Samarium


Samarium
promethiumsamariumeuropium
-

Sm

Pu
Element 1: Hydrogen (H), Other non-metal
Element 2: Helium (He), Noble gas
Element 3: Lithium (Li), Alkali metal
Element 4: Beryllium (Be), Alkaline earth metal
Element 5: Boron (B), Metalloid
Element 6: Carbon (C), Other non-metal
Element 7: Nitrogen (N), Other non-metal
Element 8: Oxygen (O), Other non-metal
Element 9: Fluorine (F), Halogen
Element 10: Neon (Ne), Noble gas
Element 11: Sodium (Na), Alkali metal
Element 12: Magnesium (Mg), Alkaline earth metal
Element 13: Aluminium (Al), Other metal
Element 14: Silicon (Si), Metalloid
Element 15: Phosphorus (P), Other non-metal
Element 16: Sulfur (S), Other non-metal
Element 17: Chlorine (Cl), Halogen
Element 18: Argon (Ar), Noble gas
Element 19: Potassium (K), Alkali metal
Element 20: Calcium (Ca), Alkaline earth metal
Element 21: Scandium (Sc), Transition metal
Element 22: Titanium (Ti), Transition metal
Element 23: Vanadium (V), Transition metal
Element 24: Chromium (Cr), Transition metal
Element 25: Manganese (Mn), Transition metal
Element 26: Iron (Fe), Transition metal
Element 27: Cobalt (Co), Transition metal
Element 28: Nickel (Ni), Transition metal
Element 29: Copper (Cu), Transition metal
Element 30: Zinc (Zn), Transition metal
Element 31: Gallium (Ga), Other metal
Element 32: Germanium (Ge), Metalloid
Element 33: Arsenic (As), Metalloid
Element 34: Selenium (Se), Other non-metal
Element 35: Bromine (Br), Halogen
Element 36: Krypton (Kr), Noble gas
Element 37: Rubidium (Rb), Alkali metal
Element 38: Strontium (Sr), Alkaline earth metal
Element 39: Yttrium (Y), Transition metal
Element 40: Zirconium (Zr), Transition metal
Element 41: Niobium (Nb), Transition metal
Element 42: Molybdenum (Mo), Transition metal
Element 43: Technetium (Tc), Transition metal
Element 44: Ruthenium (Ru), Transition metal
Element 45: Rhodium (Rh), Transition metal
Element 46: Palladium (Pd), Transition metal
Element 47: Silver (Ag), Transition metal
Element 48: Cadmium (Cd), Transition metal
Element 49: Indium (In), Other metal
Element 50: Tin (Sn), Other metal
Element 51: Antimony (Sb), Metalloid
Element 52: Tellurium (Te), Metalloid
Element 53: Iodine (I), Halogen
Element 54: Xenon (Xe), Noble gas
Element 55: Caesium (Cs), Alkali metal
Element 56: Barium (Ba), Alkaline earth metal
Element 57: Lanthanum (La), Lanthanoid
Element 58: Cerium (Ce), Lanthanoid
Element 59: Praseodymium (Pr), Lanthanoid
Element 60: Neodymium (Nd), Lanthanoid
Element 61: Promethium (Pm), Lanthanoid
Element 62: Samarium (Sm), Lanthanoid
Element 63: Europium (Eu), Lanthanoid
Element 64: Gadolinium (Gd), Lanthanoid
Element 65: Terbium (Tb), Lanthanoid
Element 66: Dysprosium (Dy), Lanthanoid
Element 67: Holmium (Ho), Lanthanoid
Element 68: Erbium (Er), Lanthanoid
Element 69: Thulium (Tm), Lanthanoid
Element 70: Ytterbium (Yb), Lanthanoid
Element 71: Lutetium (Lu), Lanthanoid
Element 72: Hafnium (Hf), Transition metal
Element 73: Tantalum (Ta), Transition metal
Element 74: Tungsten (W), Transition metal
Element 75: Rhenium (Re), Transition metal
Element 76: Osmium (Os), Transition metal
Element 77: Iridium (Ir), Transition metal
Element 78: Platinum (Pt), Transition metal
Element 79: Gold (Au), Transition metal
Element 80: Mercury (Hg), Transition metal
Element 81: Thallium (Tl), Other metal
Element 82: Lead (Pb), Other metal
Element 83: Bismuth (Bi), Other metal
Element 84: Polonium (Po), Metalloid
Element 85: Astatine (At), Halogen
Element 86: Radon (Rn), Noble gas
Element 87: Francium (Fr), Alkali metal
Element 88: Radium (Ra), Alkaline earth metal
Element 89: Actinium (Ac), Actinoid
Element 90: Thorium (Th), Actinoid
Element 91: Protactinium (Pa), Actinoid
Element 92: Uranium (U), Actinoid
Element 93: Neptunium (Np), Actinoid
Element 94: Plutonium (Pu), Actinoid
Element 95: Americium (Am), Actinoid
Element 96: Curium (Cm), Actinoid
Element 97: Berkelium (Bk), Actinoid
Element 98: Californium (Cf), Actinoid
Element 99: Einsteinium (Es), Actinoid
Element 100: Fermium (Fm), Actinoid
Element 101: Mendelevium (Md), Actinoid
Element 102: Nobelium (No), Actinoid
Element 103: Lawrencium (Lr), Actinoid
Element 104: Rutherfordium (Rf), Transition metal
Element 105: Dubnium (Db), Transition metal
Element 106: Seaborgium (Sg), Transition metal
Element 107: Bohrium (Bh), Transition metal
Element 108: Hassium (Hs), Transition metal
Element 109: Meitnerium (Mt)
Element 110: Darmstadtium (Ds)
Element 111: Roentgenium (Rg)
Element 112: Copernicium (Cn), Transition metal
Element 113: Ununtrium (Uut)
Element 114: Ununquadium (Uuq)
Element 115: Ununpentium (Uup)
Element 116: Ununhexium (Uuh)
Element 117: Ununseptium (Uus)
Element 118: Ununoctium (Uuo)
Samarium has a rhombohedral crystal structure
62Sm
Appearance
silvery white
General properties
Name, symbol, number samarium, Sm, 62
Pronunciation /səˈmɛəriəm/ sə-mair-ee-əm
Element category lanthanide
Group, period, block n/a, 6, f
Standard atomic weight 150.36
Electron configuration [Xe] 6s2 4f6
Electrons per shell 2, 8, 18, 24, 8, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 7.52 g·cm−3
Liquid density at m.p. 7.16 g·cm−3
Melting point 1345 K, 1072 °C, 1962 °F
Boiling point 2067 K, 1794 °C, 3261 °F
Heat of fusion 8.62 kJ·mol−1
Heat of vaporization 165 kJ·mol−1
Molar heat capacity 29.54 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1001 1106 1240 (1421) (1675) (2061)
Atomic properties
Oxidation states 3, 2 (mildly basic oxide)
Electronegativity 1.17 (Pauling scale)
Ionization energies 1st: 544.5 kJ·mol−1
2nd: 1070 kJ·mol−1
3rd: 2260 kJ·mol−1
Atomic radius 180 pm
Covalent radius 198±8 pm
Miscellanea
Crystal structure rhombohedral
Magnetic ordering paramagnetic[1]
Electrical resistivity (r.t.) (α, poly) 0.940 µΩ·m
Thermal conductivity 13.3 W·m−1·K−1
Thermal expansion (r.t.) (α, poly) 12.7 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2130 m·s−1
Young's modulus (α form) 49.7 GPa
Shear modulus (α form) 19.5 GPa
Bulk modulus (α form) 37.8 GPa
Poisson ratio (α form) 0.274
Vickers hardness 412 MPa
Brinell hardness 441 MPa
CAS registry number 7440-19-9
Most stable isotopes
Main article: Isotopes of samarium
iso NA half-life DM DE (MeV) DP
144Sm 3.07% 144Sm is stable with 82 neutrons
146Sm syn 1.03×108y α 2.529 142Nd
147Sm 14.99% 1.06×1011y α 2.310 143Nd
148Sm 11.24% 7×1015y α 1.986 144Nd
149Sm 13.82% 149Sm is stable with 87 neutrons
150Sm 7.38% 150Sm is stable with 88 neutrons
152Sm 26.75% 152Sm is stable with 90 neutrons
154Sm 22.75% 154Sm is stable with 92 neutrons
v ·  /səˈmɛəriəm/ sə-mair-ee-əm) is a chemical element with the symbol Sm, atomic number 62 and atomic weight 150.36. It is a moderately hard silvery metal which readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3. Compounds of samarium(II) are also known, most notably monoxide SmO, monochalcogenides SmS, SmSe and SmTe, as well as samarium(II) iodide. The last compound is a common reducing agent in chemical synthesis. Samarium has no significant biological role and is only slightly toxic.

Samarium was discovered in 1879 by the French chemist Paul Émile Lecoq de Boisbaudran and named after the mineral samarskite from which it was isolated. The mineral itself was earlier named after a Russian mine official, Colonel Vasili Samarsky-Bykhovets, who thereby became the first person to have a chemical element named after him, albeit indirectly. Although classified as a rare earth element, samarium is the 40th most abundant element in the Earth's crust and is more common than such metals as tin. Samarium occurs with 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 USA, Brazil, India, Sri Lanka and Australia; China is by far the world leader in samarium mining and production.

The major commercial application of samarium is in samarium-cobalt magnets which have permanent magnetization second only to neodymium magnets; however, samarium compounds can withstand significantly higher temperatures, above 700 °C, without losing their magnetic properties. Radioactive isotope samarium-153 is the major component of the drug samarium (153Sm) lexidronam (Quadramet) which kills cancer cells in the treatment of lung cancer, prostate cancer, breast cancer and osteosarcoma. Another isotope, samarium-149, is a strong neutron absorber and is therefore added to the control rods of nuclear reactors. It is also formed as a decay product during the reactor operation and is one of the important factors considered in the reactor design and operation. Other applications of samarium include catalysis of chemical reactions, radioactive dating and an X-ray laser.

Contents

Physical properties

Samarium is a rare earth metal having the hardness and density similar to those of zinc. With the boiling point of 1794 °C, samarium is the third most volatile lanthanide after ytterbium and europium; this property facilitates separation of samarium from the mineral ore. At ambient conditions, samarium normally assumes a trigonal structure (α form). Upon heating to 731 °C, its crystal symmetry changes into hexagonal close-packed (hcp), however the transition temperature depends on the metal purity. Further heating to 922 °C transforms the metal into a body-centered cubic (bcc) phase. Heating to 300 °C combined with compression to 40 kbar results in a double-hexagonal close-packed structure (dhcp). Applying higher pressure of the order of hundreds or thousands of kilobars induces a series of phase transformations, in particular with a tetragonal phase appearing at about 900 kbar.[2] In one study, the dhcp phase could be produced without compression, using a nonequilibrium annealing regime with a rapid temperature change between about 400 and 700 °C, confirming the transient character of this samarium phase. Also, thin films of samarium obtained by vapor deposition may contain the hcp or dhcp phases at ambient conditions.[2]

Samarium (and its sesquioxide) are paramagnetic at room temperature. Their corresponding effective magnetic moments, below 2µB, are the 3rd lowest among the lanthanides (and their oxides) after lanthanum and lutetium. The metal transforms to an antiferromagnetic state upon cooling to 14.8 K.[3][4] Individual samarium atoms can be isolated by encapsulating them into fullerene molecules.[5] They can also be doped between the C60 molecules in the fullerene solid, rendering it superconductive at temperatures below 8 K.[6] Samarium doping of iron-based superconductors – the most recent class of high-temperature superconductors – allows to enhance their transition temperature to 56 K, which is the highest value achieved so far in this series.[7]

Chemical properties

Freshly prepared samarium has a silvery luster. In air, it slowly oxidizes at room temperature and spontaneously ignites at 150 °C.[8][9] 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 quite quickly with hot water to form samarium hydroxide:[10]

2 Sm (s) + 6 H2O (l) → 2 Sm(OH)3 (aq) + 3 H2 (g)

Samarium dissolves readily in dilute sulfuric acid to form solutions containing the yellow[11] to pale green Sm(III) ions, which exist as [Sm(OH2)9]3+ complexes:[10]

2 Sm (s) + 3 H2SO4 (aq) → 2 Sm3+ (aq) + 3 SO2−
4
(aq) + 3 H2 (g)

Samarium is one of the few lanthanides that exhibit the oxidation state +2. The Sm2+ ions are blood-red in solutions.[12]

Compounds

Oxides

The most stable oxide of samarium is the sesquioxide Sm2O3. As many other samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm2O3 is rather high (2345 °C) and therefore melting is usually achieved not by direct heating, but with induction heating, through a radio-frequency coil. The Sm2O3 crystals of monoclinic symmetry can be grown by the flame fusion method (Verneuil process) from the Sm2O3 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 Sm2O3 to 1900 °C converts it to the more stable monoclinic phase.[15] Cubic Sm2O3 has also been described.[16]

Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm2O3 with samarium metal at elevated temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in an incomplete reaction. SmO has the cubic rock-salt lattice structure.[14][34]

Chalcogenides

Samarium forms trivalent sulfide, selenide and telluride. Divalent chalcogenides SmS, SmSe and SmTe with cubic rock-salt crystal structure are also known. They are remarkable by converting from semiconducting to metallic state at room temperature upon application of pressure. Whereas the transition is continuous and occurs at about 20–30 kbar in SmSe and SmTe, it is abrupt in SmS and requires only 6.5 kbar. This effect results in spectacular color change in SmS from black to golden yellow when its crystals of films are scratched or polished. The transition does not change lattice symmetry, but there is a sharp decrease (~15%) in the crystal volume.[35] It shows hysteresis, that is when the pressure is released, SmS returns to the semiconducting state at much lower pressure of about 0.4 kbar.[8][36]

Halides

Samarium metal reacts with all the halogens X = F, Cl, Br or I, forming trihalides:[37]

2 Sm (s) + 3 X2 (g) → 2 SmX3 (s)

Their further reduction with samarium, lithium or sodium metals at elevated temperatures (about 700–900 °C) yields dihalides.[27] The diiodide can also be prepared by heating SmI3, or by reacting the metal with 1,2-diiodoethane in anhydrous tetrahydrofuran at room temperature:[38]

Sm (s) + ICH2-CH2I → SmI2 + CH2=CH2

In addition to dihalides, the reduction also produces numerous non-stoichiometric samarium halides with a well-defined crystal structure, such as Sm3F7, Sm14F33, Sm27F64,[26] Sm11Br24, Sm5Br11 and Sm6Br13[39]

As reflected in the table above, samarium halides change their crystal structures when one type of halide atoms 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 PbCl2-type orthorhombic structure (density 5.90 g/cm3),[40] and similar treatment results in a new phase of samarium triiodide (density 5.97 g/cm3).[41]

Borides

Sintering powders of samarium oxide and boron, in vacuum, yields a powder containing several samarium boride phases, and their volume ratio can be controlled through the mixing proportion.[42] The powder can be converted into larger crystals of a certain samarium boride using arc melting or zone melting techniques, relying on the different melting/crystallization temperature of SmB6 (2580 °C), SmB4 (about 2300 °C) and SmB66 (2150 °C). All these materials are hard, brittle, dark-gray solids with the hardness increasing with the boron content.[22] Samarium diboride is too volatile to be produced with these methods and requires high pressure (about 65 kbar) and low temperatures between 1140 and 1240 °C to stabilize its growth. Increasing the temperature results in the preferential formations of SmB6.[20]

Samarium hexaboride is a typical intermediate-valence compound where samarium is present both as Sm2+ and Sm3+ ions at the ratio 3:7.[42] It belongs to a class of Kondo insulators, that is at high temperatures (above 50 K), its properties are typical of a Kondo metal, with metallic electrical conductivity characterized by strong electron scattering, whereas at low temperatures, it behaves as a non-magnetic insulator with a narrow band gap of about 4–14 meV.[43] The cooling-induced metal-insulator transition in SmB6 is accompanied by a sharp increase in the thermal conductivity, peaking at about 15 K. The reason for this increase is that electrons themselves do not contribute to the thermal conductivity at low temperatures, which is dominated by phonons, but the decrease in electron concentration reduced the rate of electron-phonon scattering.[44]

Other inorganic compounds

Samarium sulfate, Sm2(SO4)3

Samarium carbides are prepared by melting a graphite-metal mixture in an inert atmosphere. After the synthesis, they are unstable in air and are studied also under inert atmosphere.[24] Samarium monophosphide SmP is a semiconductor with the bandgap of 1.10 eV, the same as in silicon, and high electrical conductivity of n-type. It can be prepared by annealing at 1100 °C 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 °C/min.[32] Similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at 1800 °C.[33]

A large number of crystalline binary compounds are known for samarium and one of the group-4, 5 or 6 element 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 SmaXb, where the b/a ratio varies between 0.5 and 3.[45][46][47]

Organometallic compounds

Samarium forms a cyclopentadienide Sm(C5H5)3 and its chloroderivatives Sm(C5H5)2Cl and Sm(C5H5)Cl2. They are prepared by reacting samarium trichloride with NaC5H5 in tetrahydrofuran. Contrary to cyclopentadienides of most other lanthanides, in Sm(C5H5)3 some C5H5 rings bridge each other by forming ring vertexes η1 or edges η2 toward another neighboring samarium atom, thereby creating polymeric chains.[12] The chloroderivative Sm(C5H5)2Cl has a dimer structure which is more accurately expressed as (η5-C5H5)2Sm(µ-Cl)25-C5H5)2. There, the chlorine bridges can be replaced, for instance, by iodine, hydrogen or nitrogen atoms or by CN groups.[48]

The (C5H5) ion in samarium cyclopentadienides can be replaced by the indenide (C9H7) or cyclooctatetraenide (C8H8)2– ring, resulting in Sm(C9H7)3 or KSm(η8-C8H8)2. The latter compound has a similar structure to that of uranocene. There is also a cyclopentadienide of divalent samarium, Sm(C5H5)2 – a solid which sublimates at about 85 °C. Contrary to ferrocene, the C5H5 rings in Sm(C5H5)2 are not parallel but are tilted by 40°.[48][49]

Alkyls and aryls of samarium are obtained through a metathesis reaction in tetrahydrofuran or ether:[48]

SmCl3 + 3 LiR → SmR3 + 3 LiCl
Sm(OR)3 + 3 LiCH(SiMe3)2 → Sm{CH(SiMe3)2}3 + 3 LiOR

Here R is a hydrocarbon group and Me stands for methyl.

Isotopes

Naturally occurring samarium has a radioactivity of 128 Bq/g. It is composed of four stable isotopes: 144Sm, 150Sm, 152Sm and 154Sm, and three extremely long-lived radioisotopes, 147Sm (half-life t½ = 1.06×1011 years), 148Sm (7×1015 years) and 149Sm (>2×1015 years), with 152Sm being the most abundant (natural abundance 26.75%).[50] 149Sm is listed by various sources either as stable[50][51] or radioactive isotope.[52]

The long-lived isotopes,146Sm, 147Sm, and 148Sm, primarily decay by emission of alpha particles to isotopes of neodymium. Lighter unstable isotopes of samarium primarily decay by electron capture to isotopes of promethium, while heavier ones convert through beta decay to isotopes of europium.[50]

The alpha-decay of 147Sm to 143Nd with a half-life of 1.06×1011 years serve for samarium-neodymium dating

The half-lives of 151Sm and 145Sm are 90 years and 340 days, respectively. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. Samarium also has five nuclear isomers with the most stable being 141mSm (half-life 22.6 minutes), 143m1Sm (t½ = 66 seconds) and 139mSm (t½ = 10.7 seconds).[50]

History

Paul Émile Lecoq de Boisbaudran, the discoverer of samarium

Detection of samarium and related elements was announced by several scientists in the second half of the 19th century; however, most sources give the priority to the French chemist Paul Émile Lecoq de Boisbaudran.[53][54] Boisbaudran isolated samarium oxide and/or hydroxide in Paris in 1879 from the mineral samarskite ((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16) and identified a new element in it via sharp optical absorption lines.[9] The Swiss chemist Marc Delafontaine announced a new element decipium (from Latin: decipiens meaning "deceptive, misleading") in 1878,[55][56] but later in 1880–1881 demonstrated that it was a mixture of several elements, one being identical to the Boisbaudran's samarium.[57][58] Although samarskite was first found in the remote Russian region of Urals, by the late 1870s its deposits had been located in other places making the mineral available to many researchers. In particular, it was found that the samarium isolated by Boisbaudran was also impure and contained comparable amount of europium. The pure element was produced only in 1901 by Eugène-Anatole Demarçay.[59]

Boisbaudran named his element samaria after the mineral samarskite, which in turn honored Vasili Samarsky-Bykhovets (1803–1870). Samarsky-Bykhovets was the Chief of Staff of the Russian Corps of Mining Engineers who granted access for the German mineralogists, brothers Gustav Rose and Heinrich Rose, to study the mineral samples from the Urals.[60][61][62] In this sense samarium was the first chemical element to be named after a person.[59][63] Later the name samaria used by Boisbaudran was transformed into samarium, to conform with other element names, and samaria nowadays is sometimes used to refer to samarium oxide, by analogy with yttria, zirconia, alumina, ceria, holmia, etc. The symbol Sm was suggested for samarium; however an alternative Sa was frequently used instead until the 1920s.[59][64]

Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form. However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rods in some of the early nuclear reactors. Nowadays, a similar commodity product has the name "samarium-europium-gadolinium" (SEG) concentrate.[63] It is prepared by solvent extraction from the mixed lanthanides isolated from bastnäsite (or monazite). Since the heavier lanthanides have the greater 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 large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium content of the ore is rescued for use in phosphor manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.[65]

Occurrence and production

Samarskite

With the average concentration of about 8 parts per million (ppm), samarium is the 40th most abundant element in the Earth's crust. It is the fifth most abundant lanthanide and is more common than such element as tin. Samarium concentration in soils varies between 2 and 23 ppm, and oceans contain about 0.5–0.8 parts per trillion.[8] 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.[66]

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%)[9] and bastnäsite are mostly used as commercial sources. World resources of samarium are estimated at two million tonnes; they are mostly located in China, US, Brazil, India, Sri Lanka and Australia, and the annual production is about 700 tonnes.[8] 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 tonnes)[66] and India (2,700 tonnes).[67] Samarium is usually sold as oxide, which at the price of about 30 USD/kg is one of the cheapest lanthanide oxides.[65] 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 °C) and lanthanum (b. p. 3464 °C).[54]

Samarium-151 is produced in nuclear fission of uranium with the yield of about 0.4% of the total number of fission events. It is also synthesized upon neutron capture by samarium-149, which is added to the control rods of nuclear reactors. Consequently, samarium-151 is present in spent nuclear fuel and radioactive waste.[66]

Applications

Barbier reaction using SmI2

One of the most important applications of samarium is in samarium-cobalt magnets, which have a nominal composition of SmCo5 or Sm2Co17. They have high permanent magnetization, which is about 10,000 times that of iron and is second only to that of neodymium magnets. However, samarium-based magnets have higher resistance to demagnetization, as they are stable to temperatures above 700 °C (cf. 300–400 °C for neodymium magnets). These magnets are found in small motors, headphones, high-end magnetic pickups for guitars and related musical instruments.[8] For example, they are used in the motors of a solar-powered electric aircraft Solar Challenger and in the Samarium Cobalt Noiseless electric guitar and bass pickups.

Another important application of samarium and its compounds is as catalyst and chemical reagent. Samarium catalysts assist decomposition of plastics, dechlorination of pollutants such as polychlorinated biphenyls (PCBs), as well as the dehydration and dehydrogenation of ethanol.[9] Samarium(III) triflate (Sm(OTf)3, that is Sm(CF3SO3)3) is one of the most efficient Lewis acid catalysts for a halogen-promoted Friedel–Crafts reaction with alkenes.[68] Samarium(II) iodide is a very common reducing and coupling agent in organic synthesis, for example in the desulfonylation reactions; annulation; Danishefsky, Kuwajima, Mukaiyama and Holton Taxol total syntheses; strychnine total synthesis; Barbier reaction and other reductions with samarium(II) iodide.[69]

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 "flint" ignition device of many lighters and torches.[8][9]

Chemical structure of Sm-EDTMP

Radioactive samarium-153 is a beta emitter with a half-life of 46.3 hours. It is used to kill cancer cells in the treatment of lung cancer, prostate cancer, breast cancer and osteosarcoma. For this purpose, samarium-153 is 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.[8] The corresponding drug has several names including samarium (153Sm) lexidronam and its trade name is Quadramet.[70][71][72]

Samarium-149 has high cross-section for neutron capture (41,000 barns) and is therefore used in the control rods of nuclear reactors. Its advantage compared to competing materials, such as boron and cadmium, is stability of absorption – most of the fusion and decay products of samarium-149 are other isotopes of samarium which are also good neutron absorbers. For example, the cross sections of samarium-151 is 15,000 barns, it is on the order of hundred barns for samarium-150, 152, 153, and is 6,800 barns for natural (mixed-isotope) samarium.[9][66][73] Among the decay products in a nuclear reactor, samarium-149 is regarded as the second most important for the reactor design and operation after xenon-135.[74]

Non-commercial and potential applications

Samarium-doped calcium fluoride crystals were used as an active medium in one of the first solid-state lasers designed and constructed by Peter Sorokin (co-inventor of the dye laser) and Mirek Stevenson at IBM research labs in early 1961. This samarium laser emitted pulses of red light at 708.5 nm. It had to be cooled by liquid helium and thus did not find practical applications.[75][76]

Another samarium-based laser became the first saturated X-ray laser operating at wavelengths shorter than 10 nanometers. It provided 50-picosecond pulses at 7.3 and 6.8 nm suitable for applications 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 mJ. The active medium was samarium plasma produced by irradiating samarium-coated glass with a pulsed infrared Nd-glass laser (wavelength ~1.05 µm).[77]

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,[78] and such devices are being developed commercially.[79] Samarium monosulfide also generates electric voltage upon moderate heating to about 150 °C that can be applied in thermoelectric power converters.[80]

The analysis of relative concentrations of samarium and neodymium isotopes 147Sm, 144Nd and 143Nd allows the determination of the age and origin of rocks and meteorites in samarium-neodymium dating. Both elements are lanthanides and have very similar physical and chemical properties. Therefore, Sm-Nd dating is either insensitive to partitioning of the marker elements during various geological processes, or such partitioning can well be understood and modeled from the ionic radii of the involved elements.[81]

Health issues

Samarium metal has no biological role in human body. Its salts stimulate metabolism, but it is unclear whether this is the effect of samarium or other lanthanides present with it. The total amount of samarium in adults is about 50 micrograms, mostly in liver and kidneys and with about 8 micrograms per liter being dissolved in the blood. Samarium is not absorbed by plants to a measurable concentration and therefore is normally not a 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.[8]

When ingested, only about 0.05% of samarium salts is absorbed into the bloodstream and the remainder is excreted. From the blood, about 45% goes to the liver and 45% is deposited on the surface of the bones where it remains for about 10 years; the balance 10% is excreted.[66]

References

  1. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  2. ^ a b c d Shi, N; Fort, D (1985). "Preparation of samarium in the double hexagonal close packed form". Journal of the Less Common Metals 113 (2): 21. doi:10.1016/0022-5088(85)90294-2. 
  3. ^ Lock, J M (1957). "The Magnetic Susceptibilities of Lanthanum, Cerium, Praseodymium, Neodymium and Samarium, from 1.5 K to 300 K". Proceedings of the Physical Society. Section B 70 (6): 566. Bibcode 1957PPSB...70..566L. doi:10.1088/0370-1301/70/6/304. 
  4. ^ Huray, P; Nave, S; Haire, R (1983). "Magnetism of the heavy 5f elements". Journal of the Less Common Metals 93 (2): 293. doi:10.1016/0022-5088(83)90175-3. 
  5. ^ Okazaki, T (2002). "Electronic and geometric structures of metallofullerene peapods". Physica B 323: 97. Bibcode 2002PhyB..323...97O. doi:10.1016/S0921-4526(02)00991-2. 
  6. ^ Chen, X.; Roth, G. (1995). "Superconductivity at 8 K in samarium-doped C60". Physical Review B 52 (21): 15534. Bibcode 1995PhRvB..5215534C. doi:10.1103/PhysRevB.52.15534. 
  7. ^ Wu, G. et al. (2008). "Superconductivity at 56 K in Samarium-doped SrFeAsF". Journal of Physics: Condensed Matter 21 (14): 142203. arXiv:0811.0761. Bibcode 2009JPCM...21n2203W. doi:10.1088/0953-8984/21/14/142203. 
  8. ^ a b c d e f g h Emsley, John (2001). "Samarium". Nature's Building Blocks: An A-Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 371–374. ISBN 0198503407. http://books.google.com/?id=j-Xu07p3cKwC&pg=PA371. 
  9. ^ a b c d e f C. R. Hammond. The Elements, in Handbook of Chemistry and Physics 81st edition. CRC press. ISBN 0849304857. 
  10. ^ a b "Chemical reactions of Samarium". Webelements. https://www.webelements.com/samarium/chemistry.html. Retrieved 2009-06-06. 
  11. ^ Greenwood, p. 1243
  12. ^ a b Greenwood, p.1248
  13. ^ Vohra, Y (1991). "A new ultra-high pressure phase in samarium". Physics Letters A 158: 89. Bibcode 1991PhLA..158...89V. doi:10.1016/0375-9601(91)90346-A. 
  14. ^ a b Leger, J; Yacoubi, N; Loriers, J (1981). "Synthesis of rare earth monoxides". Journal of Solid State Chemistry 36 (3): 261. Bibcode 1981JSSCh..36..261L. doi:10.1016/0022-4596(81)90436-9. 
  15. ^ a b c Gouteron, J (1981). "Raman spectra of lanthanide sesquioxide single crystals: Correlation between A and B-type structures". Journal of Solid State Chemistry 38 (3): 288. Bibcode 1981JSSCh..38..288G. doi:10.1016/0022-4596(81)90058-X. 
  16. ^ a b Taylor D. (1984). Br. Ceram. Trans. J. 83: 92–98. 
  17. ^ Daou, J; Vajda, P; Burger, J (1989). "Low temperature thermal expansion in SmH2+x". Solid State Communications 71 (12): 1145. Bibcode 1989SSCom..71.1145D. doi:10.1016/0038-1098(89)90728-X. 
  18. ^ Dolukhanyan, S (1997). "Synthesis of novel compounds by hydrogen combustion". Journal of Alloys and Compounds 253–254: 10. doi:10.1016/S0925-8388(96)03071-X. 
  19. ^ Zavalii, L. V.; Kuz'ma, Yu. B.; Mikhalenko, S. I. (1990). "Sm2B5 boride and its structure". Soviet Powder Metallurgy and Metal Ceramics 29 (6): 471. doi:10.1007/BF00795346. 
  20. ^ a b Cannon, J; Cannon, D; Tracyhall, H (1977). "High pressure syntheses of SmB2 and GdB12". Journal of the Less Common Metals 56: 83. doi:10.1016/0022-5088(77)90221-1. 
  21. ^ Etourneau, J; Mercurio, J; Berrada, A; Hagenmuller, P; Georges, R; Bourezg, R; Gianduzzo, J (1979). "The magnetic and electrical properties of some rare earth tetraborides". Journal of the Less Common Metals 67 (2): 531. doi:10.1016/0022-5088(79)90038-9. 
  22. ^ a b Solovyev, G. I.; Spear, K. E. (1972). "Phase Behavior in the Sm-B System". Journal of the American Ceramic Society 55 (9): 475. doi:10.1111/j.1151-2916.1972.tb11344.x. 
  23. ^ Schwetz, K; Ettmayer, P; Kieffer, R; Lipp, A (1972). "Über die Hektoboridphasen der Lanthaniden und Aktiniden". Journal of the Less Common Metals 26: 99. doi:10.1016/0022-5088(72)90012-4. 
  24. ^ a b c Spedding, F. H.; Gschneidner, K.; Daane, A. H. (1958). "The Crystal Structures of Some of the Rare Earth Carbides". Journal of the American Chemical Society 80 (17): 4499. doi:10.1021/ja01550a017. 
  25. ^ a b c d e f g h Greenwood, p. 1241
  26. ^ a b c d Greis, O (1978). "Über neue Verbindungen im system SmF2_SmF3". Journal of Solid State Chemistry 24 (2): 227. Bibcode 1978JSSCh..24..227G. doi:10.1016/0022-4596(78)90013-0. 
  27. ^ a b Meyer, G; Schleid, T (1986). "The metallothermic reduction of several rare-earth trichlorides with lithium and sodium". Journal of the Less Common Metals 116: 187. doi:10.1016/0022-5088(86)90228-6. 
  28. ^ Bärnighausen, H. (1973). Rev. Chim. Miner. 10: 77–92. 
  29. ^ Zachariasen, W. H. (1948). "Crystal chemical studies of the 5f-series of elements. I. New structure types". Acta Crystallographica 1 (5): 265. doi:10.1107/S0365110X48000703. 
  30. ^ Asprey, L. B.; Keenan, T. K.; Kruse, F. H. (1964). Inorganic Chemistry 3 (8): 1137. doi:10.1021/ic50018a015. 
  31. ^ Brown, R (1974). "Composition limits and vaporization behaviour of rare earth nitrides". Journal of Inorganic and Nuclear Chemistry 36 (11): 2507. doi:10.1016/0022-1902(74)80462-8. 
  32. ^ a b Meng, J (1991). "Studies on the electrical properties of rare earth monophosphides". Journal of Solid State Chemistry 95 (2): 346. Bibcode 1991JSSCh..95..346M. doi:10.1016/0022-4596(91)90115-X. 
  33. ^ a b Beeken, R.; Schweitzer, J. (1981). "Intermediate valence in alloys of SmSe with SmAs". Physical Review B 23 (8): 3620. Bibcode 1981PhRvB..23.3620B. doi:10.1103/PhysRevB.23.3620. 
  34. ^ Greenwood, p. 1239
  35. ^ Beaurepaire, Eric (Ed.) Magnetism: a synchrotron radiation approach, Springer, 2006 ISBN 3540332413 p. 393
  36. ^ Jayaraman, A.; Narayanamurti, V.; Bucher, E.; Maines, R. (1970). "Continuous and Discontinuous Semiconductor-Metal Transition in Samarium Monochalcogenides Under Pressure". Physical Review Letters 25 (20): 1430. Bibcode 1970PhRvL..25.1430J. doi:10.1103/PhysRevLett.25.1430. 
  37. ^ Greenwood, pp. 1236, 1241
  38. ^ Greenwood, p. 1240
  39. ^ Baernighausen, H.; Haschke, John M. (1978). "Compositions and crystal structures of the intermediate phases in the samarium-bromine system". Inorganic Chemistry 17: 18. doi:10.1021/ic50179a005. 
  40. ^ Beck, H. P. (1979). "Hochdruckmodifikationen der Diiodide von Sr, Sm und Eu. Eine neue PbCl2-Variante?". Zeitschrift für anorganische und allgemeine Chemie 459: 81. doi:10.1002/zaac.19794590108. 
  41. ^ Beck, H. P.; Gladrow, E. (1979). "Zur Hochdruckpolymorphie der Seltenerd-Trihalogenide". Zeitschrift für anorganische und allgemeine Chemie 453: 79. doi:10.1002/zaac.19794530610. 
  42. ^ a b Nickerson, J.; White, R.; Lee, K.; Bachmann, R.; Geballe, T.; Hull, G. (1971). "Physical Properties of SmB6". Physical Review B 3 (6): 2030. Bibcode 1971PhRvB...3.2030N. doi:10.1103/PhysRevB.3.2030. 
  43. ^ Nyhus, P.; Cooper, S.; Fisk, Z.; Sarrao, J. (1995). "Light scattering from gap excitations and bound states in SmB6". Physical Review B 52 (20): R14308. Bibcode 1995PhRvB..5214308N. doi:10.1103/PhysRevB.52.R14308. 
  44. ^ Sera, M.; Kobayashi, S.; Hiroi, M.; Kobayashi, N.; Kunii, S. (1996). "Thermal conductivity of RB6 (R=Ce,Pr,Nd,Sm,Gd) single crystals". Physical Review B 54 (8): R5207. Bibcode 1996PhRvB..54.5207S. doi:10.1103/PhysRevB.54.R5207. 
  45. ^ Gladyshevskii, E. I.; Kripyakevich, P. I. (1965). "Monosilicides of rare earth metals and their crystal structures". Journal of Structural Chemistry 5 (6): 789. doi:10.1007/BF00744231. 
  46. ^ Smith, G. S.; Tharp, A. G.; Johnson, W. (1967). "Rare earth–germanium and –silicon compounds at 5:4 and 5:3 compositions". Acta Crystallographica 22 (6): 940. doi:10.1107/S0365110X67001902. 
  47. ^ Yarembash E.I., Tyurin E.G., Reshchikova A.A., Karabekov A., Klinaeva N.N. (1971). Inorg. Mater. 7: 661–665. 
  48. ^ a b c Greenwood, p. 1249
  49. ^ Evans, William J.; Hughes, Laura A.; Hanusa, Timothy P. (1986). "Synthesis and x-ray crystal structure of bis(pentamethylcyclopentadienyl) complexes of samarium and europium: (C5Me5)2Sm and (C5Me5)2Eu". Organometallics 5 (7): 1285. doi:10.1021/om00138a001. 
  50. ^ a b c d Audi, G (2003). "The NUBASE evaluation of nuclear and decay properties". Nuclear Physics A 729: 3. Bibcode 2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf. 
  51. ^ Chart of the nuclides, Brookhaven National Laboratory
  52. ^ Holden, Norman E. "Table of the isotopes" in Lide, D. R., ed (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. 
  53. ^ Greenwood, p. 1229
  54. ^ a b Samarium, Encyclopedia Britannica on-line
  55. ^ Delafontaine, Marc (1878). "Sur le décepium, métal nouveau de la samarskite". Journal de pharmacie et de chimie 28: 540. http://gallica.bnf.fr/ark:/12148/bpt6k78100m.image.r=Decipium.f548.langEN. 
  56. ^ Delafontaine, Marc (1878). "Sur le décepium, métal nouveau de la samarskite". Comptes rendus hebdomadaires 87: 632. http://gallica.bnf.fr/ark:/12148/bpt6k3044x.image.r=Decipium.f694.langEN. 
  57. ^ De Laeter, J. R.; Böhlke, J. K.; De Bièvre, P.; Hidaka, H.; Peiser, H. S.; Rosman, K. J. R.; Taylor, P. D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry (IUPAC) 75 (6): 683–800. doi:10.1351/pac200375060683. 
  58. ^ Delafontaine, Marc (1881). "Sur le décipium et le samarium". Comptes rendus hebdomadaires 93: 63. http://gallica.bnf.fr/ark:/12148/bpt6k3049g.image.r=Decipium.f63.langEN. 
  59. ^ a b c Samarium: History & Etymology
  60. ^ Samarskite, Great Soviet Encyclopedia (in Russian)
  61. ^ Boisbaudran, Lecoq de (1879). "Recherches sur le samarium, radical d'une terre nouvelle extraite de la samarskite". Comptes rendus hebdomadaires des seances de l'Academie des sciences 89: 212–214. http://gallica.bnf.fr/ark:/12148/bpt6k3046j/f214.pagination. 
  62. ^ Shipley, Joseph Twadell. The Origins of English Words: A Discursive Dictionary of Indo-European Roots, JHU Press, 2001, p.90. ISBN 0801867843
  63. ^ a b Chemistry in Its Element – Samarium, Royal Society of Chemistry
  64. ^ Coplen, T. B.; Peiser, H. S. (1998). "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)". Pure and Applied Chemistry 70: 237. doi:10.1351/pac199870010237. 
  65. ^ a b What are their prices?, Lynas corp.
  66. ^ a b c d e Human Health Fact Sheet on Samarium, Los Alamos National Laboratory
  67. ^ "Rare Earths". United States Geological Surves. 2010-01. http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/mcs-2010-raree.pdf. Retrieved 2010-12-10. 
  68. ^ S. Hajra, B. Maji and S. Bar (2007). "Samarium Triflate-Catalyzed Halogen-Promoted Friedel-Crafts Alkylation with Alkenes". Org. Lett. 9 (15): 2783–2786. doi:10.1021/ol070813t. 
  69. ^ Cotton (2007). Advanced inorganic chemistry, 6th ed. Wiley-India. p. 1128. ISBN 8126513381. http://books.google.com/?id=U3MWRONWAmMC&pg=PA1128. 
  70. ^ "Centerwatch About drug Quadramet". http://www.centerwatch.com/patient/drugs/dru267.html. Retrieved 2009-06-06. 
  71. ^ Pattison, JE (1999). "Finger doses received during 153Sm injections". Health physics 77 (5): 530–5. doi:10.1097/00004032-199911000-00006. PMID 10524506. 
  72. ^ Finlay, IG; Mason, MD; Shelley, M (2005). "Radioisotopes for the palliation of metastatic bone cancer: a systematic review". The lancet oncology 6 (6): 392–400. doi:10.1016/S1470-2045(05)70206-0. PMID 15925817. 
  73. ^ Thermal neutron capture cross sections and resonance integrals – Fission product nuclear data
  74. ^ DOE Fundamentals Handbook: Nuclear Physics and Reactor Theory. U.S. Department of Energy. January 1993. pp. 34, 67. http://www.hss.energy.gov/nuclearsafety/ns/techstds/standard/hdbk1019/h1019v2.pdf. 
  75. ^ Robert Bud, Philip Gummett Cold War, Hot Science: Applied Research in Britain's Defence Laboratories, 1945–1990, NMSI Trading Ltd, 2002 ISBN 1900747472 p. 268
  76. ^ Sorokin, P. P. (1979). "Contributions of IBM to Laser Science—1960 to the Present". IBM Journal of Research and Development 23 (5): 476. doi:10.1147/rd.235.0476. 
  77. ^ Zhang, J. (1997). "A Saturated X-ray Laser Beam at 7 Nanometers". Science 276 (5315): 1097. doi:10.1126/science.276.5315.1097. 
  78. ^ Elmegreen, Bruce G. et al. Piezo-driven non-volatile memory cell with hysteretic resistance US patent application 12/234100, 09/19/2008
  79. ^ SmS Tenzo
  80. ^ Kaminskii, V. V.; Solov’ev, S. M.; Golubkov, A. V. (2002). "Electromotive Force Generation in Homogeneously Heated Semiconducting Samarium Monosulfide". Technical Physics Letters 28 (3): 229. Bibcode 2002TePhL..28..229K. doi:10.1134/1.1467284. http://www.tenzo-sms.ru/en/articles/5.  other articles on this topic
  81. ^ Robert Bowen, H -G Attendorn Isotopes in the Earth Sciences, Springer, 1988, ISBN 0412537109, pp. 270 ff

Bibliography

  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 

External links