Rare earth metals

rare-earth-metals

16 materials across 1 types

About rare earth metals

Rare earth metals (neodymium, dysprosium, gadolinium, cerium, lanthanum, yttrium, scandium and more): density, melting point and supply data with sources.

The rare earths are a group of seventeen similar metals. They are used in magnets, lasers, phosphors, catalysts and alloys, and they are mined and refined mostly in a few countries, which makes supply a design risk.

Most are reactive and oxidise in air, so purity and handling are stated with the values.

At a glance

Highest density: Lutetium reaches 9.84 g/cm³. Lowest: Scandium starts at 2.98 g/cm³. (16 of 16 grades have a sourced value.)
Highest melting point: Lutetium reaches 1,663 °C. Lowest: Cerium starts at 798 °C. (16 of 16 grades have a sourced value.)
Highest electrical resistivity: Gadolinium (Gd) reaches 0.0000013 Ω·m. Lowest: Ytterbium (Yb) starts at 2.5e-7 Ω·m. (10 of 16 grades have a sourced value.)

Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.

How they compare

The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.

Rare earth metals: how the grades compare
Material	Density	Melting point	Electrical resistivity	Thermal conductivity	Young's modulus	Thermal expansion
Neodymium (Nd)magnet alloy feedstock and solid-state laser dopant	6.8 to 7.01 g/cm³	1,021 to 1,022 °C	6.4e-7 Ω·m	16.5 to 17 W/(m·K)	41 to 41.4 GPa	6.7 to 9.6 ppm/K
Dysprosiumpermanent-magnet alloying element and neutron absorber	8.54 to 8.55 g/cm³	1,409 to 1,412 °C	no data	11 W/(m·K)	61 GPa	9.9 ppm/K
Gadolinium (Gd)neutron absorber, magnetocaloric material and scintillator host	7.89 to 7.9 g/cm³	1,312 to 1,313 °C	0.0000013 Ω·m	10.6 W/(m·K)	54.8 to 56.2 GPa	6.4 to 11.1 ppm/K
Ceriumrare-earth metal for alloys and lighter flints; cerium oxide (ceria) used as a glass dopant	6.75 to 6.77 g/cm³	798 to 799 °C	8.5e-7 Ω·m	11.3 W/(m·K)	no data	8 ppm/K
Lanthanumoptical-glass and battery-alloy rare-earth metal; LaB6 thermionic emitter in electric-propulsion cathodes	6.14 to 6.17 g/cm³	918 to 921 °C	615 nΩ·m	13 to 13.4 W/(m·K)	36.6 to 37 GPa	5.1 ppm/K
Praseodymiummagnet and optical rare-earth metal	6.71 to 6.77 g/cm³	931 °C	7.0e-7 Ω·m	12.5 W/(m·K)	37.3 GPa	4.5 ppm/K
Samarium (Sm)neutron absorber and samarium-cobalt magnet metal	7.35 to 7.52 g/cm³	1,072 °C	9.4e-7 Ω·m	13 W/(m·K)	50 GPa	12.7 ppm/K
Europiumred phosphor activator, neutron absorber and scintillator activator	5.25 to 5.26 g/cm³	822 to 826 °C	9.0e-7 Ω·m	13.9 to 14 W/(m·K)	18 to 18.2 GPa	35 ppm/K
Terbium (Tb)green phosphor activator, magnetostrictive alloy component (Terfenol-D) and Faraday rotator garnet	8.23 g/cm³	1,356 °C	0.0000011 Ω·m	11 to 11.1 W/(m·K)	55.7 to 56 GPa	10.3 ppm/K
Holmiummagnetic pole-piece material and neutron absorber	8.79 g/cm³	1,461 to 1,474 °C	814 nΩ·m	16 to 16.2 W/(m·K)	64.8 to 65 GPa	11.2 ppm/K
Erbiumoptical fibre amplifier dopant and near-infrared laser ion	9.01 to 9.06 g/cm³	1,529 °C	8.6e-7 Ω·m	14.5 W/(m·K)	69.9 GPa	no data
Thulium (Tm)2 µm laser gain medium and dopant, and the Tm-170 portable X-ray source	9.32 g/cm³	1,545 °C	142 to 676 nΩ·m	16.9 to 17 W/(m·K)	56 to 74 GPa	13.3 ppm/K
Ytterbium (Yb)dopant for fibre lasers, stainless-steel additive and reactive rare-earth metal	6.54 to 6.98 g/cm³	819 to 824 °C	2.5e-7 to 2.8e-7 Ω·m	34.9 to 38.5 W/(m·K)	17.8 to 24 GPa	26.3 ppm/K
Lutetiumscintillator component (LYSO, LuAG) and catalyst metal	9.84 g/cm³	1,663 °C	6.8e-7 Ω·m	16.4 W/(m·K)	84 GPa	12.5 ppm/K
Yttriumphosphor and laser-crystal element, and an alloy addition for magnesium and other metals	4.47 g/cm³	1,522 to 1,526 °C	596 nΩ·m	17.2 W/(m·K)	63.5 GPa	11.2 ppm/K
Scandiumaluminium alloying element for aerospace parts, with smaller uses in solid oxide fuel cells and metal-halide lamps	2.98 to 2.99 g/cm³	1,540 to 1,541 °C	562 nΩ·m	15.8 to 16 W/(m·K)	74 to 74.4 GPa	9.97 to 10.2 ppm/K

What these materials are made of

Composition by weight, as printed in the sources for each grade (the first constituents listed).

Composition of each grade
Material	Main constituents
Neodymium (Nd)	Nd 100.0%
Dysprosium	Dy 100.0%
Gadolinium (Gd)	Gd 100.0%
Cerium	Ce 100.0%
Lanthanum	La 100.0%
Praseodymium	Pr 100.0%
Samarium (Sm)	Sm 100.0%
Europium	Eu 100.0%
Terbium (Tb)	Tb 100.0%
Holmium	Ho 100.0%
Erbium	Er 100.0%
Thulium (Tm)	Tm 100.0%
Ytterbium (Yb)	Yb 100.0%
Lutetium	Lu 100.0%
Yttrium	Y 100.0%
Scandium	Sc 100.0%

Where they are used

Uses
Use	Grades
Nd:YAG laser altimeter transmitter on Mars Global Surveyor (MOLA, launched 5 November 1996)	Neodymium (Nd)
Neodymium-glass laser amplifiers at the National Ignition Facility	Neodymium (Nd)
Nd-Fe-B permanent magnets for electric motors and generators, with neodymium as the magnet element	Neodymium (Nd)
Nuclear reactor control rods (potential use)	Dysprosium
Neodymium-iron-boron permanent magnets for motors and generators	Dysprosium
Neutron absorber in some nuclear reactors and neutron radiography shielding	Gadolinium (Gd)
Gamma-ray detector on the GRID CubeSat (GAGG:Ce scintillator, a gadolinium garnet)	Gadolinium (Gd)
Magnetic refrigerator using the magnetocaloric effect (research)	Gadolinium (Gd)
Solar-cell cover glass made from 1.5% ceria-doped Micro-Sheet (cerium oxide dopant)	Cerium
Metal alloys containing cerium, including mischmetal	Cerium
Lanthanum oxide in high-index optical glass for camera and telescope lenses (ground-manufactured)	Lanthanum
Lanthanum hexaboride (LaB6) thermionic emitter in a hollow cathode for Hall thrusters (a compound, not the metal; design record, no flight reported)	Lanthanum
Lanthanum-containing alloy anode in nickel-metal hydride (NiMH) rechargeable batteries (an alloy, not the metal)	Lanthanum
Neodymium-praseodymium permanent magnets for motors, headphones and loudspeakers	Praseodymium
Pr3+ doped lasers and fibre amplifiers	Praseodymium
Magnesium alloys with praseodymium for aircraft engine parts	Praseodymium

When each grade fits

Best use and weak spots of each grade
Material	Best for	Weakest at
Neodymium (Nd)	Magnet-grade and laser-grade neodymium, where a 1064 nm Nd:YAG laser or a Nd-Fe-B magnet is the goal (Wikipedia, NASA MOLA paper)	Tarnishes in air, reacts with water and releases hydrogen with acids, and fine chips and powder are flammable (Wikipedia, Lesker MSDS)
Dysprosium	Neutron absorption in nuclear control rods (PubChem lists this as a potential use) and rare-earth magnet alloys (USGS)	Oxidises in moist air and reacts with water and dilute acids to release hydrogen; powder and thin foil are flammable solids (ESPI, PubChem)
Gadolinium (Gd)	Neutron absorption (259,000 barns for Gd-157) and room-temperature magnetocaloric research near its 293.4 K Curie transition (Wikipedia)	Fine chips and dust that ignite, and metal that releases hydrogen on contact with water (Apollo SDS, Lesker MSDS)
Cerium	Ceria (cerium oxide) as a UV-blocking, radiation-resistant dopant in solar-cell cover glass (NASA 1973 laboratory test)	Handling: finely divided metal is pyrophoric, and the metal reacts with water and moist air (Ames SDS, CAMEO)
Lanthanum	Optical glass and camera-lens additive (lanthanum oxide, high refractive index), and LaB6 emitters in Hall-thruster cathodes (Wikipedia; NASA Tech Briefs 2010)	Handling: a flammable solid that tarnishes in air within hours and releases hydrogen with water and acids (ESPI, Lesker, Wikipedia)
Praseodymium	High-power NdPr permanent magnets, and Pr3+ optical dopants in lasers and fibre amplifiers (Wikipedia; USGS)	Handling: the metal tarnishes in air, reacts with water, and fine powder is classed as pyrophoric (H250) in two supplier sheets (Wikipedia; Apollo Scientific; Stanford Advanced Materials)
Samarium (Sm)	Neutron capture in reactor control (Sm-149 thermal capture cross section 40,140 barns), and as the rare-earth part of high-temperature samarium-cobalt magnets	Reactive metal: tarnishes in moist air, ignites in air as powder or chips at 150 °C, and releases flammable hydrogen on contact with water (PubChem, HSDB)
Europium	Red phosphor activator in display and lamp phosphors (Y2O3:Eu, YVO4:Eu) and as the activator of strontium iodide scintillators for planetary gamma-ray spectroscopy (Wikipedia, PSI, arXiv 1111.5505)	Tarnishes quickly in air, reacts with water to release flammable hydrogen, and finely divided metal can ignite spontaneously (Ames SDS, Wikipedia)
Terbium (Tb)	Green phosphors for lighting and displays, and magnetostrictive Terfenol-D actuators (Wikipedia; NASA 1991 report)	Dust and fines that ignite, and metal that releases hydrogen on contact with water or dilute acid (Ames SDS, WebElements)
Holmium	Strong magnetic pole pieces and neutron absorption, where its 10.6 μB magnetic moment and strong neutron capture matter (Wikipedia, Goodfellow)	Fine powder that can ignite, and metal that releases flammable hydrogen on contact with water (Angstrom SDS, Prochem SDS)
Erbium	Optical fibre amplifiers, where erbium is the active dopant in silica fibre (Wikipedia)	Fine metal is flammable (PubChem H228), and the metal reacts with hot water and dilute acids and tarnishes in moist air (Wikipedia, Stanford Advanced Materials)
Thulium (Tm)	Thulium-doped 2 µm lasers (Tm:YAG and Tm fibre lasers) and the Tm-170 portable X-ray source (Goodfellow, Wikipedia)	Fine dust and chips that ignite, hydrogen release on contact with water or acid, and stiffness and strength figures that differ between sources (Ames SDS, Wikipedia, Goodfellow, WebElements)
Ytterbium (Yb)	Dopant for solid-state and fibre lasers, and reference data for a heavy rare-earth metal (NASA Goddard LISA laser; Wikipedia)	Fine powder that ignites in air, and metal that releases flammable gas on contact with water (Samat and Trace Sciences SDS, PubChem)
Lutetium	Lutetium-containing scintillators for PET detectors, where high density and a 50 ns decay matter (BNC LYSO datasheet)	Flammable as chips or powder, and it releases flammable gas on contact with water (PubChem GHS; ChemicalBook SDS, H260)
Yttrium	Phosphors and laser-crystal hosts, where yttrium is in the oxide or garnet form (USGS: no direct substitute in most electronics, laser and phosphor uses)	Fine powder and turnings, which ignite in air (Wikipedia, CRC) and react with water to release hydrogen (Apollo Scientific SDS). Its supply is 100 % import-dependent for the United States (USGS).
Scandium	Aluminium-scandium alloys for aerospace parts, where a small scandium addition refines grain and strengthens welds (Wikipedia; Zaki Ahmad, JOM 2003)	Availability and price: about 80 tonnes of oxide a year worldwide in 2025, and a scandium metal ingot price of 5,200 dollars per kg (USGS)