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