Rare Earth

Rare earth elements (REEs) refer to a group of 17 elements on the periodic table that have very similar electronic structures as well as physical and chemical properties. These 17 elements include 15 lanthanide series elements along with scandium and yttrium.

Scandium and yttrium are included because they depict very similar chemical and physical properties along with affinities with lanthanides. They are usually found in the same ore body as lanthanides.

Although REEs are plentiful in the earth's crust, they are termed rare earth elements because of the difficult nature of their extraction and purification process. Additionally, their low concentrations make their economically exploitable ore deposits very rare.

Extraction process

REEs are mined similar to other ores, such as steps involving mining rocks, separating ores from tailings (waste rock) and refining ores to extract the metal.

Though an additional step of separating REEs from each other is required, which is a cost-intensive, time-consuming, and difficult process.

Applications

REEs are essential to many high-tech industrial as well as devices and applications that we use in our daily lives. Electronics, clean energy, aerospace, automotive, and defence are among the key industrial application areas for REEs.

Luminescent and catalytic properties of REEs make them highly suitable for green products and high technology applications.

Global producers

As per data from the US Geological Survey, China is the world's largest producer of REEs. China accounted for almost 58% of the global production in 2020.

Some of the other key producers of REEs are the United States, Myanmar, Australia and Madagascar, accounting for ~39% of the worldwide output.

Properties

· Magnetic properties: REEs like neodymium (Nd), dysprosium (Dy), and samarium (Sm) are used in producing magnets for electric motors and turbines, aircraft and missile guidance systems, computer hard drives, etc.

They have large capacities for storing a large amount of magnetic energy compared to other magnetic elements. They are naturally magnetic; however, they lose their magnetic nature even at room temperature.

To overcome this issue, transition metals, such as iron or cobalt, are added to produce REEs alloys, thus retaining their magnetism at higher temperatures and increasing their magnetic strength.

· Luminescent properties: Some REEs like europium (Eu), yttrium (Y), erbium (Er), and neodymium (Nd) produce light when stimulated by electromagnetic radiation.

This property of REEs makes them highly sought-after for the manufacturing of LEDs and compact fluorescent light bulbs. Erbium-doped fibre amplifiers are used in high-capacity fibre-optic lines deployed for internet data transfer and long-distance telephone calls worldwide.

· Electrical properties: A mix of cerium (Ce), lanthanum (La), neodymium (Nd), and praseodymium (Pr) is termed mischmetal and is used to make the anode of nickel–metal hydride (NiMH) batteries used in hybrid cars and portable construction tools.

This mischmetal is cheaper than a normal anode as individual metals are not required to be separated from each other. It also enhances the battery's life span and keeps a higher energy density.

· Catalytic properties: Because of their electron structure and comparative abundance, cerium and lanthanum are commonly used as catalysts (accelerators) in many chemical reactions and processes.

For example, gasoline-powered cars use cerium in their catalytic converters. Lanthanum is used for crude oil refining by assisting fluid catalytic cracking in extracting useful hydrocarbons from crude oil.