Dysprosium

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Dysprosium,  66Dy
Dy chips.jpg
General properties
Name, symbol dysprosium, Dy
Pronunciation dis-PROH-zee-əm
Appearance silvery white
Dysprosium in the periodic table
Hydrogen (diatomic nonmetal)
Helium (noble gas)
Lithium (alkali metal)
Beryllium (alkaline earth metal)
Boron (metalloid)
Carbon (polyatomic nonmetal)
Nitrogen (diatomic nonmetal)
Oxygen (diatomic nonmetal)
Fluorine (diatomic nonmetal)
Neon (noble gas)
Sodium (alkali metal)
Magnesium (alkaline earth metal)
Aluminium (post-transition metal)
Silicon (metalloid)
Phosphorus (polyatomic nonmetal)
Sulfur (polyatomic nonmetal)
Chlorine (diatomic nonmetal)
Argon (noble gas)
Potassium (alkali metal)
Calcium (alkaline earth metal)
Scandium (transition metal)
Titanium (transition metal)
Vanadium (transition metal)
Chromium (transition metal)
Manganese (transition metal)
Iron (transition metal)
Cobalt (transition metal)
Nickel (transition metal)
Copper (transition metal)
Zinc (transition metal)
Gallium (post-transition metal)
Germanium (metalloid)
Arsenic (metalloid)
Selenium (polyatomic nonmetal)
Bromine (diatomic nonmetal)
Krypton (noble gas)
Rubidium (alkali metal)
Strontium (alkaline earth metal)
Yttrium (transition metal)
Zirconium (transition metal)
Niobium (transition metal)
Molybdenum (transition metal)
Technetium (transition metal)
Ruthenium (transition metal)
Rhodium (transition metal)
Palladium (transition metal)
Silver (transition metal)
Cadmium (transition metal)
Indium (post-transition metal)
Tin (post-transition metal)
Antimony (metalloid)
Tellurium (metalloid)
Iodine (diatomic nonmetal)
Xenon (noble gas)
Caesium (alkali metal)
Barium (alkaline earth metal)
Lanthanum (lanthanide)
Cerium (lanthanide)
Praseodymium (lanthanide)
Neodymium (lanthanide)
Promethium (lanthanide)
Samarium (lanthanide)
Europium (lanthanide)
Gadolinium (lanthanide)
Terbium (lanthanide)
Dysprosium (lanthanide)
Holmium (lanthanide)
Erbium (lanthanide)
Thulium (lanthanide)
Ytterbium (lanthanide)
Lutetium (lanthanide)
Hafnium (transition metal)
Tantalum (transition metal)
Tungsten (transition metal)
Rhenium (transition metal)
Osmium (transition metal)
Iridium (transition metal)
Platinum (transition metal)
Gold (transition metal)
Mercury (transition metal)
Thallium (post-transition metal)
Lead (post-transition metal)
Bismuth (post-transition metal)
Polonium (post-transition metal)
Astatine (metalloid)
Radon (noble gas)
Francium (alkali metal)
Radium (alkaline earth metal)
Actinium (actinide)
Thorium (actinide)
Protactinium (actinide)
Uranium (actinide)
Neptunium (actinide)
Plutonium (actinide)
Americium (actinide)
Curium (actinide)
Berkelium (actinide)
Californium (actinide)
Einsteinium (actinide)
Fermium (actinide)
Mendelevium (actinide)
Nobelium (actinide)
Lawrencium (actinide)
Rutherfordium (transition metal)
Dubnium (transition metal)
Seaborgium (transition metal)
Bohrium (transition metal)
Hassium (transition metal)
Meitnerium (unknown chemical properties)
Darmstadtium (unknown chemical properties)
Roentgenium (unknown chemical properties)
Copernicium (transition metal)
Ununtrium (unknown chemical properties)
Flerovium (post-transition metal)
Ununpentium (unknown chemical properties)
Livermorium (unknown chemical properties)
Ununseptium (unknown chemical properties)
Ununoctium (unknown chemical properties)


Dy

Cf
terbiumdysprosiumholmium
Atomic number 66
Standard atomic weight 162.500(1)
Element category lanthanide
Group, block group n/a, f-block
Period period 6
Electron configuration [Xe] 4f10 6s2
per shell 2, 8, 18, 28, 8, 2
Physical properties
Phase solid
Melting point 1680 K ​(1407 °C, ​2565 °F)
Boiling point 2840 K ​(2562 °C, ​4653 °F)
Density (near r.t.) 8.540 g·cm−3 (at 0 °C, 101.325 kPa)
Liquid density at m.p.: 8.37 g·cm−3
Heat of fusion 11.06 kJ·mol−1
Heat of vaporization 280 kJ·mol−1
Molar heat capacity 27.7 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1378 1523 (1704) (1954) (2304) (2831)
Atomic properties
Oxidation states 3, 2, 1 ​(a weakly basic oxide)
Electronegativity 1.22 (Pauling scale)
Ionization energies 1st: 573.0 kJ·mol−1
2nd: 1130 kJ·mol−1
3rd: 2200 kJ·mol−1
Atomic radius empirical: 178 pm
Covalent radius 192±7 pm
Miscellanea
Crystal structure hexagonal close-packed (hcp)
Hexagonal close packed crystal structure for dysprosium
Speed of sound thin rod: 2710 m·s−1 (at 20 °C)
Thermal expansion α, poly: 9.9 µm·m−1·K−1 (r.t.)
Thermal conductivity 10.7 W·m−1·K−1
Electrical resistivity α, poly: 926 nΩ·m (r.t.)
Magnetic ordering paramagnetic at 300 K
Young's modulus α form: 61.4 GPa
Shear modulus α form: 24.7 GPa
Bulk modulus α form: 40.5 GPa
Poisson ratio α form: 0.247
Vickers hardness 540 MPa
Brinell hardness 500 MPa
CAS number 7429-91-6
History
Discovery Lecoq de Boisbaudran (1886)
Most stable isotopes
Main article: Isotopes of dysprosium
iso NA half-life DM DE (MeV) DP
154Dy syn 3.0×106 y α 2.947 150Gd
156Dy 0.06% >1×1018 y (α) 1.7579 152Gd
(β+β+) 2.0108 156Gd
158Dy 0.10% (α) 0.8748 154Gd
+β+) 0.2833 158Gd
160Dy 2.34% (α) 0.4387 156Gd
161Dy 18.91% (α) 0.3443 157Gd
162Dy 25.51% (α) 0.0847 158Gd
163Dy 24.90% (SF) <79.055
164Dy 28.18% (SF) <79.499
Decay modes in parentheses are predicted, but have not yet been observed
· references

Dysprosium is a chemical element with symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime. Naturally occurring dysprosium is composed of 7 isotopes, the most abundant of which is 164Dy.

Dysprosium was first identified in 1886 by Paul Émile Lecoq de Boisbaudran, but was not isolated in pure form until the development of ion exchange techniques in the 1950s. Dysprosium is used for its high thermal neutron absorption cross-section in making control rods in nuclear reactors, for its high magnetic susceptibility in data storage applications, and as a component of Terfenol-D. Soluble dysprosium salts are mildly toxic, while the insoluble salts are considered non-toxic.

Characteristics[edit]

Physical properties[edit]

Dysprosium sample

Dysprosium is a rare earth element that has a metallic, bright silver luster. It is soft enough to be cut with a knife, and can be machined without sparking if overheating is avoided. Dysprosium's physical characteristics can be greatly affected even by small amounts of impurities.[1]

Dysprosium and holmium have the highest magnetic strengths of the elements,[2] especially at low temperatures.[3] Dysprosium has a simple ferromagnetic ordering at temperatures below 85 K (−188.2 °C). Above 85 K (−188.2 °C), it turns into an helical antiferromagnetic state in which all of the atomic moments in a particular basal plane layer are parallel, and oriented at a fixed angle to the moments of adjacent layers. This unusual antiferromagnetism transforms into a disordered (paramagnetic) state at 179 K (−94 °C).[4]

Chemical properties[edit]

Dysprosium metal tarnishes slowly in air and burns readily to form dysprosium(III) oxide:

4 Dy + 3 O2 → 2 Dy2O3

Dysprosium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form dysprosium hydroxide:

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

Dysprosium metal vigorously reacts with all the halogens at above 200 °C:

2 Dy (s) + 3 F2 (g) → 2 DyF3 (s) [green]
2 Dy (s) + 3 Cl2 (g) → 2 DyCl3 (s) [white]
2 Dy (s) + 3 Br2 (g) → 2 DyBr3 (s) [white]
2 Dy (s) + 3 I2 (g) → 2 DyI3 (s) [green]

Dysprosium dissolves readily in dilute sulfuric acid to form solutions containing the yellow Dy(III) ions, which exist as a [Dy(OH2)9]3+ complexes:[5]

2 Dy (s) + 3 H2SO4 (aq) → 2 Dy3+ (aq) + 3 SO2−
4
(aq) + 3 H2 (g)

The resulting compound, dysprosium(III) sulfate, is noticeably paramagnetic.

Compounds[edit]

Dysprosium sulfate, Dy2(SO4)3

Dysprosium halides, such as DyF3 and DyBr3, tend to take on a yellow color. Dysprosium oxide, also known as dysprosia, is a white powder that is highly magnetic, more so than iron oxide.[3]

Dysprosium combines with various non-metals at high temperatures to form binary compounds with varying composition and oxidation states +3 and sometimes +2, such as DyN, DyP, DyH2 and DyH3; DyS, DyS2, Dy2S3 and Dy5S7; DyB2, DyB4, DyB6 and DyB12, as well as Dy3C and Dy2C3.[6]

Dysprosium carbonate, Dy2(CO3)3, and dysprosium sulfate, Dy2(SO4)3, result from similar reactions.[7] Most dysprosium compounds are soluble in water, though dysprosium carbonate tetrahydrate (Dy2(CO3)3·4H2O) and dysprosium oxalate decahydrate (Dy2(C2O4)3·10H2O) are both insoluble in water.[8][9]

Isotopes[edit]

Naturally occurring dysprosium is composed of 7 isotopes: 156Dy, 158Dy, 160Dy, 161Dy, 162Dy, 163Dy, and 164Dy. These are all considered stable, although 156Dy decays by alpha decay with a half-life of over 1×1018 years. Of the naturally occurring isotopes, 164Dy is the most abundant at 28%, followed by 162Dy at 26%. The least abundant is 156Dy at 0.06%.[10]

Twenty-nine radioisotopes have also been synthesized, ranging in atomic mass from 138 to 173. The most stable of these is 154Dy with a half-life of approximately 3×106 years, followed by 159Dy with a half-life of 144.4 days. The least stable is 138Dy with a half-life of 200 ms. Isotopes that are lighter than the stable isotopes tend to decay primarily by β+ decay, while those that are heavier tend to decay by β decay, with some exceptions. 154Dy decays primarily by alpha decay, and 152Dy and 159Dy decay primarily by electron capture.[10] Dysprosium also has at least 11 metastable isomers, ranging in atomic mass from 140 to 165. The most stable of these is 165mDy, which has a half-life of 1.257 minutes. 149Dy has two metastable isomers, the second of which, 149m2Dy, has a half-life of 28 ns.[10]

History[edit]

In 1878, erbium ores were found to contain the oxides of holmium and thulium. French chemist Paul Émile Lecoq de Boisbaudran, while working with holmium oxide, separated dysprosium oxide from it in Paris in 1886.[11] His procedure for isolating the dysprosium involved dissolving dysprosium oxide in acid, then adding ammonia to precipitate the hydroxide. He was only able to isolate dysprosium from its oxide after more than 30 attempts at his procedure. Upon succeeding, he named the element dysprosium from the Greek dysprositos (δυσπρόσιτος), meaning "hard to get". However, the element was not isolated in relatively pure form until after the development of ion exchange techniques by Frank Spedding at Iowa State University in the early 1950s.[2]

In 1950, Glenn T. Seaborg, Albert Ghiorso, and Stanley G. Thompson bombarded 241Am with helium ions, which produced atoms with an atomic number of 97 and which closely resembled the neighboring lanthanide terbium. Because terbium was named after Ytterby, the city in which it and several other elements were discovered, this new element was named berkelium for the city in which it was synthesized. However, when the research team synthesized element 98, they could not think of a good analogy for dysprosium, and instead named the element californium in honor of the state in which it was synthesized. The research team went on to "point out that, in recognition of the fact that dysprosium is named on the basis of a Greek word meaning 'difficult to get at,' that the searchers for another element a century ago found it difficult to get to California."[12]

Occurrence[edit]

Xenotime

Dysprosium is never encountered as a free element, but is found in many minerals, including xenotime, fergusonite, gadolinite, euxenite, polycrase, blomstrandine, monazite and bastnäsite; often with erbium and holmium or other rare earth elements. Currently, most dysprosium is being obtained from the ion-adsorption clay ores of southern China,[13] and future sources will include the Halls Creek region in Western Australia.[14] In the high-yttrium version of these, dysprosium happens to be the most abundant of the heavy lanthanides, comprising up to 7–8% of the concentrate (as compared to about 65% for yttrium).[15][16] The concentration of Dy in the Earth crust is about 5.2 mg/kg and in sea water 0.9 ng/L.[6]

Production[edit]

Dysprosium is obtained primarily from monazite sand, a mixture of various phosphates. The metal is obtained as a by-product in the commercial extraction of yttrium. In isolating dysprosium, most of the unwanted metals can be removed magnetically or by a flotation process. Dysprosium can then be separated from other rare earth metals by an ion exchange displacement process. The resulting dysprosium ions can then react with either fluorine or chlorine to form dysprosium fluoride, DyF3, or dysprosium chloride, DyCl3. These compounds can be reduced using either calcium or lithium metals in the following reactions:[7]

3 Ca + 2 DyF3 → 2 Dy + 3 CaF2
3 Li + DyCl3 → Dy + 3 LiCl

The components are placed in a tantalum crucible and fired in a helium atmosphere. As the reaction progresses, the resulting halide compounds and molten dysprosium separate due to differences in density. When the mixture cools, the dysprosium can be cut away from the impurities.[7]

About 100 tonnes of dysprosium are produced worldwide each year,[17] with 99% of that total produced in China.[18] Dysprosium prices have climbed nearly twentyfold, from $7 per pound in 2003, to $130 a pound in late 2010.[18] According to the United States Department of Energy, the wide range of its current and projected uses, together with the lack of any immediately suitable replacement, makes dysprosium the single most critical element for emerging clean energy technologies - even their most conservative projections predict a shortfall of dysprosium before 2015.[19]

Applications[edit]

Dysprosium is used, in conjunction with vanadium and other elements, in making laser materials and commercial lighting. Because of dysprosium's high thermal neutron absorption cross-section, dysprosium oxide-nickel cermets are used in neutron-absorbing control rods in nuclear reactors.[2][20] Dysprosium-cadmium chalcogenides are sources of infrared radiation which is useful for studying chemical reactions.[1] Because dysprosium and its compounds are highly susceptible to magnetization, they are employed in various data storage applications, such as in hard disks.[21]

Neodymium-iron-boron magnets can have up to 6% of the neodymium substituted with dysprosium[22] to raise the coercivity for demanding applications such as drive motors for electric vehicles. This substitution would require up to 100 grams of dysprosium per car produced. Based on Toyota's projected 2 million units per year, the use of dysprosium in applications such as this would quickly exhaust the available supply of the metal.[23] The dysprosium substitution may also be useful in other applications, as it improves the corrosion resistance of the magnets.[24]

Dysprosium is one of the components of Terfenol-D, along with iron and terbium. Terfenol-D has the highest room-temperature magnetostriction of any known material;[25] this property is employed in transducers, wide-band mechanical resonators,[26] and high-precision liquid fuel injectors.[27]

Dysprosium is used in dosimeters for measuring ionizing radiation. Crystals of calcium sulfate or calcium fluoride are doped with dysprosium. When these crystals are exposed to radiation, the dysprosium atoms become excited and luminescent. The luminescence can be measured to determine the degree of exposure to which the dosimeter has been subjected.[2]

Nanofibers of dysprosium compounds have high strength and large surface area; therefore, they can be used for reinforcement of other materials and as a catalyst. Fibers of dysprosium oxide fluoride can be produced by heating an aqueous solution of DyBr3 and NaF to 450 °C at 450 bar pressure for 17 hours. This material is remarkably robust, surviving over 100 hours in various aqueous solutions at temperatures exceeding 400 °C without re-dissolving or aggregating.[28][29][30]

Dysprosium iodide and dysprosium bromide are used in high intensity Metal-halide lamps. These compounds dissociate near the hot center of the lamp releasing isolated dysprosium atoms. The latter re-emit light in the green and red part of the spectrum thereby effectively producing bright light.[2][31]

Several paramagnetic crystal salts of dysprosium (Dysprosium Gallium Garnet, DGG; Dysprosium Aluminum Garnet, DAG; Dysprosium Iron Garnet, DyIG) are used in Adiabatic Demagnetization Refrigerators.[32][33]

Precautions[edit]

Like many powders, dysprosium powder may present an explosion hazard when mixed with air and when an ignition source is present. Thin foils of the substance can also be ignited by sparks or by static electricity. Dysprosium fires cannot be put out by water. It can react with water to produce flammable hydrogen gas.[34] Dysprosium chloride fires, however, can be extinguished with water,[35] while dysprosium fluoride and dysprosium oxide are non-flammable.[36][37] Dysprosium nitrate, Dy(NO3)3, is a strong oxidizing agent and will readily ignite upon contact with organic substances.[3]

Soluble dysprosium salts, such as dysprosium chloride and dysprosium nitrate, are mildly toxic when ingested. The insoluble salts, however, are non-toxic. Based on the toxicity of dysprosium chloride to mice, it is estimated that the ingestion of 500 grams or more could be fatal to a human.[2]

See also[edit]

References[edit]

  1. ^ a b Lide, David R., ed. (2007–2008). "Dysprosium". CRC Handbook of Chemistry and Physics 4. New York: CRC Press. p. 11. ISBN 978-0-8493-0488-0. 
  2. ^ a b c d e f Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 129–132. ISBN 0-19-850341-5. 
  3. ^ a b c Krebs, Robert E. (1998). "Dysprosium". The History and Use of our Earth's Chemical Elements. Greenwood Press. pp. 234–235. ISBN 0-313-30123-9. 
  4. ^ Jackson, Mike (2000). "Wherefore Gadolinium? Magnetism of the Rare Earths" (PDF). IRM Quarterly (Institute for Rock Magnetism) 10 (3): 6. 
  5. ^ "Chemical reactions of Dysprosium". Webelements. Retrieved 2012-08-16. 
  6. ^ a b Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 289–290. ISBN 0-07-049439-8. Retrieved 2009-06-06. 
  7. ^ a b c Heiserman, David L. (1992). Exploring Chemical Elements and their Compounds. TAB Books. pp. 236–238. ISBN 0-8306-3018-X. 
  8. ^ Perry, D. L. (1995). Handbook of Inorganic Compounds. CRC Press. pp. 152–154. ISBN 0-8493-8671-3. 
  9. ^ Jantsch, G.; Ohl, A. (1911). "Zur Kenntnis der Verbindungen des Dysprosiums". Berichte der deutschen chemischen Gesellschaft 44 (2): 1274–1280. doi:10.1002/cber.19110440215. 
  10. ^ a b c Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A.H. (2003). "Nubase2003 Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001. 
  11. ^ Paul Émile Lecoq de Boisbaudran (1886). "L'holmine (ou terre X de M Soret) contient au moins deux radicaux métallique (Holminia contains at least two metal)". Comptes Rendus (in French) 143: 1003–1006. 
  12. ^ Weeks, M. E. (1968). Discovery of the Elements (7 ed.). Journal of Chemical Education. pp. 848–849. ISBN 0-8486-8579-2. OCLC 23991202. 
  13. ^ Bradsher, Keith (December 25, 2009). "Earth-Friendly Elements, Mined Destructively". The New York Times. 
  14. ^ Brann, Matt (November 27, 2011). "Halls Creek turning into a hub for rare earths". 
  15. ^ Naumov, A. V. (2008). "Review of the World Market of Rare-Earth Metals". Russian Journal of Non-Ferrous Metals 49 (1): 14–22. doi:10.1007/s11981-008-1004-6. 
  16. ^ Gupta, C. K.; Krishnamurthy N. (2005). Extractive Metallurgy of Rare Earths. CRC Press. ISBN 978-0-415-33340-5. 
  17. ^ "Dysprosium (Dy) - Chemical properties, Health and Environmental effects". Lenntech Water treatment & air purification Holding B.V. 2008. Retrieved 2009-06-02. 
  18. ^ a b Bradsher, Keith (December 29, 2010). "In China, Illegal Rare Earth Mines Face Crackdown". The New York Times. 
  19. ^ New Scientist, 18 June 2011, p. 40
  20. ^ Amit, Sinha; Sharma, Beant Prakash (2005). "Development of Dysprosium Titanate Based Ceramics". Journal of the American Ceramic Society 88 (4): 1064–1066. doi:10.1111/j.1551-2916.2005.00211.x. 
  21. ^ Lagowski, J. J., ed. (2004). Chemistry Foundations and Applications 2. Thomson Gale. pp. 267–268. ISBN 0-02-865724-1. 
  22. ^ Shi, Fang, X.; Shi, Y.; Jiles, D.C. (1998). "Modeling of magnetic properties of heat treated Dy-doped NdFeBparticles bonded in isotropic and anisotropic arrangements". IEEE Transactions on Magnetics 34 (4): 1291–1293. Bibcode:1998ITM....34.1291F. doi:10.1109/20.706525. 
  23. ^ Campbell, Peter (February 2008). "Supply and Demand, Part 2". Princeton Electro-Technology, Inc. Archived from the original on June 4, 2008. Retrieved 2008-11-09. 
  24. ^ Yu, L. Q.; Wen, Y; Yan, M (2004). "Effects of Dy and Nb on the magnetic properties and corrosion resistance of sintered NdFeB". Journal of Magnetism and Magnetic Materials 283 (2–3): 353–356. Bibcode:2004JMMM..283..353Y. doi:10.1016/j.jmmm.2004.06.006. 
  25. ^ "What is Terfenol-D?". ETREMA Products, Inc. 2003. Retrieved 2008-11-06. 
  26. ^ Kellogg, Rick; Flatau, Alison (May 2004). "Wide Band Tunable Mechanical Resonator Employing the ΔE Effect of Terfenol-D". Journal of Intelligent Material Systems & Structures (Sage Publications, Ltd) 15 (5): 355–368. doi:10.1177/1045389X04040649. 
  27. ^ Leavitt, Wendy (February 2000). "Take Terfenol-D and call me". Fleet Owner (RODI Power Systems Inc) 95 (2): 97. Retrieved 2008-11-06. 
  28. ^ "Supercritical Water Oxidation/Synthesis". Pacific Northwest National Laboratory. Archived from the original on 2008-04-20. Retrieved 2009-06-06. 
  29. ^ "Rare Earth Oxide Fluoride: Ceramic Nano-particles via a Hydrothermal Method". Pacific Northwest National Laboratory. Retrieved 2009-06-06. 
  30. ^ M.M. Hoffman, J.S. Young, J.L. Fulton (2000). "Unusual dysprosium ceramic nano-fiber growth in a supercritical aqueous solution". J Mat. Sci. 35 (16): 4177. Bibcode:2000JMatS..35.4177H. doi:10.1023/A:1004875413406. 
  31. ^ Theodore Gray (2009). The Elements. Black Dog and Leventhal Publishers. pp. 152–153. ISBN 978-1-57912-814-2. 
  32. ^ Steve Milward, Stephen Harrison, Robin Stafford Allen, Ian Hepburn, and Christine Brockley-Blatt (2004). "Design, Manufacture and Test of an Adiabatic Demagnetization Refrigerator Magnet for use in Space" http://www.ucl.ac.uk/mssl/cryogenics/documents/5LH01.pdf
  33. ^ Ian Hepburn (). "Adiabatic Demagnetization Refrigerator: A Practical Point of View" 30. http://www.ucl.ac.uk/mssl/cryogenics/documents/ADR_presentation__Compatibility_Mode_.pdf
  34. ^ Dierks, Steve (January 2003). "Dysprosium". Material Safety Data Sheets. Electronic Space Products International. Retrieved 2008-10-20. 
  35. ^ Dierks, Steve (January 1995). "Dysprosium Chloride". Material Safety Data Sheets. Electronic Space Products International. Retrieved 2008-11-07. 
  36. ^ Dierks, Steve (December 1995). "Dysprosium Fluoride". Material Safety Data Sheets. Electronic Space Products International. Retrieved 2008-11-07. 
  37. ^ Dierks, Steve (November 1988). "Dysprosium Oxide". Material Safety Data Sheets. Electronic Space Products International. Retrieved 2008-11-07. 

External links[edit]

http://en.wikipedia.org/wiki/Lycopene#External_links