Rare earth elements such as neodymium (Nd), samarium (Sm), gadolinium (Gd), dysprosium (Dy), europium (Eu), erbium (Er), yttrium (Y) and praseodymium (Pr) are important raw materials in a variety of electronics products, such as batteries, phosphors, drives, lighting, display, photovoltaic films and permanent magnets (found in motors, disk drives, smart phones and ear buds).
Over the past few years, shortages of rare earth supplies and rapidly rising prices have occurred because China provides most of the world’s rare earth elements and has decided to utilize their rare earth stores for domestic industries (see Global Rare Earth Oxide Mine Production from the U.S. Geological Survey). For additional in-depth information on rare earth materials, also see the IHS Chemical Economics Handbook section "Rare Earth Minerals and Products Report."
The rare earth shortage represents an opportunity for electronic materials researchers on two fronts. The first is developing alternative rare earth-free materials with suitable properties. The second is developing new mineral sources, improved extraction methods and recycling processes.
The 4f electron shielding in rare earth elements provides unique properties that are difficult to duplicate with alternative constituents. Researchers have had some success using processing and nanotechnology to develop alternative materials, and have also focused on eliminating or reducing the content requirements of specific rare earth element constituents.
Neodymium and dysprosium rare earth elements are essential constituents in neodymium (NdFeB) magnets used in disk drives, electric vehicle motors and wind turbine generators. NdFeB magnets are also important in magnetic sensors and disc drives. Dysprosium imparts high temperature properties to NdFeB magnets. Several materials researchers are looking for substitute materials.
For example, David Brown and his colleagues from the Magnequench Technology Center discussed at a recent conference work they have done to develop high temperature magnetic stability without dyprosium through a nano-scale microstructure produced by melt spinning and hot pressing. The need to increase production and sources of heavy rare earth elements (Nd, Dy and so on) for magnet manufacturing will result in greater quantities of the light rare earth elements (lanthanum, cerium among others) available for applications in displays, photonics and microelectronics.
In “The Uses of Rare Elements Activated Micrometer and Nanometer Sized Phosphor Particles in Modern Technology”, Jack Silver discussed an overview of applications for the rare earth element activated phosphor, including uses in displays, LEDs, fluorescent lamps, anti-counterfeiting markers, luminous paints and biomolecule probes. Europium rare earths were first used as display phosphors in 1960-vintage color televisions. Europium-doped yttria continues to be an important red phosphor, along with modified compositions with vanadium, sulfur, phosphorous or boron. Reducing phosphor particle size to the nanoscale range allows quantum confinement and reduces bulk defects, resulting in improved luminescence efficiency.
Demand for high resolution and high efficiency phosphors for flat panel displays was a prime driver behind the development of low voltage, rare earth, activated phosphors. Phosphors for converting blue LEDs to white light can cost $1,600/kg. The availability of metals such as arsenic, gallium, indium and the rare-earth elements cerium, europium, gadolinium, lanthanum, terbium and yttrium will continue to be a factor in the cost and expanded use of LEDs and LED semiconductors.
In a paper published in the Canadian Institute of Mining, Metallurgy and Petroleum's “Luminescent Lanthanides: Past, Present and Future,” Andries Meijerink discussed the emerging applications of up- and down–conversion rare earth phosphors in the spectral conversion of light for photovoltaic cells. This advancement could improve solar cell efficiencies by capturing energy from a wider range of the solar spectrum. Researchers are still searching for a narrow-band red phosphor that can be excited in the blue spectral for producing efficient, warm, white LEDs.
Early in 2014, the U.S. Senate Energy and Natural Resources committee held a hearing on the Critical Minerals Policy Act of 2013, introduced by Sen. Lisa Murkowski (R-Alaska). The bill directs the Interior Department to conduct a comprehensive national assessment of critical minerals and for the federal government to establish an analytical and forecasting capability to identify critical mineral market dynamics relevant to policy formulation.
Meanwhile, Molycorp’s Mountain Pass mine in California has reopened in an effort to reintroduce domestic U.S. sources of rare earth materials. Molycorp spent three years designing, engineering and constructing its rare earth processing facility to achieve environmental and energy efficiency standards. The Mountain Pass mine ranked among the world’s leading producer or rare earth minerals until the 1980s, when an influx of low-cost rare earth minerals from China, along with environmental issues forced the mine’s closure.
In Australia, Lynas Corp. is increasing production at its Mount Weld mine. The company also ramped up production at its advanced materials processing facility in Malaysia. In South Africa, Great Western Minerals is preparing its mine in Steenkampskraal for production.
New resources also are being identified and explored in Canada, North Korea and India. Companies like Elissa Resources continue to explore and develop new rare earth resources. However, a recent drop in rare earth prices prompted Elissa to develop a more lucrative gold mine instead of developing its Thor REE Project in Nevada.
While engineers and scientists will continue to look for lower cost alternatives for rare earths, the demand for rare earth elements will continue to expand due to their unique properties, which enable advanced display, motor, clean energy and electronics technologies. Future rare earth supply likely will be met by the development of new resources and rare earth recycling.