Rare Earth Elements in National Defense
Background on Rare Earth Elements
What Are Rare Earth Elements?
According to the U.S. Geological Survey (USGS),20 there are 17 rare earth elements on the periodic table. The first 15 elements begin with atomic number 57 (lanthanum) and extend through element number 71 (lutetium); two other elements, yttrium and scandium, have similar properties. Rare earths are not particularly rare but are found in low concentrations in the earth’s crust. The economics of locating and retrieving them are challenging. Rare earths are divided into two groups: light rare earth elements (LREE) - lanthanum, cerium, praseodymium, neodymium, promethium, and samarium, and heavy rare earth elements (HREE) - europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.
How Are Rare Earths Used in Defense Applications?
It has been estimated that DOD uses less than 5% of domestic consumption of rare earths.21 Rare earth elements are found in two types of commercially available, permanent magnet materials. They are samarium cobalt (SmCo), and neodymium iron boron (NdFeB). NdFeB magnets are considered the world’s strongest permanent magnets and are essential to many military weapons systems. SmCo retains its magnetic strength at elevated temperatures and is ideal for military technologies such as precision-guided missiles, smart bombs, and aircraft. The superior strength of NdFeB allows for the use of smaller and lighter magnets in defense weapon systems.
The following illustrations (Figures 1-5) show the use of rare earth elements in a variety of defense-related applications:
fin actuators in missile guidance and control systems, controlling the direction of the missile;
disk drive motors installed in aircraft, tanks, missile systems, and command and control centers;
lasers for enemy mine detection, interrogators, underwater mines, and countermeasures;
satellite communications, radar, and sonar on submarines and surface ships; and
optical equipment and speakers.
20 USGS Fact Sheet 087-02, and USGS Mineral Commodity Summaries, January 2010, http://pubs.usgs.gov/fs/2002/ fs087-02/.
21 Ratnam, Gopal. Rare Earth Shortage Would Spur Pentagon to Action. Bloomberg News, April 9, 2012, http://www.bloomberg.com/news/2012-04-09/rare-earths-shortage-would-spur-pentagon-to-action.html.
Congressional Research Service