Consider the following statements:

Statement I: Some rare earth elements are used in the manufacture of flat television screens and computer monitors.   

Statement II:  Some rare earth elements have phosphorescent properties.   

Which one of the following is correct?   

• Both are correct, and II explains I   
• Both are correct, but II does not explain I   
• Only I is correct   
• Only II is correct   

Answer: (a) Both are correct, and II explains I   

• Rare earth elements (REEs) are a group of 17 chemically similar elements, including the 15 lanthanides along with scandium and yttrium. These elements possess unique magnetic, luminescent, and electrochemical properties, making them essential in various high-tech applications, including electronics, renewable energy, and defense.
  • Despite the name, they are not rare but are hard to extract due to low concentration.
  • Properties & Uses: They possess unique magnetic, luminescent, and electrochemical properties. They are critical for permanent magnets (used in electric vehicles and wind turbines), catalysts, phosphors, and polishing compounds.
  • Production & Supply: China dominates the global supply chain, controlling approximately 60% of mining and 90% of processing, although deposits exist worldwide.
  • Sources: They are primarily mined from minerals such as bastnäsite, monazite, and ion-adsorption clays.
  • Geopolitics: Due to their importance in defence and tech, they are considered critical minerals, with many nations seeking to diversify supply chains away from Chinese dominance.
• Rare earth elements such as europium, terbium, and yttrium are integral in the production of phosphors used in display technologies. These phosphors emit specific colours when excited by electrons, enabling the vivid displays in flat-screen televisions and computer monitors. For instance, europium is used for red phosphors, terbium for green, and yttrium serves as a host lattice for these phosphors.
• Certain rare earth elements exhibit phosphorescence, a type of photoluminescence where materials emit light after being energized. Elements like europium and terbium are known for their phosphorescent properties, which are harnessed in various applications, including lighting and display technologies.
• The phosphorescent properties of rare earth elements are the reason they are used in manufacturing display screens. The ability of these elements to emit light upon excitation is fundamental to the functioning of phosphors in screens, thereby directly linking their phosphorescent nature to their application in display technologies.