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 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
has relatively few applications where it cannot
be replaced by other chemical elements. 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.
== Characteristics ==
=== 
Physical properties ===
Dysprosium is a rare earth element that 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 85 K (−188.2 °C).
Above 85 K (−188.2 °C), it turns into a
helical antiferromagnetic state in which all
of the atomic moments in a particular basal
plane layer are parallel, and oriented at
a fixed angle to the moments of adjacent layers.
This unusual antiferromagnetism transforms
into a disordered (paramagnetic) state at
179 K (−94 °C).
=== Chemical properties ===
Dysprosium metal tarnishes slowly in air and
burns readily to form dysprosium(III) oxide:
4 Dy + 3 O2 → 2 Dy2O3Dysprosium 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+ complex:
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 ===
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, tengerite-(Dy) (Dy2(CO3)3·2–3H2O)
and kozoite-(Dy) (DyCO3(OH)) 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.
=== Isotopes ===
Naturally occurring dysprosium is composed
of seven 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%.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. 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 ==
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.
== Occurrence ==
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 ==
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 LiClThe 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
100 tonnes of dysprosium are produced worldwide
each year, with 99% of that total produced
in China. Dysprosium prices have climbed nearly
twentyfold, from $7 per pound in 2003, to
$130 a pound in late 2010. The price increased
to $1,400/kg in 2011 but fell to $240 in 2015,
largely due to illegal production in China
which circumvented government restrictions.Currently,
most dysprosium is being obtained from the
ion-adsorption clay ores of southern China.
As of November 2018 the Browns Range Project
pilot plant, 160 km south east of Halls Creek,
Western Australia is producing 50 tonnes (49
long tons) 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 predict a shortfall of dysprosium
before 2015. As of late 2015, there is a nascent
rare earth (including dysprosium) extraction
industry in Australia.
== Applications ==
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.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 Aluminum Garnet, DAG; Dysprosium
Iron Garnet, DyIG) are used in adiabatic demagnetization
refrigerators.The trivalent dysprosium ion
(Dy3+) has been studied due its downshifting
luminescence properties. Dy-doped yttrium
aluminium garnet (YAG:Dy) 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.
== Precautions ==
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. Dysprosium
chloride fires, however, can be extinguished
with water, while dysprosium fluoride and
dysprosium oxide are non-flammable. Dysprosium
nitrate, Dy(NO3)3, is a strong oxidizing agent
and will readily ignite 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. The insoluble
salts, however, are non-toxic
