ==
{{Chembox
| container_only = yes
|Section7={{Chembox Hazards
| Hazards_ref = <ref>{{Sigma-Aldrich|id=263184|name=Samarium 263184|access-date=2023-04-11}}</ref>
| ExternalSDS =
| GHSPictograms = {{GHS02}}
| GHSSignalWord = Warning<!-- source fisherthermop says 'danger'? (11Apr2023) -->
| HPhrases = {{H-phrases|261}}
| PPhrases = {{P-phrases|P231 + P232|P280|P370 + P378|P501}}
| NFPA-H = 2
| NFPA-F = 3
| NFPA-R = 2
| NFPA-S = W
| NFPA_ref = <ref>{{cite web|url=https://www.fishersci.com/store/msds?partNumber=AA40297DH&productDescription=SAMR+RD+6.35MMDIA+99.9+25MM&vendorId=VN00024248&countryCode=US&language=en |title=Safety Data Sheet |access-date=2023-04-11 |date=2020-02-14 |publisher=Thermo Fisher Scientific }}</ref>
 }}
}}
Samarium salts stimulate metabolism, but it is unclear whether this is from samarium or other lanthanides present with it. The total amount of samarium in adults is about 50&nbsp;[[microgram|μg]], mostly in liver and kidneys and with ~8&nbsp;μg/L being dissolved in blood. Samarium is not absorbed by plants to a measurable concentration and so is normally not part of human diet. However, a few plants and vegetables may contain up to 1 part per million of samarium. Insoluble salts of samarium are non-toxic and the soluble ones are only slightly toxic.<ref name="emsley">{{cite book|title= Nature's Building Blocks: An A–Z Guide to the Elements|last= Emsley|first= John|publisher= Oxford University Press|date=2001|location= Oxford, England, UK|isbn= 0-19-850340-7|chapter= Samarium|pages= [https://archive.org/details/naturesbuildingb0000emsl/page/371 371–374]|chapter-url= https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA371|url= https://archive.org/details/naturesbuildingb0000emsl/page/371}}</ref><ref name="Bayouth">{{cite journal |last1=Bayouth |first1=J. E. |last2=Macey |first2=D. J. |last3=Kasi |first3=L. P. |last4=Fossella |first4=F. V. |title=Dosimetry and toxicity of samarium-153-EDTMP administered for bone pain due to skeletal metastases |journal=Journal of Nuclear Medicine |year=1994 |volume=35 |issue=1 |pages=63–69 |url=https://jnm.snmjournals.org/content/35/1/63.long |pmid=7505819}}</ref> When ingested, only 0.05% of samarium salts are absorbed into the bloodstream and the remainder are excreted. From the blood, 45% goes to the liver and 45% is deposited on the surface of the bones where it remains for 10 years; the remaining 10% is excreted.<ref name="LA2">[http://www.ead.anl.gov/pub/doc/samarium.pdf Human Health Fact Sheet on Samarium] {{webarchive|url=https://web.archive.org/web/20120407032958/http://www.ead.anl.gov/pub/doc/samarium.pdf |date=2012-04-07 }}, Los Alamos National Laboratory</ref>
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==References==
{{reflist}}

==Bibliography==
*{{cite book|ref=Greenwood|last1=Greenwood |first1=Norman N.|last2=Earnshaw |first2=Alan |date=1997|title= Chemistry of the Elements |edition=2nd|publisher= Butterworth–Heinemann|isbn=  9780080379418}}

==External links==
{{sister project links|d=Q1819|v=The_periodic_table/Samarium|voy=no|q=no|wikt=samarium|s=no|b=no|n=no|c=Samarium|m=no|mw=no|species=no}}
*[https://education.jlab.org/itselemental/ele062.html It's Elemental&nbsp;– Samarium]
*[https://www.organic-chemistry.org/chemicals/reductions/samariumlowvalent.shtm Reducing Agents > Samarium low valent]
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{{Periodic table (navbox)}}
{{Samarium compounds}}
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[[Category:Samarium| ]]
[[Category:Chemical elements]]
[[Category:Chemical elements with rhombohedral structure]]
[[Category:Lanthanides]]
[[Category:Reducing agents]]