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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 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 (χv ≈ 5.44×10−3) 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.

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.[11] Dysprosium has a simple ferromagnetic ordering at temperatures below its Curie temperature of 90.5 K (−182.7 °C), at which point it undergoes a first-order phase transition from the orthorhombic crystal structure to hexagonal close-packed (hcp).[3] 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 (−94 °C).[12] It transforms from the hcp phase to the body-centered cubic phase at 1,654 K (1,381 °C).

Chemical properties
Dysprosium metal retains its luster in dry air but it will tarnish slowly in moist air, and 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:[citation needed]

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 SO2−
4 (aq) + 3 H2 (g)
The resulting compound, dysprosium(III) sulfate, is noticeably paramagnetic.

Compounds

Dysprosium sulfate, Dy2(SO4)3
See also: Dysprosium 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.[16] 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
Main article: Isotopes of dysprosium
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%.