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= Dysprosium =
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Introduction
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Dysprosium is a chemical element; it has symbol Dy and atomic number
66. It is a rare-earth element in the lanthanide series with a
metallic silver luster. Dysprosium is never found in nature as a free
element, though, like other lanthanides, it is found in various
minerals, such as xenotime. Naturally occurring dysprosium is composed
of seven isotopes, the most abundant of which is 164Dy.
Dysprosium was first identified in 1886 by Paul Émile Lecoq de
Boisbaudran, but it was not isolated in pure form until the
development of ion-exchange techniques in the 1950s. Dysprosium is
used to produce neodymium-iron-boron (NdFeB) magnets, which are
crucial for electric vehicle motors and the efficient operation of
wind turbines. It 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 (a magnetostrictive material). Soluble
dysprosium salts are mildly toxic, while the insoluble salts are
considered non-toxic.
Physical properties
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Dysprosium sample
Dysprosium is a rare-earth element and has a metallic, bright silver
luster. It is quite soft and can be machined without sparking if
overheating is avoided. Dysprosium's physical characteristics can be
greatly affected by even small amounts of impurities.
Dysprosium and holmium have the highest magnetic strengths of the
elements, especially at low temperatures. Dysprosium has a simple
ferromagnetic ordering at temperatures below its Curie temperature of
90.5 K, at which point it undergoes a first-order phase transition
from the orthorhombic crystal structure to hexagonal close-packed
(hcp). It then has a helical antiferromagnetic state, in which all of
the atomic magnetic 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. It transforms from the hcp phase to the
body-centered cubic phase at 1654 K.
Chemical properties
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Dysprosium metal retains its luster in dry air, but it will tarnish
slowly in moist air. It burns readily to form dysprosium(III) oxide:
:4 Dy + 3 O2 → 2 Dy2O3
Dysprosium is quite electropositive and reacts slowly with cold water
(and quickly with hot water) to form dysprosium hydroxide:
:2 Dy (s) + 6 H2O (l) → 2 Dy(OH)3 (aq) + 3 H2 (g)
Dysprosium hydroxide decomposes to form DyO(OH) at elevated
temperatures, which then decomposes again to dysprosium(III) oxide.
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 (l) → 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+
complex:
:2 Dy (s) + 3 H2SO4 (aq) → 2 Dy3+ (aq) + 3 (aq) + 3 H2 (g)
The resulting compound, dysprosium(III) sulfate, is noticeably
paramagnetic.
Compounds
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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.
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.
Dysprosium carbonate, Dy2(CO3)3, and dysprosium sulfate, Dy2(SO4)3,
result from similar reactions. 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. Two of the most abundant dysprosium carbonates,
Dy2(CO3)3·2-3H2O (similar to the mineral tengerite-(Y)), and DyCO3(OH)
(similar to minerals kozoite-(La) and kozoite-(Nd)), are known to form
via a poorly ordered (amorphous) precursor phase with a formula of
Dy2(CO3)3·4H2O. This amorphous precursor consists of highly hydrated
spherical nanoparticles of 10-20 nm diameter that are exceptionally
stable under dry treatment at ambient and high temperatures.
Dysprosium forms several intermetallics, including the dysprosium
stannides.
Isotopes
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Naturally occurring dysprosium is composed of seven isotopes: 156Dy,
158Dy, 160Dy, 161Dy, 162Dy, 163Dy, and 164Dy. These are all considered
stable, although only the last two are theoretically stable: the
others can theoretically undergo alpha decay. 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%. Dysprosium is the
heaviest element to have isotopes that are predicted to be stable
rather than observationally stable isotopes that are predicted to be
radioactive.
Twenty-nine radioisotopes have been synthesized, ranging in atomic
mass from 138 to 173. The most stable of these is 154Dy, with a
half-life of approximately 3 years, followed by 159Dy with a half-life
of 144.4 days. The least stable is 138Dy, with a half-life of 200 ms.
As a general rule, 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. However, 154Dy decays primarily by alpha decay,
and 152Dy and 159Dy decay primarily by electron capture. 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.
History
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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. 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. On succeeding, he named the
element 'dysprosium' from the Greek 'dysprositos' (δυσπρόσιτος),
meaning "hard to get". 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.
Due to its role in permanent magnets used for wind turbines, it has
been argued that dysprosium will be one of the main objects of
geopolitical competition in a world running on renewable energy. But
this perspective has been criticised for failing to recognise that
most wind turbines do not use permanent magnets and for
underestimating the power of economic incentives for expanded
production.
In 2011, a Bose-Einstein condensate of Dy atoms was obtained for the
first time.
In 2021, Dy was turned into a 2-dimensional supersolid quantum gas.
Occurrence
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Xenotime
While dysprosium is never encountered as a free element, it 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. No
dysprosium-dominant mineral (that is, with dysprosium prevailing over
other rare earths in the composition) has yet been found.
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). The concentration
of Dy in the Earth's crust is about 5.2 mg/kg and in sea water 0.9
ng/L.
Production
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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:
: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.
About 3100 tonnes of dysprosium were produced worldwide in 2021, with
40% of that total produced in China, 31% in Myanmar, and 20% in
Australia. Dysprosium prices have climbed over time, from $7 per pound
in 2003, to $130 a pound in late 2010, to $1,400/kg in 2011 and then
falling to $240/kg in 2015, largely due to illegal production in China
which circumvented government restrictions. As of April 2025, the
price is around USD$203/kg.
Currently, most dysprosium is being obtained from the ion-adsorption
clay ores of southern China. the Browns Range Project pilot plant,
160 km south east of Halls Creek, Western Australia, is producing 50 t
per annum.
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 predicted a shortfall of dysprosium
before 2015. As of late 2015, there is a nascent rare earth (including
dysprosium) extraction industry in Australia.
Applications
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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. Dysprosium-cadmium chalcogenides are sources
of infrared radiation, which is useful for studying chemical
reactions. Because dysprosium and its compounds are highly susceptible
to magnetization, they are employed in various data-storage
applications, such as in hard disks. Dysprosium is increasingly in
demand for the permanent magnets used in electric-car motors and
wind-turbine generators.
Neodymium-iron-boron magnets can have up to 6% of the neodymium
substituted by dysprosium to raise the coercivity for demanding
applications, such as drive motors for electric vehicles and
generators for wind turbines. This substitution would require up to
100 grams of dysprosium per electric car produced. Based on Toyota's
projected 2 million units per year, the use of dysprosium in
applications such as this would quickly exhaust its available supply.
The dysprosium substitution may also be useful in other applications
because it improves the corrosion resistance of the magnets.
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, which is employed in transducers, wide-band
mechanical resonators, and high-precision liquid-fuel injectors.
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.
Nanofibers of dysprosium compounds have high strength and a large
surface area. Therefore, they can be used to reinforce other materials
and act 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 bars for 17 hours. This material is remarkably robust, surviving
over 100 hours in various aqueous solutions at temperatures exceeding
400 °C without redissolving or aggregating. Additionally, dysprosium
has been used to create a two-dimensional supersolid in a laboratory
environment. Supersolids are expected to exhibit unusual properties,
including superfluidity.
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.
Several paramagnetic crystal salts of dysprosium (dysprosium gallium
garnet, DGG; dysprosium aluminium garnet, DAG; dysprosium iron garnet,
DyIG) are used in adiabatic demagnetization refrigerators.
The trivalent dysprosium ion (Dy3+) has been studied due to its
downshifting luminescence properties. Dy-doped yttrium aluminium
garnet (Dy:YAG) excited in the ultraviolet region of the
electromagnetic spectrum results in the emission of photons of longer
wavelength in the visible region. This idea is the basis for a new
generation of UV-pumped white light-emitting diodes.
The stable isotopes of dysprosium have been laser cooled and confined
in magneto-optical traps for quantum physics experiments. The first
Bose and Fermi quantum degenerate gases of an open shell lanthanide
were created with dysprosium. Because dysprosium is highly
magnetic--indeed it is the most magnetic fermionic element and nearly
tied with terbium for most magnetic bosonic atom--such gases serve as
the basis for quantum simulation with strongly dipolar atoms.
Due to its strong magnetic properties, dysprosium alloys are used in
the marine industry's sound navigation and ranging (SONAR) system. The
inclusion of dysprosium alloys in the design of SONAR transducers and
receivers can improve sensitivity and accuracy by providing more
stable and efficient magnetic fields.
Precautions
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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 extinguished with water. It
can react with water to produce flammable hydrogen gas. Dysprosium
chloride fires can be extinguished with water. Dysprosium fluoride and
dysprosium oxide are non-flammable. Dysprosium nitrate, Dy(NO3)3, is a
strong oxidizing agent and readily ignites on contact with organic
substances.
Soluble dysprosium salts, such as dysprosium chloride and dysprosium
nitrate are mildly toxic when ingested. 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 (cf. lethal dose of 300 grams
of common table salt for a 100 kilogram human). The insoluble salts
are non-toxic.
External links
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* [
https://education.jlab.org/itselemental/ele066.html It's Elemental
- Dysprosium]
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Original Article:
http://en.wikipedia.org/wiki/Dysprosium
