Rare Earth Materials

Definition, classification and current supply list for high-purity oxides and metals.

What are rare earths?

Rare-earth elements (REEs), also called rare-earth metals, are a set of 17 chemically similar metallic elements: the fifteen lanthanides (lanthanum, La, atomic number 57, through lutetium, Lu, atomic number 71) together with scandium (Sc, 21) and yttrium (Y, 39). Scandium and yttrium are included because they occur in the same ore minerals as the lanthanides and follow them through chemical separation, even though they sit in Group 3 of the periodic table rather than in the f-block.

The name is a historical misnomer. With the exception of radioactive promethium, rare earths are not scarce in the Earth’s crust. Cerium is comparable in crustal abundance to copper; yttrium, lanthanum and neodymium are in the same broad range as nickel, zinc or lead. What is rare is a concentrated, easily mined deposit of a single element. In nature the rare earths occur together in minerals such as bastnäsite, monazite, xenotime and ion-adsorption clays. Separating them into individual high-purity oxides and metals is the expensive step.

A common working split is light rare earths (lanthanum to europium) and heavy rare earths (gadolinium to lutetium). Yttrium is treated as a heavy rare earth in ore accounting because it reports with that group. Gadolinium, dysprosium and yttrium — the rare earths on the Ametheus list — sit in this heavier, higher-value part of the series. They are used where ordinary metals cannot deliver the required magnetic, optical, nuclear or ceramic behaviour.

Why these elements are specified

Industry does not buy “rare earths” as a generic commodity. It buys a named oxide or metal at a stated purity because a few tens of parts per million of the wrong neighbour element can change phosphor colour, magnet coercivity, neutron absorption or ceramic sinter density. The grades below are minimum guaranteed purities. Each shipment should move with a certificate of analysis. For oxides, confirm whether the figure is relative to total rare-earth oxide (REO / TREO) or absolute versus all impurities.

Current Ametheus supply list

Classification note. Strontium is not a rare-earth element. It is an alkaline-earth metal in Group 2 of the periodic table. Ametheus lists it here because it can be supplied with the same industrial metals programme for foundry and specialty customers.

Product notes

Gadolinium oxide — Gd2O3

4N — 99.99% min  ·  CAS 12064-62-9  ·  Heavy rare earth oxide

White, thermally stable oxide and the usual commercial form of gadolinium. Gadolinium combines a very large thermal-neutron capture cross-section with a high magnetic moment. Those two properties drive demand in nuclear control materials and in medical imaging chemistry. The oxide is also a precursor for gadolinium metal, garnet additives and high-index optical glass.

• Neutron-absorbing and burnable-poison formulations for nuclear reactors
• Precursor stream for MRI-related gadolinium chemistry and scintillator / X-ray screen phosphors
• Additive in yttrium aluminium and yttrium iron garnets
• High-index optical glass and magneto-caloric research materials

Yttrium oxide (yttria) — Y2O3

5N — 99.999% min  ·  CAS 1314-36-9  ·  Rare earth oxide

Five-nines yttria is specified where residual neighbours would damage optical transmission, phosphor chromaticity or ceramic grain structure. Yttrium oxide is chemically durable and is the standard stabilizer that converts zirconia into yttria-stabilized zirconia (YSZ), used for thermal-barrier coatings, oxygen sensors and metal-free dental restorations.

• YSZ for thermal-barrier coatings, dental ceramics and automotive oxygen sensors
• Host lattice for LED and display phosphors, including europium-doped red systems
• Optical coatings, infrared windows and laser-host ceramics
• Precursor chemistry for YBCO high-temperature superconductors

Dysprosium oxide — Dy2O3

4N — 99.99% min  ·  CAS 1308-87-8  ·  Heavy rare earth oxide

Primary industrial use is as feedstock for dysprosium metal added to neodymium–iron–boron magnets. A small dysprosium addition raises coercivity so the magnet retains strength at the operating temperature of an EV traction motor or a wind-turbine generator. The oxide is also used in nuclear control materials, metal-halide lamp chemistry and selected magneto-optical formulations.

• NdFeB permanent magnets for electric vehicles and wind turbines
• Dysprosium metal and magnetostrictive alloys such as Terfenol-type compositions
• Neutron-absorbing control-rod materials
• Phosphors, metal-halide lamps and magneto-optical media

Yttrium metal — Y

3N — 99.9% min  ·  CAS 7440-65-5  ·  Rare earth metal

Silvery rare-earth metal used as an alloying addition and as a starting metal for compounds, master alloys and evaporation or sputtering sources. Modest additions strengthen aluminium and magnesium alloys and improve high-temperature behaviour. Handle and pack under conditions that limit oxygen pickup.

• Strengthening addition in aluminium, magnesium and chromium alloys
• Master alloys and metallurgical additives
• Feedstock for phosphors, electrodes, electronic filters and superconductor research
• Specialty electrodes and high-performance spark-plug materials

Strontium metal — Sr

2N — 99% min  ·  CAS 7440-24-6  ·  Alkaline-earth metal — not a rare earth

Soft, highly reactive silvery metal that tarnishes in air and must be stored sealed or under inert cover. In foundries, small additions of strontium modify the eutectic silicon in aluminium–silicon casting alloys, refining the microstructure and improving ductility and machinability of engine and structural castings. It is also a precursor for strontium compounds used in ferrite magnets and ceramics.

• Eutectic modifier for Al–Si casting alloys in automotive and aerospace foundries
• Precursor for strontium compounds used in ferrite magnets and ceramics
• Specialty metallurgy and laboratory inventory

Purity notation

The “N” grade counts the number of nines in the purity percentage. It is a compact way to state a minimum, not a full impurity spectrum. Buyers who care about a particular contaminant (iron, silicon, calcium, carbon, oxygen, or a neighbouring rare earth) should write that limit into the purchase specification.

Typical end markets

• Clean energy — dysprosium oxide for high-temperature NdFeB magnets in EV motors and wind generators; yttria for sensors and fuel-cell ceramics.
• Medical and imaging — gadolinium oxide as a precursor in MRI-related chemistry, scintillators and intensifying screens.
• Optics and electronics — 5N yttrium oxide for phosphors, optical coatings, laser hosts and specialty glass.
• Nuclear — gadolinium and dysprosium oxides for neutron-absorbing control and burnable-poison formulations.
• Ceramics — yttria-stabilized zirconia for dental, thermal-barrier and oxygen-ion conducting ceramics.
• Foundry metals — yttrium metal in light alloys; strontium metal as an Al–Si eutectic modifier.

Enquiry guidance

When requesting availability, state product name, grade, quantity, destination, preferred form (oxide powder size; metal as ingot, pieces or other agreed shape), packing and any process-critical impurity limits. Reactive metals — yttrium and especially strontium — require sealed or inert packaging. Ametheus will confirm lot availability against a certificate of analysis. Do not publish or resell a tighter grade than the certificate that travels with the goods.

Ametheus  ·  Rare earth oxides, rare earth metals and selected specialty metals.

This brief is written for industrial and laboratory buyers. Typical application notes are informative only; certified analysis and the purchase specification govern each shipment.

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