Gadolinium is primarily found in the major rare earth ore minerals bastnäsite, monazite, and especially xenotime.

Ion-adsorption clay deposits in southern China are particularly rich in gadolinium.

After a complex separation of other gadolinium-containing elements, the oxide is converted with hydrofluoric acid into gadolinium fluoride. This is then reduced to metallic gadolinium using calcium, producing calcium fluoride as a byproduct. Remaining calcium residues and impurities are removed by an additional vacuum remelting process.

Due to its extremely strong paramagnetism, the most important application of gadolinium is as an MRI contrast agent in modern medical diagnostics.

Other properties of gadolinium make it highly relevant for niche applications.

Because of its high neutron absorption cross-section, gadolinium is used in control rods in nuclear reactors.

Gadolinium is also used in the production of phosphors for plasma displays and X-ray screens, as it activates green phosphorescence.

The silvery-white to grayish-white rare earth metal is ductile and malleable. Above 1508 K, its closest-packed crystal structure transforms into a body-centered cubic structure. In dry air, gadolinium is relatively stable, but in moist air it forms a non-protective, loosely adherent oxide layer that flakes off. It reacts slowly with water and dissolves in dilute acids.

Gadolinium has the highest thermal neutron capture cross-section of all known stable elements at 49,000 barns, due to its isotope Gd-157, which has a cross-section of 254,000 barns (only the unstable Xe-135 surpasses Gd-157 by about a factor of 10). However, its high burn-out rate limits its use as a control rod material in nuclear reactors.

Gadolinium is not superconducting, but ceramic high-temperature superconductors of the type Ba₂GdCu₃O₇₋ₓ with a critical temperature between 80 and 85 K are known.

Europium is a rare element on Earth, with an average abundance of about 2 ppm in the continental crust.

It occurs as a minor constituent in various lanthanide-bearing minerals. Europium is found in monazite, bastnäsite, and xenotime.

After breaking down the raw materials, such as monazite or bastnäsite, using sulfuric acid or sodium hydroxide, various separation methods can be applied.

In addition to ion exchange, a process based on liquid–liquid extraction and the reduction of Eu³⁺ to Eu²⁺ is commonly used. When bastnäsite is the starting material, cerium is first removed as cerium(IV) oxide, and the remaining rare earth elements are dissolved in hydrochloric acid. A mixture of DEHPA (di(2-ethylhexyl)phosphoric acid) and kerosene is then used in liquid–liquid extraction to separate europium, gadolinium, and samarium from the other rare earth elements. These three are further separated by selectively reducing europium to Eu²⁺ and precipitating it as poorly soluble europium(II) sulfate, while the other ions remain in solution.

Metallic europium can be produced by reacting europium(III) oxide with lanthanum or mischmetal. When this reaction is carried out under vacuum, europium distills off and can thus be separated from other metals and impurities.

The first major technical application of europium was the production of europium-doped yttrium vanadate. This red phosphor, discovered in 1964 by Albert K. Levine and Frank C. Palilla, soon played a key role in the development of color television. As a result, the first rare earth mine, operating since 1954 in Mountain Pass, California, was significantly expanded to meet demand.

Europium continues to be used as a dopant in the production of phosphors for aircraft instrument displays and compact fluorescent lamps (CFLs). Phosphors containing both divalent and trivalent europium are used for different colors.

For red phosphors, europium-doped yttrium oxide (Y₂O₃:Eu³⁺) is primarily used. Previously, yttrium oxysulfide and the first significant red phosphor, yttrium vanadate:Eu³⁺, were also used. Eu²⁺ is typically used as a blue phosphor in compounds like strontium chlorophosphate (Sr₅(PO₄)₃Cl:Eu²⁺, also known as strontium chloroapatite, SCAP) and barium magnesium aluminate (BaMgAl₁₁O₁₇:Eu²⁺, BAM).

Plasma displays require phosphors that convert VUV radiation emitted by the noble gas plasma into visible light. Europium-doped phosphors are used here for both the blue and red parts of the spectrum — BAM for blue, and (Y,Gd)BO₃:Eu³⁺ for red.

Due to its ability to absorb neutrons, europium can also be used in control rods for nuclear reactors. Europium-containing control rods have been tested in various Soviet experimental reactors such as BOR-60 and BN-600.

As europium hexaboride, it is also used as a coating for oxide cathodes in thermionic emission applications.

Europium fluorescence is used as an anti-counterfeiting feature in euro banknotes.

This fluorescence property is also useful in fluorescence spectroscopy. Europium can be bound in specific complexes that selectively react and accumulate at desired locations, such as with certain proteins.

Soluble europium compounds are mildly toxic.

As a base metal, europium is one of the most reactive rare earth elements. When exposed to air, the silvery, shiny metal tarnishes immediately. At temperatures above 150 °C, it ignites and burns with a red flame to form the sesquioxide Eu₂O₃. In water, it reacts with the evolution of hydrogen to form the hydroxide.

Europium reacts with the halogens fluorine, chlorine, bromine, and iodine to form the respective trihalides. When reacting with hydrogen, non-stoichiometric hydride phases are formed, with hydrogen occupying the interstitial spaces of the metal’s crystal lattice.

Europium dissolves slowly in water but rapidly in acids, producing hydrogen gas and the colorless Eu³⁺ ion. The also colorless Eu²⁺ ion can be obtained via electrolytic reduction at the cathode in aqueous solution. It is the only divalent lanthanoid ion that is stable in aqueous solution. Europium also dissolves in liquid ammonia, forming a deep blue solution similar to alkali metals, in which solvated electrons are present.

The Eu³⁺ cation, like Sm³⁺, Tb³⁺, and Dy³⁺, can emit visible light when coordinated in a suitable complex and excited at specific wavelengths. While Eu³⁺ is colorless in aqueous solution, coordination with organic ligands possessing extended π-electron systems greatly enhances its luminescent properties via the antenna effect. The π-electrons of the ligand absorb incoming light (approx. 355 nm) and transfer the energy to the 5d electrons of Eu³⁺, which are then excited to the 4f orbitals. When these electrons return to their ground state, visible light (approx. 610 nm) is emitted.

With a density of 5.245 g/cm³, europium has an unusually low density — significantly lower than that of neighboring lanthanoids such as samarium or gadolinium, and even lower than lanthanum.

This also applies to its comparatively low melting point (826 °C) and boiling point (1440 °C), in contrast to the typical trend among the lanthanoids (e.g., gadolinium melts at 1312 °C and boils at 3000 °C). These anomalies contradict the lanthanoid contraction and are attributed to europium’s electron configuration. Because its 4f shell is half-filled, only two valence electrons are available for metallic bonding, resulting in weaker bonding forces and a significantly larger atomic radius — a phenomenon also observed in ytterbium.

Under normal conditions, europium crystallizes in a body-centered cubic (bcc) structure with a lattice parameter of a = 455 pm. Two additional high-pressure phases are known. Unlike other lanthanoids, europium (similar to ytterbium) does not exhibit a double-hexagonal or samarium-type structure. The first phase transition occurs at 12.5 GPa, above which europium crystallizes in a hexagonal close-packed (hcp) structure with lattice parameters a = 241 pm and c = 545 pm. At pressures above 18 GPa, a third phase (Eu-III), similar to the hcp arrangement, has been identified.

Europium ions embedded in suitable host lattices show pronounced fluorescence. The emitted wavelength depends on the oxidation state. Eu³⁺ fluoresces intensely red, largely independent of the host lattice, emitting between 613 and 618 nm. In contrast, Eu²⁺ fluorescence is more sensitive to the host material. For example, emission occurs at 447 nm (blue) in barium magnesium aluminate (BaMgAl₁₁O₁₇:Eu²⁺), and at 520 nm (green) in strontium aluminate (SrAl₂O₄:Eu²⁺).

While ¹⁵³Eu is stable, evidence suggests that ¹⁵¹Eu is an alpha emitter. The lower limit of its half-life is estimated at 1.7 trillion years. Europium and its compounds are considered toxic. Metal dusts are both flammable and explosive hazards.

As a heavy rare earth element (HREE), erbium is more commonly found in HREE-enriched minerals such as xenotime and euxenite. Additionally, erbium occurs in ion-adsorption clays (clay deposits), which, due to their relatively simple processing despite the low percentage of rare earth elements, represent the most important source of HREEs. The primary sources are ion-adsorption clay minerals from southern China (Jiangxi and Guangdong provinces) and Myanmar.

After an elaborate separation of other erbium-associated elements, the oxide is converted with hydrofluoric acid into erbium fluoride. It is then reduced to metallic erbium using calcium, producing calcium fluoride as a byproduct. Remaining calcium residues and impurities are removed through an additional vacuum remelting process.

Its unique interaction with light accounts for most of the element’s applications. Unlike cerium or lanthanum, its uses are more specialized but absolutely crucial for modern technologies.

In fiber optic networks, erbium-doped glasses serve as optical amplifiers. These erbium-doped fiber amplifiers (EDFAs) form the backbone of the global internet. They enable data transmission over thousands of kilometers under the oceans without the need for electrical signal regeneration along the way.

In medicine, erbium lasers (Er:YAG lasers — erbium-doped yttrium aluminum garnet) are used in dermatology and dentistry due to their precise and controlled effects.

Besides medical lasers, erbium is also used in other high-precision lasers: erbium-doped crystals (such as Er:YAG, Er:YSGG) are employed in lasers for precise cutting, welding, and marking in industrial applications.

Erbium oxide, which has a beautiful and distinctive pink to rose color, is used as a dye for glass, jewelry, and sunglasses.

(Er₂O₃) exhibits a very attractive and characteristic pink to rose hue.

Besides its optical properties, erbium is useful in nuclear power due to its ability to easily absorb free neutrons. This makes it suitable for use in control rods in nuclear reactors.

Furthermore, erbium alloys are used in cryocoolers for applications at liquid helium temperatures because of their high specific heat capacity.

The occurrence of dysprosium in the continental Earth’s crust is about 5.2 ppm. In terms of abundance, it ranks behind most of the light rare earth elements such as cerium, neodymium, and samarium, but ahead of most heavy rare earths like erbium, ytterbium, and holmium.

Minerals with particularly high dysprosium content include xenotime and gadolinite-(Y). In contrast, ores important for extracting other lanthanides, such as monazite and bastnäsite, contain only small amounts of dysprosium.

The main sources of dysprosium are ion-adsorption clay minerals (clay deposits) found in southern China (Jiangxi and Guangdong provinces) and Myanmar.

In these clay deposits, the rare earth elements are not part of a crystal structure but are adsorbed as ions onto clay particles. This allows for their extraction via ion-exchange processes, which are especially simple and cost-effective. Crucially, these deposits are highly enriched with valuable heavy rare earth elements like dysprosium and terbium.

After an elaborate separation of other dysprosium-associated elements, the oxide is converted with hydrofluoric acid to dysprosium fluoride. It is then reduced with calcium to metallic dysprosium, producing calcium fluoride as a byproduct. Remaining calcium residues and impurities are removed through an additional vacuum remelting process. High-purity dysprosium is obtained after vacuum distillation.

Commercial separation is performed by liquid-liquid extraction or ion-exchange methods. The metal is produced by metallothermic reduction of the anhydrous halides using alkali or alkaline earth metals. Further purification of the metal is achieved by vacuum distillation.

Dysprosium exists in three allotropes (structural forms). The α-phase is hexagonally close-packed (HCP) with lattice parameters a = 3.5915 Å and c = 5.6501 Å at room temperature. Upon cooling to approximately 90 K (-183 °C / -297 °F), the ferromagnetic order is accompanied by an orthorhombic distortion of the HCP lattice. The β-phase has lattice parameters a = 3.595 Å, b = 6.184 Å, and c = 5.678 Å at 86 K (-187 °C / -305 °F). The γ-phase is body-centered cubic (BCC) with a = 4.03 Å at 1381 °C (2518 °F).

The main applications of dysprosium are as alloying additions to Nd₂Fe₁₄B permanent magnet materials (where part of the neodymium is replaced by dysprosium) to increase both the Curie temperature and especially the coercive field strength, thereby improving the high-temperature performance of the alloy. The metal is also a component of the magnetostrictive material Terfenol D (Tb₀.₃Dy₀.₇Fe₂).

Due to its relatively high neutron absorption cross-section, dysprosium is used in control rods for nuclear reactors. Its compounds have been employed in the production of laser materials and phosphor activators, as well as in halogen metal vapor lamps.

The economic and technical significance of dysprosium is relatively low. Its annual production is estimated at less than 100 tons. It is used in various alloys, specialty magnets, and, alloyed with lead, as shielding material in nuclear reactors. However, its use in magnets for wind turbines has contributed to making rare earth metals a scarce resource. Additionally, the world’s largest supplier, China, restricts exports to increase domestic value creation.